@article{shah_grimes_oviedo-rondón_westerman_2014, title={Acidifier application rate impacts on ammonia emissions from US roaster chicken houses}, volume={92}, ISSN={1352-2310}, url={http://dx.doi.org/10.1016/j.atmosenv.2013.01.044}, DOI={10.1016/j.atmosenv.2013.01.044}, abstractNote={Due to its potential environmental and public health impacts, emissions of ammonia (NH3) as well as several other gases from US livestock farms may be regulated. Broiler houses are important sources of NH3 emissions. However, there are no emissions data from roaster (8–12 wk old broilers, ∼4 kg ea.) houses. Producers treat the litter in broiler houses with acidifiers, such as sodium bisulfate (SBS, NaHSO4) to reduce ammonia production and protect bird health. However, there is very little data on the effect of acidifiers, particularly at high application rates on ammonia emissions. The impact of different SBS application rates [High (0.95–1.46 kg m−2, whole house), Medium (0.73 kg m−2, whole house), Low (0.37–0.49 kg m−2, whole house), and Control (0.37–0.49 kg m−2, brood chamber)] on ammonia emissions was evaluated in commercial roaster houses over 22 months spanning eight flocks. Ammonia emission from each fan was measured with an acid scrubber that operated only when the fan operated. Emissions were calculated using >95% measured data with the rest being estimated using robust methods. Exhaust ammonia–N concentrations were inversely correlated with the SBS application rates. Emission rates on animal unit (AU, where 1 AU = 500 kg live-mass) basis (ER, g d−1 AU−1) were reduced by 27, 13, and 5%, respectively, in the High, Medium, and Low treatments vs. the Control treatment (mean: 100 g d−1 AU−1, range: 86–114 g d−1 AU−1). Emission rates for the Control treatment measured in this study on roasters were mostly higher than ERs in the literature. Differences in ERs are not only due to diet, environmental and management conditions, but also due to measurement methods.}, journal={Atmospheric Environment}, publisher={Elsevier BV}, author={Shah, Sanjay B. and Grimes, Jesse L. and Oviedo-Rondón, Edgar O. and Westerman, Philip W.}, year={2014}, month={Aug}, pages={576–583} }
 @article{shah_oviedo-rondon_grimes_westerman_campeau_2013, title={Acidifier dosage effects on inside ammonia concentrations in roaster houses}, volume={29}, DOI={10.13031/aea.29.9904}, abstractNote={Abstract. Ammonia (NH 3 ) in broiler houses can degrade bird performance. Acidifier such as, sodium bisulfate (SBS) applied to litter inside broiler houses can reduce NH 3 release and thus improve bird performance. While there are multiple studies on acidifier effects on inside NH 3 concentrations in broiler houses, there are no studies in roaster houses where big broiler birds are grown for 8 to 12 wk. The impact of different SBS application rates - High (1.46 kg/m 2 , whole house), Medium (0.73 kg/m 2 , whole house), Low (0.49 kg/m 2 , whole house), and Control (0.49 kg/m 2 , brood chamber) on inside NH 3 concentrations was evaluated over six flocks of roaster chickens (~4 kg ea.). Ammonia concentrations were measured with acid scrubbers that sampled air at two locations (mid-house, end-house) 0.15 m above the litter. Inside NH 3 concentrations were much higher in the cool-season versus warm-season flocks. Generally, higher acidifier application rates provided better NH 3 suppression. Ammonia concentrations were ≤10 ppm during brooding, as well as for the entire duration of most warm-weather flocks with the High and Medium treatments. In the Low treatment, NH 3 concentrations were ≤25 ppm during brooding but approached or exceeded 25 ppm with the Control treatment. During brooding, the High, Medium, and Low treatments resulted in significantly lower mid-house NH 3 concentrations of 3, 6, and 14 ppm, respectively, versus the Control treatment (24 ppm). For a 62-d flock, mid-house NH 3 concentrations were significantly lower in the High and Medium treatments versus the Control treatment; concentrations in the High, Medium, and Low treatments were reduced by 47%, 32%, and 20%, respectively, versus the Control treatment.}, number={4}, journal={Applied Engineering in Agriculture}, author={Shah, Sanjay and Oviedo-Rondon, E. O. and Grimes, J. L. and Westerman, P. W. and Campeau, D.}, year={2013}, pages={573–580} }
 @article{shah_westerman_grimes_oviedo-rondon_campeau_2013, title={Ancillary effects of different acidifier application rates in roaster houses}, volume={22}, ISSN={1056-6171 1537-0437}, url={http://dx.doi.org/10.3382/japr.2012-00693}, DOI={10.3382/japr.2012-00693}, abstractNote={SUMMARY High ammonia levels in broiler houses can reduce bird performance. Broiler producers commonly use acidifiers to reduce ammonia build-up. In addition to improving broiler performance, acidifiers can also provide other ancillary benefits such as reducing propane and electricity use and increasing cake (caked litter) N content. In this 2-yr study involving 9 flocks, 4 levels of an acidifier (sodium bisulfate) were applied to commercial roaster houses in eastern North Carolina. The control treatment had a sodium bisulfate application rate of up to 0.1 lb/ft2 to the brood chamber, whereas the high, medium, and low treatments had application rates of up to 0.3, 0.15, and 0.1 lb/ft2, respectively, to the whole house. No treatment effect was observed on propane or electricity use. However, compared with published studies involving smaller broilers, roasters required lesser amounts of propane and electricity. Linear regressions of propane and electricity use as a function of ambient temperature may help with decision making in roaster production. Brooding accounted for 88% of propane consumption. Reduced pH in the high treatment compared with the other treatments led to significantly higher ammonium concentration in the cake.}, number={3}, journal={The Journal of Applied Poultry Research}, publisher={Oxford University Press (OUP)}, author={Shah, S. B. and Westerman, P. W. and Grimes, J. L. and Oviedo-Rondon, E. O. and Campeau, D.}, year={2013}, month={Sep}, pages={565–573} }
 @article{oviedo-rondon_shah_grimes_westerman_campeau_2013, title={Live performance of roasters raised in houses receiving different acidifier application rates}, volume={22}, ISSN={1056-6171 1537-0437}, url={http://dx.doi.org/10.3382/japr.2012-00716}, DOI={10.3382/japr.2012-00716}, abstractNote={SUMMARY The reutilization of litter is currently a common practice in broiler production due to several environmental and economic factors. The application of litter amendments in broiler houses is a popular practice that can reduce ammonia emissions from recycled litter by converting them to nonvolatile ammonium. Sodium bisulfate (SBS) is one of the acidifiers frequently used in broiler houses. Broilers raised to 9 wk may require higher acidifier application rates to prevent unhealthy NH3 levels throughout the flock than broilers raised to smaller sizes. A study with 6 flocks of roasters was conducted under commercial conditions to evaluate 4 levels of SBS. In a farm with 8 houses, 4 treatments were evaluated. In the control treatment 0.49 kg/m 2 of SBS was applied to the brood chamber, whereas the low, medium, and high treatments received 0.49, 0.73, and 1.46 kg/m 2 , respectively, in the whole house. Data were obtained as the average of 2 houses with approximately 21,000 broilers per house in each of the 6 flocks evaluated. Results indicated no significant differences due to treatments on final average BW, FCR, mortality, or the majority of condemnation parameters. The significant reductions in NH3 levels observed in the whole flock across all 6 flocks receiving SBS treatments did not significantly improve broiler live performance or affect condemnations at the processing plant.}, number={4}, journal={The Journal of Applied Poultry Research}, publisher={Oxford University Press (OUP)}, author={Oviedo-Rondon, E. O. and Shah, S. B. and Grimes, J. L. and Westerman, P. W. and Campeau, D.}, year={2013}, month={Nov}, pages={922–928} }
 @article{shah_grimes_oviedo-rondon_westerman_campeau_2013, title={Nitrogen mass balance in commercial roaster houses receiving different acidifier application rates}, volume={22}, ISSN={["1537-0437"]}, DOI={10.3382/japr.2012-00704}, abstractNote={SUMMARY Broiler production has the potential to cause water and air pollution. Acidifiers such as sodium bisulfate (SBS) can reduce ammonia (NH3) emissions from broiler houses; NH3 is an important air pollutant that also affects bird health. Due to their longer grow-outs, roasters may require higher acidifier application rates to prevent unhealthy NH3 levels during the flock than ordinary broilers. Changes in NH3 emission with acidifier use may affect the partitioning of the input nitrogen (N) among the different N output pathways. Accounting for these output pathways through N mass balance provides a complete picture of N as it cycles through the roaster house. In a 2-yr study involving 9 flocks of roasters, 4 levels of SBS were applied to the litter in commercial roaster houses. Whereas the control treatment received up to 0.49 kg/ m 2 to the brood chamber, the high, medium, and low treatments received up to 1.46, 0.73, and 0.49 kg/m 2 , respectively, to the whole house. Ammonia-N emission decreased and N removed in cake and litter increased with SBS application rate. Nitrogen output components were averaged over the 4 treatments and expressed as percent of total N input or per unit mass of live weight (LW). Ammonia-N emission during grow-out, bird N exported, and cake and litter N removed accounted for 17.3% or 11.2 g/kg of LW, 38.9% or 25.1 g/kg of LW, and 22.4% or 14.4 g/kg of LW, respectively. We accounted for 79.1% of the total N inputs, with NH3-N losses during layout probably constituting the bulk of the unaccounted N. In addition to uncertainties in measurements of inputs and outputs, other factors that limited the ability to close the N mass balance were exclusion of feathers during cake and litter sampling, soil N leaching, and nitrous oxide emissions.}, number={3}, journal={JOURNAL OF APPLIED POULTRY RESEARCH}, author={Shah, S. B. and Grimes, J. L. and Oviedo-Rondon, E. O. and Westerman, P. W. and Campeau, D.}, year={2013}, month={Sep}, pages={539–550} }
 @article{yao_shah_willits_westerman_li_marshall_2011, title={Ammonia emissions from broiler cake stockpiled in a naturally ventilated shed}, volume={54}, DOI={10.13031/2013.39830}, abstractNote={Due to concerns about the negative environmental impacts of ammonia (NH3), the EPA may soon regulate NH3 emissions from livestock operations, including waste piles. This would require knowledge of NH3 emission rates, but there are very few field-scale studies on emission measurement from broiler waste stockpiles. This is the first study in which short-term NH3 fluxes from broiler cake stockpiled in a shed were measured, taking into account both forced and natural convection. Acid scrubbers were used to measure NH3 concentrations, while the integrated horizontal flux (IHF) method and Fick's law of diffusion were used to determine NH3 emissions due to forced and natural convection, respectively. Average daily air temperature and wind speed 0.75 m above the stockpile were 24.9°C and 0.65 m s-1 in summer and 8.5°C and 1.02 m s-1 in winter. Natural convection accounted for <0.01% of total emission, but not isolating gas concentrations during forced convection conditions generally led to overestimation of emission. In summer (7 d), NH3-N emission factors were 17 g m-2 d-1 (stockpile surface area), 30 g m-3 d-1 (stockpile volume), 1.8 g kg-1 N d-1 (initial cake N content), and 11 g AU-1 d-1 (where AU = 500 kg live weight marketed). During the first 7 d of the winter study, the emission factors were 27 g m-2 d-1, 43 g m-3 d-1, 2.1 g kg-1 N d-1, and 18 g AU-1 d-1, respectively. For the 15 d study, the emission factors changed very little. Higher emissions in winter were due to higher wind speeds, broiler cake total Kjeldahl N (TKN), and pH. While air temperature also affected emissions, stockpile temperatures (not measured) due to microbial activity were probably more important. Care should be taken in extrapolating this study's results to other stockpiles due to differences in stockpile dimensions, chemical properties, and environmental conditions.}, number={5}, journal={Transactions of the ASABE}, author={Yao, H. and Shah, Sanjay and Willits, D. H. and Westerman, P. W. and Li, L. W. and Marshall, T. K.}, year={2011}, pages={1893–1904} }
 @inproceedings{westerman_bowers_zering_2010, title={Phosphorus recovery from covered digester effluent with a continuous-flow struvite crystallizer}, volume={26}, DOI={10.13031/2013.29471}, abstractNote={Tests for phosphorus reduction by increasing magnesium and pH to form struvite (magnesium ammonium phosphate hexahydrate (MgNH4PO4 6(H2O)) were conducted using effluent from a covered earthen anaerobic digester for swine manure. A cone-shaped crystallizer system was constructed in the field and operated with direct pumping of covered digester liquid at a flow rate of 5.4 L/min (1.43 gal/min). Using the field system, 24 combinations of pH increase (0 to 1.5 pH units) and magnesium (Mg) addition (0, 20, 40, and 60 mg/L) were tested in short-term (30-min) tests. Up to 80% of the total phosphorus (TP) could be removed with the highest increases in pH and Mg. About 65% of TP was removed with the combination of 0.5-pH unit increase and addition of 40 mg/L of Mg. To test performance over longer periods, this combination was utilized in 40 tests each of 2-h duration during the period of September 2007 through October 2008. Reductions averaged 55 10% (mean standard deviation) removal of TP and 65 5% removal of orthophosphate phosphorus (OP). Analyses of samples of the solids removed from the crystallizer on six different dates indicated that N, P, and Mg were lower on average than theoretical values for pure struvite (5.71% N, 12.62% P, and 9.90% Mg) by 9.9%, 4.4%, and 6.2%. The solids included 1.8% calcium, indicating calcium compounds were being included in the formed material. Costs and returns were estimated for a commercial scale system and chemical costs and TP removal were estimated at selected levels of Mg addition and increase in pH. The net annual cost of the system for 60% removal of TP from digester effluent for a 1000-sow farrow-to-finish operation was estimated to be $0.0146/kg of live hog marketed.}, number={1}, booktitle={Applied Engineering in Agriculture}, author={Westerman, P. W. and Bowers, K. E. and Zering, Kelly}, year={2010}, pages={153–161} }
 @inproceedings{westerman_ogejo_grabow_2010, title={Swine anaerobic lagoon nutrient concentration variation with season, lagoon level, and rainfall}, volume={26}, DOI={10.13031/2013.29472}, abstractNote={Twenty swine anaerobic lagoons (8 finish, 6 nursery, and 6 sow) were monitored for lagoon liquid nutrient concentrations and liquid level above or below the stop-pump level. Weekly rainfall was also recorded. Significant differences in total nitrogen (N) concentrations existed between lagoons and also between types of farms. The N concentration varied within the same lagoon by a factor of two or more during the 4-yr study period and typically displayed a seasonal trend of decreasing during the summer and increasing during the winter. Years of operation (8 to 29 yr) were not a significant factor for mean N concentration over the 4-yr period. The lagoon liquid level was not a significant factor for N or total phosphorus (P) concentration. The finish farms displayed a decreasing trend of average annual nitrogen concentration with increase in annual rainfall.}, number={1}, booktitle={Applied Engineering in Agriculture}, author={Westerman, P. W. and Ogejo, J. A. and Grabow, G. L.}, year={2010}, pages={147–152} }
 @article{shah_balla_grabow_westerman_bailey_2009, title={Impact of land application method on ammonia loss from hog lagoon effluent}, volume={25}, DOI={10.13031/2013.29236}, abstractNote={Ammonia volatilization during land-application of hog lagoon effluent can adversely affect public health and the environment. Ammonia losses from hog lagoon effluent applied to Coastal Bermudagrass with the drag-hose (two applications) and traveling gun (three applications) were measured in spring and summer of 2006. Ammonia losses during application with the traveling gun were measured with acidified catch cans while losses during (traveling gun) or following (drag-hose) application for up to 96 h was measured with a micrometeorological method, the integrated horizontal flux (IHF) method; ammonia-N losses measured with the IHF method and catch cans are not additive. Ammonia-N losses during application with the traveling gun ranged between 3.8% to 9.2% of total ammoniacal nitrogen (TAN) applied, increasing with wind speed and decreasing relative humidity. For two applications, average ammonia loss with the drag-hose was <25% of the traveling gun. Ammonia-N losses from the traveling gun and drag-hose averaged 46.3% (n = 3) and 5.5% (n = 2), respectively, of the TAN applied. Ammonia-N loss during the first 4 h, as percent of total TAN loss was higher with the traveling gun. Whereas traveling gun ammonia losses were affected more by weather (e.g., relative humidity) and crop height, drag-hose losses were impacted more by effluent properties. Wind speed measurement contributed to <6% uncertainty in ammonia loss for both systems during one 4-h period. There are also other sources of uncertainty. Results from this study are comparable with published micrometeorological studies on hog lagoon effluent application.}, number={6}, journal={Applied Engineering in Agriculture}, author={Shah, Sanjay and Balla, B. K. and Grabow, G. L. and Westerman, P. W. and Bailey, D. E.}, year={2009}, pages={963–973} }
 @article{shah_westerman_munilla_adcock_baughman_2008, title={Design and evaluation of a regenerating scrubber for reducing animal house emissions}, volume={51}, DOI={10.13031/2013.24217}, abstractNote={Animal houses can emit substantial quantities of air pollutants. Compared with other pollutants, ammonia is emitted from animal houses in relatively large quantities and can have adverse public health and environmental impacts. This article describes the development and evaluation of a novel scrubber prototype, consisting of an endless polypropylene screen running in a trough of alum solution, that could be used to reduce ammonia emissions from animal houses. When building exhaust ventilation air contacts the screen, ammonia is dissolved in the aqueous solution on the screen and transported into the trough. Low ammonia concentration ( 66 h of evaluation under low and high concentration conditions, with a weighted average airflow rate of 0.93 m3 s-1 and velocity of 0.52 m s-1, the scrubber reduced ammonia emissions by 58.3%. Compared with commercial spray and packed column scrubbers used in industry, it had a lower pressure drop (~110 Pa). It also had a low water consumption of ~1 mL m-3 treated air. Further evaluation of the scrubber in different types of animal houses and for different pollutants is required. Its design should be improved to increase ammonia removal efficiency and reduce pressure drop, footprint size, and cost. There is also need to model gas transfer in this type of scrubber.}, number={1}, journal={Transactions of the ASABE}, author={Shah, Sanjay and Westerman, P. W. and Munilla, R. D. and Adcock, M. E. and Baughman, G. R.}, year={2008}, pages={243–250} }
 @article{blunden_aneja_westerman_2008, title={Measurement and analysis of ammonia and hydrogen sulfide emissions from a mechanically ventilated swine confinement building in North Carolina}, volume={42}, ISSN={["1352-2310"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-41449109456&partnerID=MN8TOARS}, DOI={10.1016/j.atmosenv.2007.06.040}, abstractNote={Emissions of atmospheric ammonia–nitrogen (NH3–N, where NH3–N=(1417)NH3) and hydrogen sulfide (H2S) were measured from a finishing swine confinement house at a commercial pig farm in eastern North Carolina. Continuous simultaneous NH3–N and H2S emissions were made for ∼1-week period during four different seasons. The number of pigs contained in the house varied from ∼850 to 900 with average weights ranging from ∼38 to 88 kg. Average NH3–N concentrations were highest during the winter and spring sampling periods, 8.91±4.61 and 8.44±2.40 ppm, respectively, and lower during the summer and fall, 2.45±1.14 and 4.27±0.71 ppm, respectively. Measured average H2S concentrations were 673±282, 429±223, 47±18, and 304±88 ppb during winter, spring, summer, and fall, respectively. Generally, the H2S concentrations were approximately an order of magnitude less than NH3–N during winter, spring, and fall, and two orders of magnitude smaller during the summer season. The average ambient temperature ranged from 5.5 to 22.3 °C while the average barn temperature measured at the outlet fans ranged from 19.0 to 26.0 °C in the winter and summer, respectively. The average fan ventilation rates varied from 253 m3 min−1 during the fall sampling period to 1024 m3 min−1 during summer. Calculated total emission rates for both NH3–N and H2S were highest during the spring, 4519±1639 g N day−1 and 481±142 g day−1, respectively. Emissions were lowest during the fall season for NH3–N (904±568 g N day−1) and the summer season for H2S (82±49 g day−1). Normalized NH3–N emission rates were highest in winter and spring (33.6±21.9 and 30.6±11.1 g N day−1 AU−1, where 1 AU (animal unit)=500 kg) and lowest during summer and fall (24.3±12.4 and 11.8±7.4 g N day−1 AU−1). Normalized H2S emissions were highest during the winter and spring seasons (4.2±2.1 and 3.3±1.0 g day−1 AU−1) and were lowest in summer and fall (1.2±0.7 and 1.7±0.5 g day−1 AU−1).}, number={14}, journal={ATMOSPHERIC ENVIRONMENT}, author={Blunden, Jessica and Aneja, Viney P. and Westerman, Phillip W.}, year={2008}, month={Apr}, pages={3315–3331} }
 @misc{griffing_overcash_westerman_2007, title={A review of gaseous ammonia emissions from slurry pits in pig production systems}, volume={97}, ISSN={["1537-5110"]}, DOI={10.1016/j.biosystemseng.2007.02.012}, abstractNote={Twenty-six experimental studies of ammonia emissions from pig buildings that utilise some form of pit/slurry system have been analysed and compared. Using standard values for pig weight and total Kjeldahl nitrogen (TKN) content in the waste when these quantities were unspecified, experimental ammonia emissions were compared on a per cent loss (of excreted TKN) basis. Correction factors were determined for measurements made during specific parts of the year, with corresponding differences in temperature, or time of day, and adjustments were made to put emission data on an annual average basis, when applicable. When corrected in this way, measurements made in the United States and in Europe were 22% and 21%, respectively. The standard deviation and standard error of the mean were 9% and 1.8%, respectively. The 95% confidence interval of the mean was 17.6–24.9%. The proposed emission factor data are reasonably consistent and emission factors higher or lower must be critically compared to the existing experimental base.}, number={3}, journal={BIOSYSTEMS ENGINEERING}, author={Griffing, E. M. and Overcash, M. and Westerman, P.}, year={2007}, month={Jul}, pages={295–312} }
 @article{saliling_westerman_losordo_2007, title={Wood chips and wheat straw as alternative biofilter media for denitrification reactors treating aquaculture and other wastewaters with high nitrate concentrations}, volume={37}, ISSN={["1873-5614"]}, DOI={10.1016/j.aquaeng.2007.06.003}, abstractNote={This study evaluated wood chips and wheat straw as inexpensive and readily available alternatives to more expensive plastic media for denitrification processes in treating aquaculture wastewaters or other high nitrate waters. Nine 3.8-L laboratory scale reactors (40 cm packed height × 10 cm diameter) were used to compare the performance of wood chips, wheat straw, and Kaldnes plastic media in the removal of nitrate from synthetic aquaculture wastewater. These upflow bioreactors were loaded at a constant flow rate and three influent NO3–N concentrations of 50, 120, and 200 mg/L each for at least 4 weeks, in sequence. These experiments showed that both wood chips and wheat straw produced comparable denitrification rates to the Kaldnes plastic media. As much as 99% of nitrate was removed from the wastewater of 200 mg NO3–N/L influent concentration. Pseudo-steady state denitrification rates for 200 mg NO3–N/L influent concentrations averaged (1360 ± 40) g N/(m3 d) for wood chips, (1360 ± 80) g N/(m3 d) for wheat straw, and (1330 ± 70) g N/(m3 d) for Kaldnes media. These values were not the maximum potential of the reactors as nitrate profiles up through the reactors indicated that nitrate reductions in the lower half of the reactors were more than double the averages for the whole reactor. COD consumption per unit of NO3–N removed was highest with the Kaldnes media (3.41–3.95) compared to wood chips (3.34–3.64) and wheat straw (3.26–3.46). Effluent ammonia concentrations were near zero while nitrites were around 2.0 mg NO2–N/L for all reactor types and loading rates. During the denitrification process, alkalinity and pH increased while the oxidation–reduction potential decreased with nitrate removal. Wood chips and wheat straw lost 16.2% and 37.7% of their masses, respectively, during the 140-day experiment. There were signs of physical degradation that included discoloration and structural transformation. The carbon to nitrogen ratio of the media also decreased. Both wood chips and wheat straw can be used as filter media for biological denitrification, but time limitations for the life of both materials must be considered.}, number={3}, journal={AQUACULTURAL ENGINEERING}, author={Saliling, Willie Jones B. and Westerman, Philip W. and Losordo, Thomas M.}, year={2007}, month={Nov}, pages={222–233} }
 @article{shah_grabow_westerman_2006, title={Ammonia adsorption in five types of flexible tubing materials}, volume={22}, DOI={10.13031/2013.22253}, abstractNote={Five different types of tubing materials, namely, polytetrafluoroethylene (PTFE), perfluoroalkoxy (PFA), fluorinated ethylene propylene (FEP), high density polyethylene (HDPE), and polyvinyl chloride (PVC) were evaluated for ammonia adsorption at two nominal ammonia concentration values (1 and 10 ppm) at ~24°C. All tubing sections were 2.5 m in length and 4.76 mm in i.d. except the HDPE which had an i.d. of 4.32 mm. Mass balance was used to determine ammonia (as ammonium-nitrogen (N)) adsorbed on the inside of the tubing versus the total N recovered in the tubing plus the gas scrubbers (primary and secondary). No tubing significantly differed in N adsorption. Averaged for both ammonia concentrations, N adsorption as percent of total N ranged from 0.15% (PVC) to 1.69% (FEP). Hence, the least expensive PVC tubing may represent the best option under conditions similar to those used in this study. The gas scrubber design used in this study had excellent trapping efficiency (>99%).}, number={6}, journal={Applied Engineering in Agriculture}, author={Shah, Sanjay and Grabow, G. L. and Westerman, P. W.}, year={2006}, pages={919–923} }
 @misc{shah_westerman_arogo_2006, title={Measuring ammonia concentrations and emissions from agricultural land and liquid surfaces: A review}, volume={56}, ISSN={["2162-2906"]}, DOI={10.1080/10473289.2006.10464512}, abstractNote={Abstract Aerial ammonia concentrations (C g) are measured using acid scrubbers, filter packs, denuders, or optical methods. Using C g and wind speed or airflow rate, ammonia emission rate or flux can be directly estimated using enclosures or micrometeorological methods. Using nitrogen (N) recovery is not recommended, mainly because the different gaseous N components cannot be separated. Although low cost and replicable, chambers modify environmental conditions and are suitable only for comparing treatments. Wind tunnels do not modify environmental conditions as much as chambers, but they may not be appropriate for determining ammonia fluxes; however, they can be used to compare emissions and test models. Larger wind tunnels that also simulate natural wind profiles may be more useful for comparing treatments than micrometeorological methods because the latter require larger plots and are, thus, difficult to replicate. For determining absolute ammonia flux, the micrometeorological methods are the most suitable because they are nonintrusive. For use with micrometeorological methods, both the passive denuders and optical methods give comparable accuracies, although the latter give real-time C g but at a higher cost. The passive denuder is wind weighted and also costs less than forced-air C g measurement methods, but it requires calibration. When ammonia contamination during sample preparation and handling is a concern and separating the gas-phase ammonia and aerosol ammonium is not required, the scrubber is preferred over the passive denuder. The photothermal interferometer, because of its low detection limit and robustness, may hold potential for use in agriculture, but it requires evaluation. With its simpler theoretical basis and fewer restrictions, the integrated horizontal flux (IHF) method is preferable over other micrometeorological methods, particularly for lagoons, where berms and land-lagoon boundaries modify wind flow and flux gradients. With uniform wind flow, the ZINST method requiring measurement at one predetermined height may perform comparably to the IHF method but at a lower cost.}, number={7}, journal={JOURNAL OF THE AIR & WASTE MANAGEMENT ASSOCIATION}, author={Shah, Sanjay B. and Westerman, Philip W. and Arogo, Jactone}, year={2006}, month={Jul}, pages={945–960} }
 @misc{bowers_westerman_2006, title={Method for removing phosphorus from waste lagoon effluent}, volume={7,005,072}, publisher={Washington, DC: U.S. Patent and Trademark Office}, author={Bowers, K. E. and Westerman, P. W.}, year={2006} }
 @article{bowers_westerman_2005, title={Design of cone-shaped fluidized bed struvite crystallizers for phosphorus removal from wastewater}, volume={48}, DOI={10.13031/2013.18504}, abstractNote={Precipitation of struvite in a cone-shaped fluidized bed crystallizer can efficiently remove excess phosphorus from 
wastewater. To enable design of such crystallizers, the mathematical relationships between the crystallizer performance and 
the design parameters are required. Such relationships, expressed in several design equations, were derived using material 
balances and a rate equation. The rate equation contains a constant whose value must be known in order to use the equation. 
A rate equation, including constant, has previously been reported for struvite precipitation. However, it is not suitable for 
deriving useful design equations because it treats neither the struvite constituent ion concentrations nor the reaction surface 
area separately, variables with which designers must deal explicitly. In the present work, the previously reported rate equation 
is revised into one that is more useful because it treats these variables specifically. The new rate equation is then used in 
deriving design equations for three alternative models, each based on different sets of assumptions about how the liquid and 
solid move in the crystallizer. The concentration profiles in a laboratory crystallizer were compared against profiles predicted 
by the design equations for each of the models at various values for the reaction constant. Predictions by one of the models, 
the PLMB (plug flow of liquid, mixed bed), fit the observed profiles with a rate constant of 10 to 15 dm h-1. It is recommended 
that design of similar crystallizers use the PLMB model and a rate constant in this range.}, number={3}, journal={Transactions of the ASAE}, author={Bowers, K. E. and Westerman, P. W.}, year={2005}, pages={1217–1226} }
 @article{westerman_bicudo_2005, title={Management considerations for organic waste use in agriculture}, volume={96}, ISSN={["1873-2976"]}, DOI={10.1016/j.biortech.2004.05.011}, abstractNote={Organic wastes are utilized in agriculture mainly for improving the soil physical and chemical properties and for nutrient sources for growing crops. The major source of organic waste used in agriculture is animal manure, but small amounts of food processing and other industrial wastes (along with municipal wastes) are also applied to land. In the last 35 years, and especially in the last 10 years, there have been increasing environmental regulations affecting farms that have resulted in more animal manure treatment options, and thus affecting characteristics of residues that are subsequently applied to land. Farms are being assessed for nutrient balances, with the entire nutrient and manure management system evaluated for best management alternatives. Because of inadequate available land on the animal farm in some cases, organic wastes must be treated and/or transported to other farms, or utilized for horticultural or other uses. This paper discusses the various factors and challenges for utilizing organic wastes in agriculture.}, number={2}, journal={BIORESOURCE TECHNOLOGY}, author={Westerman, PW and Bicudo, JR}, year={2005}, month={Jan}, pages={215–221} }
 @article{westerman_arogo_2005, title={On-farm performance of two solids/liquid separation systems for flushed swine manure}, volume={21}, DOI={10.13031/2013.18566}, abstractNote={Two different solids/liquid separation systems were evaluated for performance for six months on different farms 
with about 3500 finishing pigs each where barns were flushed two to four times a day with recycled anaerobic lagoon liquid. 
The two systems consisted of: (1) a screw-press separator followed by tangential flow separation (TFS) tanks, and (2) a screen 
and screw-press separator followed by TFS tanks. Sludge from the TFS units was recycled to input to the screw-press or the 
screw-press feed tank. As a percentage of input to the systems, the recoveries in separated solids were about 10% for total 
solids(TS), about 10% to 20% for suspended solids (SS), and about 1% to 4% for total Kjeldahl nitrogen (TKN) and total 
phosphorus (TP). Mass of moist solids (approximately 70% moisture content) removed per unit of flow was variable and 
averaged about 3 to 4 kg/m3 (25 to 33 lb/1000 gal). Moist separated solids averaged about 0.5% TKN and 0.1% to 0.2% TP. 
Concentrations reductions based on single grab samples taken every 2 to 3 weeks reflected performance of the various 
separation components, but did not agree well with the mass recoveries. The concentrations reductions through the TFS 
systems were similar for the two sites and showed 40% to 60% reduction for SS, TP, and several other parameters.}, number={4}, journal={Applied Engineering in Agriculture}, author={Westerman, P. W. and Arogo, J.}, year={2005}, pages={707–717} }
 @article{westerman_arogo_2005, title={Performance of a pond aeration system for treating anaerobic swine lagoon effluent}, volume={21}, DOI={10.13031/2013.18452}, abstractNote={The waste treatment system presented in this article is one of the alternative waste management systems that have 
been evaluated for swine farms in North Carolina. The treatment system was designed and installed on a commercial hog farm 
by International Ecological Systems and Services (IESS), Inc. The objectives of the treatment system were to reduce odor and 
ammonia emissions and nitrogen to be land applied. The treatment system consisted of an aeration pond with bacterial 
augmentation and was designed to treat 190 m3/d (50,000 gal/d) of swine anaerobic lagoon effluent. System performance was 
evaluated continuously over a 27-month period (Nov. 2000 to Jan. 2003). Nitrification, based on increased nitrite and nitrate 
concentrations in the aeration pond, varied with temperature. Dissolved oxygen (D.O.) concentrations during the last 18 
months of monitoring were usually 2 to 3 mg/L. Low D.O. sometimes occurred because of increased loading or loss of aeration 
due to broken belts on the blower or severed aeration lines. Based on the inflow and outflow concentrations of the aeration 
pond, total Kjeldahl nitrogen (TKN) and total ammoniacal nitrogen (TAN) reductions during the last 18 months of monitoring 
were 93% and 95%, respectively. The nitrate + nitrite nitrogen concentrations and the nitrite concentrations increased from 
near zero in inflow to the aeration pond to averages of 224 and 25 mg/L, respectively, in outflow during the last 18 months 
of monitoring. The treatment system experienced some operational and maintenance problems during the evaluation period, 
mainly with the bacteria delivery system, the blower, the flush tank plunger valves, and flushing controls. Effluent from the 
aeration pond had low odor intensity, usually low total ammonia nitrogen, variable amount of nitrate/nitrite nitrogen, and 
lower concentrations of phosphorus, copper, and zinc compared to the anaerobic lagoon effluent.}, number={3}, journal={Applied Engineering in Agriculture}, author={Westerman, P. W. and Arogo, J.}, year={2005}, pages={505–516} }
 @article{bowers_westerman_2005, title={Performance of cone-shaped fluidized bed struvite crystallizers in removing phosphorus from wastewater}, volume={48}, DOI={10.13031/2013.18523}, abstractNote={A struvite crystallizer design consisting of a continuously operating, cone-shaped fluidized bed was tested for its 
ability to remove phosphorus from swine lagoon liquid. A laboratory-scale apparatus was first tested, operating at 41 and 
57 L h-1 of lagoon liquid, and then a field-scale apparatus was tested, operating at 341 and 568 L h-1. Tests were arranged 
in a randomized complete block design, with the two cited lagoon liquid flow rates and three levels each of magnesium (Mg) 
supplementation and pH increase as independent variables. Levels of Mg supplementation were 0, 30, and 60 ppm. Ammonia 
was used to increase pH, and in the laboratory-scale tests, levels of this variable were set at 0, 100, and 200 ppm as nitrogen 
(N) of ammonia. In the field-scale tests, pH was controlled directly, and increased by 0, 0.5, and 1.0 pH units. In the 
laboratory-scale tests, orthophosphate phosphorus (OP) removal ranged from 1% to 80%, and total phosphorus (TP) removal 
ranged from -5% to 56%. In the field-scale tests, OP removal was 13% to 82%, and TP removal was 0% to 80%. The 
laboratory-scale apparatus exhibited greater removal with increasing Mg supplementation and pH augmentation, but flow 
rate showed no significant effect. The effects of the independent variables were similar in the field-scale apparatus, except 
that decreasing flow rate was associated with greater removal.}, number={3}, journal={Transactions of the ASAE}, author={Bowers, K. E. and Westerman, P. W.}, year={2005}, pages={1227–1234} }
 @article{arogo_westerman_heber_2003, title={A  review of ammonia emissions from confined swine feeding operations}, volume={46}, DOI={10.13031/2013.13597}, abstractNote={Ammonia emissions from swine feeding operations depend on the housing type; animal size, age, and type; manure 
management, storage, and treatment; climatic variables; and manure utilization or land application techniques. Techniques 
or methods for estimating or quantifying NH3 flux from a source to the atmosphere include nitrogen mass balance, 
micrometeorology, flux chambers, models, and emission factors. Of these techniques, emission factors, once established, 
provide the most convenience in estimating emissions. However,it is important to understand how a particular emission factor 
is determined and whether it accurately reflects a composite or average emission for all the variable conditons. Using an 
average ammonia emission factor multiplied by pig inventory to determine a regional or national ammonia emission inventory 
may be misleading, especially in the U.S. where existing emission factors were developed using data from swine facilities in 
Western Europe. 
Housing, manure management practices, and climate vary among different regions of the U.S. and can be very different 
from those in Western Europe. In addition, ammonia concentrations and emission estimations have been determined with a 
variety of methods, making it difficult to compare results. To determine representative ammonia emissions from confined swine 
feeding operations, it is important that emission factors be specific enough to account for animal type and size, housing 
system, manure storage and treatment, land application, and climatic effects. This article describes the strengths and 
limitations of emission factors as currently used and provides recommendations for determining realistic ammonia emission 
factors for swine feeding operations. Because of the limited nature of the data published in the literature, emission factors 
for different animal management systems could not be presented. 
Regulators, consultants, cooperative extension personnel, and other leaders in the agricultural community with interest 
in ammonia emissions should be aware of the lack of reliable U.S. data available for calculating accurate emission factors. 
The scientific research community should standardize methods for measurement, calculation, and reporting of ammonia 
emissions.}, number={3}, journal={Transactions of the ASAE}, author={Arogo, J. and Westerman, P. W. and Heber, A. J.}, year={2003}, pages={805–817} }
 @article{arogo_westerman_liang_2003, title={Comparing ammonium ion dissociation constant in swine anaerobic lagoon liquid and deionized water}, volume={46}, DOI={10.13031/2013.15441}, abstractNote={The dissociation constant of ammonium ion both in deionized water and swine anaerobic lagoon liquid was 
determined experimentally in a convective emission chamber at three temperatures (15.C, 25.C, and 35.C) commonly 
experienced in lagoons in the south and southeastern regions of the U.S. Ammonium chloride (NH4Cl) salt was used to make 
the solution for the deionized water tests. The dissociation constant (Kd) values obtained for NH4Cl in deionized water 
approximately doubled with every 10.C increase in liquid temperature from 15.C to 35.C. A similar trend was obtained for 
lagoon liquid in the 25.C to 35.C liquid temperature range, but the Kd values for the lagoon liquid were ~50% of those for 
NH4Cl in deionized water. However, at 15.C, the Kd value for the lagoon liquid was almost the same as for deionized water, 
and was 0.75 the lagoon liquid value at 25.C. Based on these results, it can be concluded that the Kd values of ammonium 
ion in anaerobic lagoon liquid was 50% of the value in deionized water at 25.C and 35.C, and 94% of the value at 15.C. 
This implies that for lagoons with characteristics similar to those of the anaerobic lagoon liquid reported in this study, the 
Kd values (normally derived from NH4 
+ dissociation in deionized water) used in ammonia volatilization calculations should 
be adjusted to a fraction of that in deionized water. More studies to determine the Kd values for lagoon liquids with different 
total ammonia nitrogen concentrations and solid contents are needed. Studies should include the effects of temperature and 
perhaps distinguish between the effects of dissolved and suspended solids on the dissociation constant.}, number={5}, journal={Transactions of the ASAE}, author={Arogo, J. and Westerman, P. W. and Liang, Z. S.}, year={2003}, pages={1415–1419} }
 @article{de visscher_harper_westerman_liang_arogo_sharpe_van cleemput_2002, title={Ammonia emissions from anaerobic swine lagoons: Model development}, volume={41}, DOI={10.1175/1520-0450(2002)041<0426:aefasl>2.0.co;2}, abstractNote={Concentrated animal production may represent a significant source for ammonia emissions to the environment. Most concentrated animal production systems use anaerobic or liquid/slurry systems for wasteholding; thus, it is desirable to be able to predict ammonia emissions from these systems. A process model was developed to use commonly available measurements, including effluent concentration, water temperature, wind speed, and effluent pH. The developed model simulated emissions, as measured by micrometeorological techniques, with an accuracy that explains 70% of the variability of the data using average daily emissions and explains 50% of the variability of the data using 4-h average data. The process model did not show increased accuracy over a statistical model, but the deviations between model and measurement were distributed more evenly in the case of the process model than in the case of the statistical model.}, number={4}, journal={Journal of Applied Meteorology}, author={De Visscher, A. and Harper, L. A. and Westerman, P. W. and Liang, Z. and Arogo, J. and Sharpe, R. R. and Van Cleemput, O.}, year={2002}, pages={426–433} }
 @article{westerman_bicudo_2002, title={Application of mixed and aerated pond for nitrification and denitrification of flushed swine manure}, volume={18}, DOI={10.13031/2013.8598}, abstractNote={A nitrification/denitrification system for flushed swine manure was evaluated for treating manure from 
3000 finishing pigs. The system consisted of a pond with a mixing zone for denitrification (anoxic) and an aeration zone for 
nitrification, with recirculation from aeration zone to mixing zone and also recycling from aeration zone to the barns for 
flushing. The system was designed by an engineering consulting firm and constructed, operated, and evaluated in cooperation 
with a swine production company and North Carolina State University as part of an effort by the North Carolina Governor’s 
Office to help fund demonstration and evaluation of innovative treatment technologies for swine manure. The process startup 
was not successful during winter with high loading (manure from 6750 finishing pigs), but was successful during summer with 
lower loading (manure from 3000 finishing pigs). Due to delays and funding limits for operation, the system was fully 
operational and monitored for only 16 weeks (28 July 

 
17 November 1998). After initial problems with foaming and the liner 
floating were addressed, the treatment system had good stability with relatively few operational problems. The estimated 
nitrogen reduction was between 65 and 90%, depending on estimation method. Reduction of nitrogen would be expected to 
decrease with lower temperature in winter. More than 90% of the effluent total nitrogen (N) was organic N. Odor perception 
ratings for intensity, irritation, and unpleasantness for liquid samples were significantly reduced by the treatment system. 
Approximately 78–kW (105–hp) energy use was required continuously, resulting in a high energy cost for operation.}, number={3}, journal={Applied Engineering in Agriculture}, author={Westerman, P. W. and Bicudo, J. R.}, year={2002}, pages={351–358} }
 @article{liang_westerman_arogo_2002, title={Modeling ammonia emission from swine anaerobic lagoons}, volume={45}, DOI={10.13031/2013.8859}, abstractNote={A mathematical model to estimate ammonia emission from anaerobic swine lagoons was developed based on the 
classical two–film theory. Inputs to the model are wind speed and lagoon liquid properties such as total ammonia nitrogen 
(TAN) concentration, pH, and temperature. Predicted emission rates of ammonia increase when any of these parameters are 
increased, but the relationship is linear only with TAN concentration. The dissociation constant (Kd) for ammonia in lagoon 
liquid is also an important factor, with higher flux predictions for higher Kd. The model was validated by comparing the model 
outputs to measured fluxes from two lagoons in North Carolina. The predicted ammonia emission fluxes for the two lagoons 
ranged from 1 to 38 kg NH3–N/ha–d, which was a wider range than the fluxes measured (2.5 to 22 kg N/ha–d) by other 
researchers using the micrometeorological method. 
Compared to measured fluxes at each lagoon, the model tended to predict higher ammonia fluxes at lagoon A and lower 
fluxes at lagoon B when a Kd of 0.5 was used. Additional information is needed regarding ammonia dissociation (Kd) values 
for anaerobic lagoon liquid. Comparison of the model results with a linear regression equation indicated that the model 
predicted much higher fluxes at temperatures above 25 
³ 
C and at upper ranges of pH and wind speed. Finally, the model was 
used with typical lagoon TAN concentration and pH, and average monthly values for wind speed and estimated liquid 
temperature at Raleigh, North Carolina, to predict monthly ammonia emissions for a typical anaerobic swine lagoon in North 
Carolina. The highest and lowest monthly ammonia emission occurred in June and January, respectively. Based on the 
average monthly emissions, it is estimated that the average annual ammonia nitrogen emission rate from the surface of a 
typical lagoon in North Carolina would be 234 g/m 2 or 2340 kg/ha. However, the model and results from other researchers 
indicate that ammonia emission can vary greatly.}, number={3}, journal={Transactions of the ASAE}, author={Liang, Z. S. and Westerman, P. W. and Arogo, J.}, year={2002}, pages={787–798} }
 @article{hill_kantardjieff_sobsey_westerman_2002, title={Reduction of enteric microbes in flushed swine wastewater treated by a biological aerated filter and UV irradiation}, volume={74}, ISSN={["1061-4303"]}, DOI={10.2175/106143002X139785}, abstractNote={An aerobic biofilter system was studied to assess its effectiveness for reducing enteric microbial indicators in flushed swine wastewater under different seasonal conditions. A laboratory‐scale, low‐pressure UV collimated beam apparatus was used to investigate the effectiveness of UV irradiation for inactivating enteric bacteria, coliphages, and bacterial spores in treated and untreated swine wastewater having unfiltered absorbances of 5 to 11 cm−1 and total suspended solids concentrations of 500 to 1200 mg/L. Fecal coliforms, Escherichia coli, enterococci, somatic coliphages, and male‐specific coliphages were reduced by 97 to 99% in the biofilter system when reactor water temperatures were between 23 and 32 °C. Salmonella were reduced by 95 to 97% when water temperatures were 17 to 32 °C. Of the six microbial indicators studied, Clostridium perfringens spores were typically reduced the least by the biofilter system. At an average absorbed UV irradiation dose of 13 mJ/cm 2 , maximum reductions of fecal coliforms, E. coli, enterococci, C. perfringens spores, and somatic coliphages in biofilter system effluent were 2.2, 2.1, 1.3, 0.2, and 2.3 log10, respectively. The results of this study show that the aerobic biofilter system can be an effective alternative for treatment of flushed swine waste. Ultraviolet irradiation can be effective for further reducing enteric microbe concentrations in biologically‐treated swine waste, as well as in lower quality wastewaters, indicating its general potential for pathogen reductions in low‐quality wastewaters intended for beneficial reuse.}, number={1}, journal={WATER ENVIRONMENT RESEARCH}, author={Hill, VR and Kantardjieff, A and Sobsey, MD and Westerman, PW}, year={2002}, pages={91–99} }
 @article{arogo_westerman_2000, title={Conceptual model for ammonia and odor production and ammonia emission from swine anaerobic lagoons}, ISBN={1892769123}, journal={Air pollution from agricultural operations : proceedings of the 2nd international conference, October 9-11, 2000, Des Moines, Iowa}, publisher={St. Joseph, Mich. : American Society of Agricultural Engineers}, author={Arogo, J. and Westerman, P. W.}, year={2000}, pages={132} }
 @article{classen_young_bottcher_westerman_2000, title={Design and analysis of a pilot scale biofiltration system for odorous air}, volume={43}, DOI={10.13031/2013.2675}, abstractNote={Three pilot-scale biofilters and necessary peripheral equipment were built to clean odorous air from the pit of a swine gestation building at North Carolina State University. A computer measured temperatures, flow rates, and pressure drops. It also controlled and measured the moisture content of a biofilter medium comprised of a 3:1 mixture of yard waste compost to wood chips mixture (by volume). The system was evaluated to ensure that the biofilters would be useful for performing scientific experiments concerning the reduction of swine odor on future research projects. The capability of the biofilters to remove odor was measured using a cotton swatch absorption method and an odor panel. The average odor reductions measured by odor intensity, irritation intensity, and unpleasantness for five tests were 61%, 58%, and 84%, respectively. No significant differences in odor reduction performance were found between the biofilters.}, number={1}, journal={Transactions of the ASAE}, author={Classen, John and Young, J. S. and Bottcher, R. W. and Westerman, P. W.}, year={2000}, pages={111–117} }
 @article{westerman_bicudo_2000, title={Tangential flow separation and chemical enhancement to recover swine manure solids, nutrients and metals}, volume={73}, ISSN={["0960-8524"]}, DOI={10.1016/S0960-8524(99)00148-0}, abstractNote={A mobile unit of a tangential flow separator (TFS) system was installed at a swine farm. System performance was evaluated through tests conducted on 11 different occasions between February and August of 1997 with flushed wastes and lagoon liquid. The TFS unit consists of a lime slurry tank, a pre-floc mixing tank, a TFS tank, a thickening tank and associated pumps and flow meters with a processing capacity of 110 m3/d. Previously screened wastes were mixed with lime in the pre-floc tank, ferric chloride and polymer injected into the flow after pre-floc tank, and flow introduced to the TFS tank tangentially to the wall, creating a circular motion within the tank. The fluid dynamics tends to concentrate solids to the center of the tank where they settle to the bottom. Approximately 75% of incoming flow are discharged at the top as treated effluent, with reduced organic and nutrient content, and flow to a storage lagoon. The settled solids that accumulate at the bottom of the TFS tank flow into a thickening tank of similar design to the main unit in order to further concentrate the solid material (up to 5% total solids). System performance expressed as percentage reduction is better when flushed wastes are processed compared to lagoon liquid. Total phosphorus (Total-P) removal can be higher than 90% depending on the amount of chemicals used. The system can remove an average of 22% total Kjeldahl nitrogen (TKN), 49% chemical oxygen demand (COD), 50% volatile solids (VS), 82% total suspended solids (TSS) and 87% copper (Cu) and zinc (Zn). Percentage reductions obtained with lagoon liquid are generally lower than with flushed wastes. However, the concentrations in effluent from the TFS system are lower for lagoon liquid than for flushed wastes. Typical concentrations of chemicals are about 2000 mg/l of hydrated lime, 400 mg/l of ferric chloride, and 20 mg/l of polymer. Chemical costs can be significant and must be balanced with improvements in effluent quality and potential economic value of sludge.}, number={1}, journal={BIORESOURCE TECHNOLOGY}, author={Westerman, PW and Bicudo, JR}, year={2000}, month={May}, pages={1–11} }
 @article{westerman_bicudo_kantardjieff_2000, title={Upflow biological aerated filters for the treatment of flushed swine manure}, volume={74}, ISSN={["0960-8524"]}, DOI={10.1016/S0960-8524(00)00028-6}, abstractNote={A pilot plant with capacity to treat up to 8 m3/day of supernate from settled flushed swine wastes was monitored for 12 months. The main system is composed of two upflow aerated biofilters connected in series. The aerated biofilters, operated under warm weather conditions (average temperature of 27°C), were able to remove about 88% of biochemical oxygen demand (BOD), 75% of chemical oxygen demand (COD), and 82% of total suspended solids (SS) with loading of 5.7 kg COD/m3/day of biofilter media. The total Kjeldahl nitrogen (TKN), total ammonia nitrogen (NH3-N), and total nitrogen (Total-N) reductions averaged 84%, 94% and 61%, respectively, during warm weather, with a significant portion of the NH3-N being converted to nitrite plus nitrate nitrogen (NO2+NO3-N). At higher organic loading (over 9 kg COD/m3/day) during September, the biofilters had only slightly lower percentage removal rates. Operation at lower temperatures (average of 10°C) resulted in lower performances. The COD, TKN, NH3-N, and Total-N removal averaged 56%, 49%, 52%, and 29%, respectively, in December through March. The COD mass removal rate was linear with loading rate over the range of approximately 2–12 kg COD/m3/day of filter. A mass balance average for the 12 months indicated that about 30% of the influent volume, 35% of Total-N and 60% of total phosphorus (Total-P) are removed with the biofilter backwash. Management and utilization of the backwash are important factors in implementing this type of system on farms. The unaccounted-for nitrogen was about 24% and could have been lost as ammonia volatilization or possibly through denitrification within the biofilm.}, number={3}, journal={BIORESOURCE TECHNOLOGY}, author={Westerman, PW and Bicudo, JR and Kantardjieff, A}, year={2000}, month={Sep}, pages={181–190} }
 @article{bicudo_safley_westerman_1999, title={Nutrient content and sludge volumes in single-cell recycle anaerobic swine lagoons in North Carolina}, volume={42}, DOI={10.13031/2013.13256}, abstractNote={Fifteen single-stage anaerobic lagoons representing four types of swine production farms (farrow-to-feeder, 
crossing, farrow-to-finish, and finish) were monitored during two years to evaluate performance. Lagoon liquid and 
sludge were characterized for all sites. Lagoon loading rates, percent of lagoon volume occupied by sludge, sludge 
accumulation and age of lagoon at the time of evaluation were determined. The mean annual lagoon liquid Total Kjeldahl 
Nitrogen (TKN) increased with increase in average daily live animal weight per cubic meter (LAW/m3) of lagoon volume, 
and the rate of increase depended upon the type of production farm. The monthly supernatant TKN concentration varied 
as much as 50% over two years for the same lagoon, generally showing a cyclic pattern with highest concentration in 
mid-summer. Of the nutrient mass contained in the lagoon, about 30% of TKN and more than 90% of Total Phosphorus 
(Total-P) and volatile solids (VS) were contained in the sludge. The accumulation of TKN and Total-P in the sludge 
increased linearly with time. Sludge accumulation was found to be impacted both by age of lagoon and loading rate. 
Based on total sludge accumulated and the age of lagoon, it was determined that sludge accumulated at an approximate 
rate of 0.003 m3/yr per kg of LAW. This is higher accumulation rate than reported from a study in Missouri, but lower 
than reported by a study in South Carolina. It is approximately 25% of the value predicted by ASAE Engineering Practice 
EP 403.2 and ASAE DATA D384.1. Additional data is needed on sludge accumulation rates in swine lagoons and 
characterization of sludge, especially considering likely changes in swine nutrition to improve nutrient utilization and 
reduce nitrogen and phosphorus excretion.}, number={4}, journal={Transactions of the ASAE}, author={Bicudo, J. R. and Safley, L. M. and Westerman, P. W.}, year={1999}, pages={1087–1093} }
 @article{westerman_zhang_1997, title={Aeration of livestock manure slurry and lagoon liquid for odor control: a review}, volume={13}, DOI={10.13031/2013.21596}, abstractNote={Odors can be generated on livestock production farms from three major sources: production facilities, waste 
treatment system and land application. Aerobic treatment of animal manure slurry and lagoon liquid can be an effective 
treatment for odor control. The energy costs required for aeration, however, is a major factor that has prevented aerobic 
treatment from being used widely for livestock manure treatment. There are many different aeration devices and several 
possible aeration schemes and processes which can be used on livestock farms. Recent research has been focused on 
developing more efficient aeration techniques and equipment, determining the minimum aeration requirements for odor 
control, and developing optimum intermittent aeration schemes to obtain efficient manure decomposition and to effect 
nitrogen transformation and removal from the manure slurry or liquid. This article reviews the basic concepts of aerobic 
treatment and presents general recommendations for designing and operating various aeration systems for treating 
animal manure slurry and lagoon liquid.}, number={2}, journal={Applied Engineering in Agriculture}, author={Westerman, P. W. and Zhang, R. H.}, year={1997}, pages={245–249} }
 @article{twarowska_westerman_losordo_1997, title={Water treatment and waste characterization evaluation of an intensive recirculating fish production system}, volume={16}, DOI={10.1016/S0144-8609(96)01022-9}, abstractNote={A combination of two different technologies used for fish production was evaluated at the North Carolina State University (NCSU) F̀ish Barn facility. The combined system included the ECOFISH∗ tank, developed at the Norwegian Hydrotechnical Laboratory (NHL) at SINTEF (Trondheim, Norway) and water treatment and recycle technology designed at NCSU. Approximately 2170 fingerling tilapia (Oreochromis niloticus, Oreochromis niloticus × Oreochromis aureus) were grown from 3.6 to 507 g in 177 days in a 20 m3 four-zone tank. The system design included patented particle traps at the bottom of each zone to remove feed waste and excrement, sludge collectors where the removed particles settled, a rotating screen filter for suspended solids removal, a high-rate linear-path trickling biological filter for nitrification, and two down-flow columns for oxygen injection. The measured suspended solids level in the tank zones were usually less than 7.5 mg l −1. Based on six efficiency tests with a mean total ammonia nitrogen (TAN) concentration in the culture tank of 0.62 mg l −1, the biofilter removed approximately 65% on a single pass through the filter, with an average removal rate per unit of filter surface area of 0.33 g TAN m −2 day −1. Sampling every 4 h over a 24-h period showed variability in concentrations and TAN removal rates by the biofilter. Six efficiency tests on the sludge collectors and the screen filter showed 80% and 41% suspended solids removal efficiency, respectively, based on the influent and effluent concentrations. On a daily basis, the sludge collectors and the screen filter each removed about 18% of feed volatile solids input, respectively, based on three 24-h periods studied. Fresh water use averaged approximately 1500 l day −1, which was about 7% of the system volume.}, number={3}, journal={Aquacultural Engineering}, author={Twarowska, J. G. and Westerman, P. W. and Losordo, T. M.}, year={1997}, pages={133–147} }
 @article{westerman_losordo_wildhaber_1996, title={Evaluation of various biofilters in an intensive recirculating fish production facility}, volume={39}, DOI={10.13031/2013.27556}, abstractNote={Various types and combinations of biofilters were evaluated in an operating, full-scale intensive recirculating fish production facility. Each of four tanks (18 900 L each) had a different combination of biofilters: 1) four upflow sand filters; 2) one upflow sand filter and two fluidized bed sand filters; 3) two prototype floating-bead filters; and 4) one upflow sand filter and one rotating biological contactor (RBC). The performance evaluation included the efficiency of each filter in removing total ammonia nitrogen (TAN), nitrite nitrogen (NO2-N), and suspended solids (SS). Removal was based on samples of the inflow and outflow of each filter taken once per day, two days per week for several weeks. Other water quality parameters measured were pH, alkalinity, carbon dioxide (CO2), and dissolved oxygen (DO).}, number={2}, journal={Transactions of the ASAE}, author={Westerman, P. W. and Losordo, T. M. and Wildhaber, M. L.}, year={1996}, pages={723} }
 @article{westerman_huffman_feng_1995, title={Swine-lagoon seepage in sandy soil}, volume={38}, DOI={10.13031/2013.28002}, abstractNote={Swine manure anaerobic lagoons have sometimes been constructed in sandy soil without clay liners. Although swine manure and other animal manures have been reported to physically “seal” lagoons to various degrees, long-term studies with sandy soil have been lacking. Two swine manure, anaerobic lagoons located in sandy, coastal plain soil were investigated. Both continued to have significant seepage after 3.5 to 5 years of receiving waste. Monitoring wells indicated broad seepage plumes, and much variation in concentrations of several parameters with well location, time, and depth of well. The variations indicate the difficulty of accurately monitoring and quantifying seepage transport of nutrients, and the complexity of developing groundwater transport models to accurately predict transport and transformations of chemical compounds, particularly ammonium and nitrate nitrogen, at various distances from the lagoon.}, number={6}, journal={Transactions of the ASAE}, author={Westerman, P. W. and Huffman, R. L. and Feng, J. S.}, year={1995}, pages={1749} }
 @article{westerman_overcash_evans_king_burns_cummings_1985, title={SWINE LAGOON EFFLUENT APPLIED TO COASTAL BERMUDAGRASS .3. IRRIGATION AND RAINFALL RUNOFF}, volume={14}, ISSN={["0047-2425"]}, DOI={10.2134/jeq1985.00472425001400010004x}, abstractNote={Abstract}, number={1}, journal={JOURNAL OF ENVIRONMENTAL QUALITY}, author={WESTERMAN, PW and OVERCASH, MR and EVANS, RO and KING, LD and BURNS, JC and CUMMINGS, GA}, year={1985}, pages={22–25} }
 @article{westerman_burns_king_evans_safley_1983, title={Effects of applying swine lagoon effluent to Coastal Bermudagrass at high rates for ten years}, number={2123}, journal={Paper (American Society of Agricultural Engineers)}, author={Westerman, P. W. and Burns, J. C. and King, L. D. and Evans, R. O. and Safley, L. M.}, year={1983}, pages={32} }
 @inbook{westerman_overcash_1981, title={Short-term attenuation of runoff pollution potential for land-applied swine and poultry manure}, ISBN={9780916150297}, booktitle={Livestock waste, a renewable resource : proceedings / 4th International Symposium on Livestock Wastes, 1980, April 15-17, 1980, Amarillo Civic Center, Amarillo, Texas}, publisher={St. Joseph, Mich.: American Society of Agricultural Engineers}, author={Westerman, P. W. and Overcash, M. R.}, year={1981}, pages={289} }