Effect of Acid Flow Rate, Membrane Surface Area, and Capture Solution on the Effectiveness of Suspended GPM Systems to Recover Ammonia.

Ammonia losses from manure pose serious problems for ecosystems and human and animal health. Gas-permeable membranes (GPMs) constitute a promising approach to address the challenge of reducing farm ammonia emissions and to attain the EU's Clean Air Package goals. In this study, the effect of NH3-N concentration, membrane surface area, acid flux, and type of capture solution on ammonia recovery was investigated for a suspended GPM system through three experiments, in which ammonia was released from a synthetic solution (NH4Cl + NaHCO3 + allylthiourea). The effect of two surface areas (81.7 and 163.4 cm2) was first evaluated using three different synthetic N emitting concentrations (3000, 6000, and 12,000 mg NH3-N∙L-1) and keeping the flow of acidic solution (1N H2SO4) constant (0.8 L·h-1). A direct relationship was found between the amount of NH3 captured and the NH3-N concentration in the N-emitting solution, and between the amount of NH3 captured and the membrane surface area at the two lowest concentrations. Nonetheless, the use of a larger membrane surface barely improved ammonia capture at the highest concentration, pointing to the existence of other limiting factors. Hence, ammonia capture was then studied using different acid flow rates (0.8, 1.3, 1.6, and 2.1 L∙h-1) at a fixed N emitting concentration of 6000 mg NH3-N∙L-1 and a surface area of 122.5 cm2. A higher acid flow rate (0.8-2.1 L∙h-1) resulted in a substantial increase in ammonia absorption, from 165 to 262 mg of NH3∙d-1 over a 14-day period. Taking the parameters that led to the best results in experiments 1 and 2, different types of ammonia capture solutions (H2SO4, water and carbonated water) were finally compared under refrigeration conditions (at 2 °C). A high NH3 recovery (81% in 7 days), comparable to that obtained with the H2SO4 solution (88%), was attained when chilled water was used as the capture solution. The presented results point to the need to carefully optimize the emitter concentration, flow rate, and type of capture solution to maximize the effectiveness of suspended GPM systems, and suggest that chilled water may be used as an alternative to conventional acidic solutions, with associated savings.

Pilot-Scale Demonstration of Membrane-Based Nitrogen Recovery from Swine Manure.

Gas-permeable membranes technology presents a high potential for nitrogen (N) recovery from wastewaters rich in ammonia (NH3). The EU project Ammonia Trapping (AT) is aimed at transferring knowledge from the lab-scale level to on-farm pilot-scale level, using this technology to recover NH3 from livestock wastewaters. The goal of this study is to report the results of an on-farm pilot-scale demonstration plant using gas-permeable membranes to recover N from raw swine manure. After a setup optimization of the plant, stable, and continuous operation was achieved. The maximum NH3 recovery rate obtained was 38.20 g NH3-N m-2 membrane day-1. This recovery rate was greatly affected by the temperature of the process. In addition to its contribution to NH3 emissions reduction, this technology contributes to the recovery of nutrients in the form of a concentrated stable ammonium sulphate solution. This solution contained 3.2% of N, which makes it suitable for fertigation. The economic approach revealed an economic feasibility of the technology, resulting in a cost of 2.07 € per kg N recovered.

Microbial characteristics of nitrifiers, denitrifiers and anammox bacteria on different support media to treat space mission wastewater.

Biomass attachment and growth are important factors for the startup and stability of fixed-film biological reactors being proposed to recycle wastewater for potable water use in manned space activity. Eight different biofilm support media commonly used in wastewater treatment plants, aquaculture, and aquariums were compared for their relative ability to support attachment and growth of nitrifiers, denitrifiers, and anaerobic ammonia oxidizing (anammox) bacteria biomass. Accumulated total biomass was determined by comparing dry weight of each media before and after culturing of biomass. Fluorescence In-Situ Hybridization (FISH) analysis was used to quantify the proportion and relative activity of each organism group on each media. Measurements of dry biomass normalized to several media properties showed polyether polyurethane foam to have the highest extent of specific biomass attachment and colonization. Six of the eight media were able to sustain a population of anammox bacteria that was more abundant than the other cohorts.

Improved water quality and reduction of odorous compounds in anaerobic lagoon columns receiving pre-treated pig wastewater.

Large volumes of wastewater from confined pig production are stored in anaerobic lagoons. Control methods are needed to reduce air pollution by foul odors released from these lagoons. In a pilot-scale experiment, we evaluated the effect of pig wastewater pre-treatment on reducing the concentration of selected malodor compounds in lagoons receiving liquid from: (1) flocculant enhanced solid-liquid separation (SS), and (2) solid-liquid separation plus biological N treatment using nitrification-denitrification (SS+NDN). A conventional anaerobic lagoon was included as a control. Concentrations of five selected malodorous compounds (phenol, p-cresol, 4-ethylphenol, indole, and skatole) and water quality parameters (ammonia-nitrogen and chemical oxygen demand) were determined in lagoon effluents. The SS+NDN pretreatment was more efficient than the SS in reducing odorous compounds in the lagoon liquid. The SS+NDN reduced by about 99% the liquid concentrations of all selected compounds. An odor panel test revealed that SS was ineffective to reduce the human sense of malodor with respect to the control. Whereas the SS+NDN had the significant lowest odor intensity and unpleasantness. These results are supported by the strong correlations found between the sum of odorous compound concentration with odor panel results and concentrations of both ammonium-nitrogen and chemical oxygen demand in lagoon liquid samples.

Phosphorus recovery from pig manure solids prior to land application.

Land disposal of pig manure is an environmental concern due to an imbalance of the nitrogen to phosphorus (N:P) ratio for crop production, leading to excess phosphorus (P) in soils and potential risks of water pollution. A process called "quick wash" was investigated for its feasibility to extract and recover P from pig manure solids. This process consists of selective dissolution of P from solid manure into a liquid extract using mineral or organic acid solutions, and recovery of P from the liquid extract by adding lime and an organic polymer to form a P precipitate. Laboratory tests confirmed the quick wash process selectively removed and recovered up to 90% of the total (TP) from fresh pig manure solids while leaving significant amounts of nitrogen (N) in the washed manure residue. As a result of manure P extraction, the washed solid residue became environmentally safer for land application with a more balanced N:P ratio for crop production. The recovered P can be recycled and used as fertilizer for crop production while minimizing manure P losses into the environment.

Water quality and nitrogen mass loss from anaerobic lagoon columns receiving pretreated influent.

Control methods are needed to abate NH losses from swine anaerobic lagoons to reduce the contribution of confined swine operations to air pollution. In a 15-mo meso-scale column study, we evaluated the effect of manure pretreatment on water quality, reduction of N losses, and sludge accumulation in swine lagoons using (i) enhanced solid-liquid separation with polymer (SS) and (ii) solid-liquid separation plus biological N treatment using nitrification-denitrification (SS + NDN). A conventional anaerobic lagoon was included as a control. Concentrations of total Kjeldahl N (TKN), total ammoniacal N (TAN), and NO-N were monitored during the course of the study, and the volumes of column liquid and sludge were used to estimate N mass flows. At the end of the study, TKN and TAN concentrations in the liquid of SS columns were 35 and 37% lower than the control, respectively, and TKN and TAN concentrations in SS + NDN were 97 and 99% lower than the control. The N mass flow analysis revealed that SS reduced total N inflow by 30% and SS + NDN by 82% compared with the control. The SS was ineffective at reducing NH losses compared with the control. Instead, SS + NDN effectively reduced total NH losses by 50%, most of which occurred during the first 6 mo of the study. Although both pretreatments can stop the mass accumulation of total N in sludge, SS + NDN had the advantage of improving water quality and abating NH emissions from treated lagoons. As an additional environmental benefit, SS + NDN effluents could be used for crop irrigation without the risk of NH losses during land application.

Partial nitritation of swine wastewater in view of its coupling with the anammox process.

Partial nitritation (PN) of swine wastewater was investigated in a sequencing batch reactor (SBR) using a high-performance nitrifying sludge. Characteristics of the wastewater used were low content of biodegradable organic matter and a high alkalinity-to-ammonium ratio. The target oxidation of ammonium nitrogen (NH-N) to nitrite nitrogen (NO-N) was 57% (1.32 g NO-N g NH-N), which corresponds with the reaction ratio of the anaerobic ammonium oxidation (anammox). This target was successfully achieved at 32°C by controlling the inflow rate and the corresponding nitrogen loading rate (NLR). An average NLR of 1.47 g NH-N L d was applied to the partial nitritation sequencing batch reactor during a period of 70 d. The nitrite production rate obtained was 0.91 g NO-N L d. No nitrate was produced. The PN effluent contained 1.38 g NO-N g NH-N, which was within 5% of the target ratio. Under steady composition of the wastewater, the pH was shown to be a good indicator of the PN process performance. Furthermore, in a second sequencing batch reactor, the anaerobic ammonium oxidation process was effectively applied to the PN effluent, attaining a nitrogen conversion rate of 0.36 g N L d (14.3 mg N g volatile suspended solids h).

Anammox sludge immobilized in polyvinyl alcohol (PVA) cryogel carriers.

This study evaluated the use of PVA cryogels to encapsulate slow-growing anammox bacteria for deammonification treatment of wastewater. The cryogel pellets were prepared by freezing-thawing at -8 °C. On average, pellets contained 11.8 mg-TSS/g-pellet of enriched anammox sludge NRRL B-50286 (Candidatus Brocadia caroliniensis) in 4-mm cubes. They were tested with synthetic and partially nitrified swine wastewater using continuous stirred-tank reactors packed at 20% (w/v). The immobilized gel was retained inside the reactor by a screen that eliminated the need of sludge recycling. The stoichiometry of anammox reaction was maintained for more than 5 months under non-sterile conditions. The process was not limited by substrates availability unless quite low N concentration (<5 mg/L) achieving >93% removal efficiency. In mass balances, >80% of the potential N conversion activity was achieved (2920 mg-N/kg-pellet/d). In addition, the immobilized bacteria were resilient to inhibition at high nitrite concentrations (244-270 mg-N/L).

Long-term preservation of anammox bacteria.

Deposit of useful microorganisms in culture collections requires long-term preservation and successful reactivation techniques. The goal of this study was to develop a simple preservation protocol for the long-term storage and reactivation of the anammox biomass. To achieve this, anammox biomass was frozen or lyophilized at two different freezing temperatures (-60°C and in liquid nitrogen (-200°C)) in skim milk media (with and without glycerol), and the reactivation of anammox activity was monitored after a 4-month storage period. Of the different preservation treatments tested, only anammox biomass preserved via freezing in liquid nitrogen followed by lyophilization in skim milk media without glycerol achieved stoichiometric ratios for the anammox reaction similar to the biomass in both the parent bioreactor and in the freshly harvested control treatment. A freezing temperature of -60°C alone, or in conjunction with lyophilization, resulted in the partial recovery of the anammox bacteria, with an equal mixture of anammox and nitrifying bacteria in the reactivated biomass. To our knowledge, this is the first report of the successful reactivation of anammox biomass preserved via sub-zero freezing and/or lyophilization. The simple preservation protocol developed from this study could be beneficial to accelerate the integration of anammox-based processes into current treatment systems through a highly efficient starting anammox biomass.

Characterization of a microbial community capable of nitrification at cold temperature.

While the oxidation of ammonia is an integral component of advanced aerobic livestock wastewater treatment, the rate of nitrification by ammonia-oxidizing bacteria is drastically reduced at colder temperatures. In this study we report an acclimated lagoon nitrifying sludge that is capable of high rates of nitrification at temperatures from 5 degrees C (11.2mg N/g MLVSS/h) to 20 degrees C (40.4 mg N/g MLVSS/h). The composition of the microbial community present in the nitrifying sludge was investigated by partial 16S rRNA gene sequencing. After DNA extraction and the creation of a plasmid library, 153 partial length 16S rRNA gene clones were sequenced and analyzed phylogenetically. Over 80% of these clones were affiliated with the Proteobacteria, and grouped with the beta- (114 clones), gamma- (7 clones), and alpha-classes (2 clones). The remaining clones were affiliated with the Acidobacteria (1 clone), Actinobacteria (8 clones), Bacteroidetes (16 clones), and Verrucomicrobia (5 clones). The majority of the clones belonged to the genus Nitrosomonas, while other clones affiliated with microorganisms previously identified as having floc forming or psychrotolerance characteristics.

Evaluation of second-generation multistage wastewater treatment system for the removal of malodors from liquid swine waste.

Wastewater quality and malodors in a second generation implementation of environmentally superior technology (EST) were monitored over three cycles of pig (Sus scrofa) production and 15 mo. The wastewater treatment system consisted of three modules: solids separation, biological N removal, and P recovery/wastewater disinfection. While approximately more than 90% of the wastewater suspended solids were removed in the first stage of treatment, little reduction in malodorous compounds occurred, indicating that malodors largely remained with the liquid waste stream. The greatest improvements in wastewater quality occurred in the N treatment module where ammonium was removed through nitrification/denitrification processes: there was more than 99% reduction in aromatic malodorous compounds (e.g., p-cresol, skatole) and almost 90% reduction in volatile fatty acids (e.g., propanoate and butanoate) in N module effluent as compared to raw flushed manure. The system performed consistently well in wastewater odor removal, even during the first cycle of livestock production when system performance was being optimized. These findings showed that the combination of the processes of solids removal and biological N treatment into a practical treatment system can be very effective in reducing malodors from livestock wastewater.

Bioenergy from Coastal bermudagrass receiving subsurface drip irrigation with advance-treated swine wastewater.

Coastal bermudagrass (Cynodon dactylon L.) may be a potentially important source of bio-based energy in the southern US due to its vast acreage. It is often produced as part of a waste management plan with varying nutrient composition and energy characteristics on fields irrigated with livestock wastewater. The objective of this study was to determine the effect of subsurface drip irrigation with treated swine wastewater on both the quantity and quality of bermudagrass bioenergy. The treated wastewater was recycled from an advanced treatment system and used for irrigation of bermudagrass in two crop seasons. The experiment had nine water and drip line spacing treatments arrayed in a randomized complete block-design with four replicates. The bermudagrass was analyzed for calorific and mineral contents. Bermudagrass energy yields for 2004 and 2005 ranged from 127.4 to 251.4MJ ha(-1). Compared to irrigation with commercial nitrogen fertilizer, the least biomass energy density was associated with bermudagrass receiving treated swine wastewater. Yet, in 2004 the wastewater irrigated bermudagrass had greater hay yields leading to greater energy yield per ha. This decrease in energy density of wastewater irrigated bermudagrass was associated with increased concentrations of K, Ca, and Na. After thermal conversion, these compounds are known to remain in the ash portion thereby decreasing the energy density. Nonetheless, the loss of energy density using treated effluent via SDI may be offset by the positive influence of these three elements for their catalytic properties in downstream thermal conversion processes such as promoting a lesser char yield and greater combustible gas formation.

Development of a second-generation environmentally superior technology for treatment of swine manure in the USA.

New swine waste management systems in North Carolina need to meet high performance standards of an environmentally superior technology (EST) regarding nitrogen, phosphorus, heavy metals, pathogens, ammonia and odor emissions, and remain affordable and simple to operate. The objective of this study was to develop a second-generation treatment system that can achieve high EST standards at reduced costs. The system used solids separation, nitrification/denitrification and phosphorus removal/disinfection, and was demonstrated at full-scale on a 5145-head swine farm during three production cycles (15-months). Removal efficiencies were: 98% suspended solids, 97% ammonia, 95% phosphorus, 99% copper and zinc, 99.9% odors, and 99.99% pathogens. The system met EST standards at 1/3 the cost of the previous version. Animal health and productivity were enhanced; hog sales increased 32,900 kg/cycle (5.6%). These results demonstrated that: (1) significant cost reductions were achieved by on-farm implementation and continued engineering improvements, and (2) the new waste management system substantially benefited livestock productivity.

Removal of phosphorus from livestock effluents.

For removal of phosphorus (P) from swine liquid manure before land application, we developed a treatment process that produces low P effluents and a valuable P by-product with minimal chemical addition and ammonia losses. The new wastewater process included two sequential steps: (i) biological nitrification and (ii) increasing the pH of the nitrified wastewater to precipitate P. We hypothesized that by reduction of inorganic buffers (NH(4)(+) and carbonate alkalinity) via nitrification, P could be selectively removed by subsequent hydrated lime [Ca(OH)(2)] addition. The objective of the study was to assess if this new treatment could consistently reduce inorganic buffer capacity with varied initial concentrations of N (100-723 mg NH(4)(+) L(-1)), P (26-85 mg TP L(-1)), and alkalinity (953-3063 mg CaCO(3) L(-1)), and then efficiently remove P from swine lagoon liquid. The process was tested with surface lagoon liquids from 10 typical swine farms in North Carolina. Each lagoon liquid received treatment in a nitrification bioreactor, followed by chemical treatment with Ca(OH)(2) at Ca rates of 0, 2, 4, 6, 8, 10, and 12 mmol L(-1) to precipitate P. This configuration was compared with a control that received the same Ca rates but without the nitrification pretreatment. The new process significantly reduced >90% the inorganic buffers concentrations compared with the control and prevented ammonia losses. Subsequent lime addition resulted in efficient pH increase to > or = 9.5 for optimum P precipitation in the nitrified liquid and significant reduction of effluent total P concentration versus the control. With this new process, the total P concentration in treated liquid effluent can be adjusted for on-farm use with up to >90% of P removal. The recovered solid Ca phosphate material can be easily exported from the farm and reused as P fertilizer. Therefore, the new process can be used to reduce the P content in livestock effluents to levels that would diminish problems of excess P accumulation in waste-amended soils.

Water quality improvements of wastewater from confined animal feeding operations after advanced treatment.

Current trends of animal production concentration and new regulations promote the need for environmentally safe alternatives to land application of liquid manure. These technologies must be able to substantially remove nutrients, heavy metals, and emissions of ammonia and odors and disinfect the effluent. A new treatment system was tested full-scale in a 4360-swine farm in North Carolina to demonstrate environmentally superior technology (EST) that could replace traditional anaerobic lagoon treatment. The system combined liquid-solids separation with nitrogen and phosphorus removal processes. Water quality was monitored at three sites: (i) the treatment plant as the raw manure liquid was depurated in the various processes, (ii) the converted lagoon as it was being cleaned up with the treated effluent, and (iii) an adjacent traditional anaerobic lagoon. The treatment plant removed 98% of total suspended solids (TSS), 76% of total solids (TS), 100% of 5-d biochemical oxygen demand (BOD(5)), 98% of total Kjeldahl nitrogen (TKN) and NH(4)-N, 95% of total phosphorus (TP), 99% of Zn, and 99% of Cu. The quality of the liquid in the converted lagoon improved rapidly as cleaner effluent from the plant replaced anaerobic lagoon liquid. The converted lagoon liquid became aerobic (dissolved oxygen, 6.95 mg L(-1); Eh, 342 mv) with the following mean reductions in the second year of the conversion: 73% of TSS, 40% of TS, 77% of BOD(5), 85% of TKN, 92% of NH(4)-N, 38% of TP, 37% of Zn, and 39% of Cu. These findings overall showed that EST can have significant positive impacts on the environment and on the livestock industries.

Denitrification of agricultural drainage line water via immobilized denitrification sludge.

Nonpoint source nitrogen is recognized as a significant water pollutant worldwide. One of the major contributors is agricultural drainage line water. A potential method of reducing this nitrogen discharge to water bodies is the use of immobilized denitrifying sludge (IDS). Our objectives were to (1) produce an effective IDS, (2) determine the IDS reaction kinetics in laboratory column bioreactors, and (3) test a field bioreactor for nitrogen removal from agricultural drainage line water. We developed a mixed liquor suspended solid (MLSS) denitrifying sludge using inoculant from an overland flow treatment system. It had a specific denitrification rate of 11.4 mg NO(3)-N g(-1) MLSS h(-1). We used polyvinyl alcohol (PVA) to immobilize this sludge and form IDS pellets. When placed in a 3.8-L column bioreactor, the IDS had a maximum removal rate (K(MAX)) of 3.64 mg NO(3)-N g(-1) pellet d(-1). In a field test with drainage water containing 7.8 mg NO(3)-N L(-1), 50% nitrogen removal was obtained with a 1 hr hydraulic retention time. Expressed as a 1 m(3) cubically-shaped bioreactor, the nitrogen removal rate would be 94 g NO(3)-N m(-2)d(-1), which is dramatically higher than treatment wetlands or passive carbonaceous bioreactors. IDS bioreactors offer potential for reducing nitrogen discharge from agricultural drainage lines. More research is needed to develop the bioreactors for agricultural use and to devise effective strategies for their implementation with other emerging technologies for improved water quality on both watershed and basin scales.

Development of environmentally superior treatment system to replace anaerobic swine lagoons in the USA.

A full-scale treatment system for swine manure was developed to eliminate discharge to surface and ground waters and contamination of soil and groundwater by nutrients and heavy metals, along with related release of ammonia, odor, and pathogens. The system greatly increased the efficiency of liquid-solid separation by polymer injection to increase solids flocculation. Nitrogen management to reduce ammonia emissions was accomplished by passing the liquid through a module where bacteria transformed ammonia into harmless nitrogen gas. Subsequent alkaline treatment of the wastewater in a phosphorus module precipitated phosphorus and killed pathogens. Treated wastewater was recycled to clean swine houses and for crop irrigation. The system was tested during one year in a 4400-head finishing farm as part of the Agreement between the Attorney General of North Carolina and swine producers Smithfield Foods, Premium Standard Farms and Frontline Farmers to replace traditional waste treatment anaerobic lagoons with environmentally superior technology. The on-farm system removed 97.6% of the suspended solids, 99.7% of BOD, 98.5% of TKN, 98.7% of soluble ammonia (NH(4)(+)-N), 95.0% of total P, 98.7% of copper and 99.0% of zinc. It also removed 97.9% of odor compounds in the liquid and reduced pathogen indicators to non-detectable levels. Based on performance obtained, it was determined that the treatment system met the Agreement's technical performance standards that define an environmentally superior technology. These findings overall showed that cleaner alternative technologies are technically and operationally feasible and that they can have significant positive impacts on the environment and the livestock industry.

Reduction of malodorous compounds from a treated swine anaerobic lagoon.

There is a need for treatment technologies that can eliminate environmental problems associated with anaerobic lagoons. These technologies must be able to capture nutrients, kill pathogens, and reduce emissions of ammonia and nuisance odors. To meet these needs, a full-scale wastewater treatment plant was installed as a demonstration project on one of three 4360-pig (Sus scrofa) production units in a finishing farm in Duplin County, North Carolina. Once the treatment plant was operational, flow of raw manure into the unit's corresponding lagoon was discontinued and the lagoon was used to store treated wastewater. Water quality was monitored in the converted lagoon and in the two conventional lagoons. A gas chromatographic method was developed to measure concentration of five selected malodorous compounds (phenol, p-cresol, 4-ethylphenol, indole, and skatole) in liquid lagoon samples. Dramatic improvements in the water quality parameters TKN, NH3-N, solids, COD, and BOD in the converted waste lagoon paralleled reductions in malodorous compounds. Nine months after conversion, identified malodorous compounds in liquid extractions averaged 6.6 and 38.8 ng mL(-1) in water from the converted lagoon and the conventional lagoons, respectively. The reduction was particularly marked for p-cresol, 4-ethylphenol, and skatole, all of which make important contributions to swine waste odors due to their characteristic odors and low detection thresholds.

Dewatering of phosphorus extracted from liquid swine waste.

Phosphorus (P) recovery from liquid swine manure is an attractive technology when on-farm application of liquid swine manure is not an option. We developed a technology that enables separation of this P, but its high moisture content makes transportation difficult. In this work, we investigated dewatering procedures to concentrate the P product. Sludge rich in calcium phosphate (> 20% P2O5) was obtained using a field prototype, and it was further dewatered using a combination of polymer treatment and filter bags. Anionic polyacrylamide polymer treatment (> or = 20 mg/L) was effective to flocculate the P-rich sludge, which enhanced filtration and dewatering. Without polymer, filtration was incomplete due to clogging of filters. Non-woven polypropylene and monofilament filter bag fabrics with mesh size < or = 200 microm retained > 99% of suspended solids and total P. Solids content dramatically increased from about 1.5% to > 90%. These dewatered solids can be transported more economically off the farm for use as a valuable fertilizer material.

Removal of pathogen and indicator microorganisms from liquid swine manure in multi-step biological and chemical treatment.

Concern has greatly increased about the potential for contamination of water, food, and air by pathogens present in manure. We evaluated pathogen reduction in liquid swine manure in a multi-stage treatment system where first the solids and liquid are separated with polymer, followed by biological nitrogen (N) removal using nitrification and denitrification, and then phosphorus (P) extraction through lime precipitation. Each step of the treatment system was analyzed for Salmonella and microbial indicators of fecal contamination (total coliforms, fecal coliforms, and enterococci). Before treatment, mean concentrations of Salmonella, total coliforms, fecal coliforms, and enterococci were 3.89, 6.79, 6.23 and 5.73 log(10) colony forming units (cfu)/ml, respectively. The flushed manure contained 10,590 mg/l TSS, 8270 mg/l COD, 688 mg/l TKN and 480 mg/l TP, which were reduced >98% by the treatment system. Results showed a consistent trend in reduction of pathogens and microbial indicators as a result of each step in the treatment system. Solid-liquid separation decreased their concentrations by 0.5-1 log(10). Additional biological N removal treatment with alternating anoxic and oxic conditions achieved a higher reduction with average removals of 2.4 log(10) for Salmonella and 4.1-4.5 log(10) for indicator microbes. Subsequent P treatment decreased concentration of Salmonella and pathogen indicators to undetectable level (<0.3 log(10) cfu/ml) due to elevated process pH (10.3). Our results indicate that nitrification/denitrification treatment after solids separation is very effective in reducing pathogens in liquid swine manure and that the phosphorus removal step via alkaline calcium precipitation produces a sanitized effluent which may be important for biosecurity reasons.