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.     

Development of environmentally superior technologies in the US and policy

“Environmentally superior technology” (EST) represents a research initiative in North Carolina (NC) to develop alternatives to lagoon treatment and land application of swine manure. EST performance standards included impacts of animal waste to surface and groundwater, emission of ammonia and odor, release of disease-transmitting pathogens, and heavy metal contamination of soil and groundwater. Five technologies were shown to meet these standards: a solids separation/nitrification–denitrification/soluble phosphorus removal system; a thermophilic anaerobic digester system; a centralized composting system; a gasification system; and a fluidized bed combustion system. Economic data compiled for all EST showed annualized (10-year) costs of retrofitting existing swine farms with the technologies ranged between $90 and over $400 per 1000 lbs. steady state live-weight. Value-engineering to reduce the costs of targeted EST has been successful. Policy providing institutional incentives to incorporate EST has been enacted as a result of this study.     

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.     

Improvement in post-treatment of digested swine wastewater

The performance of sequencing batch reactor (SBR) during post-treatment of digested effluent of swine wastewater was investigated. While operating SBR to treat the digested effluent directly, the performance was very poor with COD removal rate about 10%, and NH4+-N removal rate nearly 50%, with a scarce removal of total phosphorus. The performance apparently improved after adding raw swine wastewater or alkali to digested effluent. Although similar results for NH4+-N removal were achieved adopting both measures, the addition of raw wastewater proved superior in removing total nitrogen and total phosphorus. The addition of raw wastewater obtained effluent COD around 300 mg/L which was lower than that after alkali addition i.e. around 550 mg/L. Judged from the investment, oxygen demand, sludge yield, biogas production and running cost, the traditional combined anaerobic-SBR process is unfeasible to treat swine wastewater, while the combined anaerobic-SBR process with addition of raw swine wastewater can be a suitable biotechnology.     

Product and Economic Analysis of Direct Liquefaction of Swine Manure

Direct hydrothermal liquefaction of biomass is a technology that has shown promising results in treating waste and producing oil. A batch hydrothermal liquefaction system was used to treat swine manure, and it successfully converted up to 70% of swine manure volatile solids into oil and reduced manure chemical oxygen demand by up to 75% (He et al., Trans ASAE 43(6):1827?C1833, 2000). A continuous-flow reactor was developed and resulted in similar conversion rates to the batch process, indicating the potential for scale-up (Ocfemia, 2005). This study investigates the hydrothermal process in relation to a livestock system to determine the impact on oil yields and fertilizer values that might be realized in a farm-scale application. Oil products from the hydrothermal process are maximized using manure containing around 20% solids, but typical swine confinement facilities contain wetter manure slurries. A preliminary investigation of liquid?Csolid separation methods was conducted to determine the resultant oil yields and the effects of the hydrothermal process on fertilizer values in the wastewater as compared to the unprocessed manure. Energy and economic analyses of the liquid?Csolid separation and hydrothermal liquefaction processes were also conducted. The hydrothermal process results in an oil product as well as a fertilizer product that retains the majority of its nitrogen value with a reduced level of phosphorus (as compared to the unprocessed swine manure). The economic analyses indicate feasibility for several different liquid?Csolid separation methods, dependent on the equipment and maintenance costs assumed for each method. Conveyor-belt manure collection systems in conjunction with hydrothermal liquefaction are especially promising.     

Characteristics of solids, BOD5 and VFAs in liquid swine manure treated by short-term low-intensity aeration for long-term storage

A laboratory-scale experiment presents data that reveal the temporal characteristics of solids, biochemical oxygen demand (BOD5) and volatile fatty acids (VFAs) in the aerated liquid swine manure for minimizing odor generation potential during 190-day storage. The performance of 15-day aeration of liquid manure with initial total solids (TS) content from 0.5% to 4.0% was examined at low-intensity aeration rates, i.e., +35 mV oxidation-reduction potential (ORP), 1.0 mg O2/l and 3.0 mg O2/l dissolved oxygen (DO). Odor generation potential was evaluated using VFAs. The aeration process contributed remarkably to the decomposition of TS, total volatile solids (TVS), BOD5 and VFAs. Moreover, the stabilization of manure due to aeration could last up to 190 days. The TS reduction on day 190 ranging from 6.3% to 32.7%, 20.2% to 39.1%, 19.0% to 41.0% were realized under the intensities of +35 mV ORP, 1.0 and 3.0 mg O2/l, respectively. At the same time, the reduction of BOD5 and VFAs reached around 7.8% to 69.5%, 17.2% to 79.9% and 21.9% to 91.1%; 0.4% to 91.0%, 60.4% to 95.0% and 70.4% to 94.1%. The liquid manure with low solids (e.g., TS of 0.5% and 1.0%) offered an advantageous condition for aeration treatment, particularly for biodegradation of BOD5 and VFAs. The odor generation potential could also be evaluated by the levels of solids and BOD5 in the manure. Increasing aeration intensity would significantly diminish the odor generation potential for given levels of solids and/or BOD5. Fifteen-day aeration with intensity of 1.0 mg O2/l may be recommended at farm level for both odor control and energy savings.     

Carvacrol and Thymol Reduce Swine Waste Odor and Pathogens: Stability of Oils

An incomplete anoxic fermentation of livestock waste results in offensive odor emissions. Antimicrobial additives may be useful in controlling odor emissions and pathogens. Natural antimicrobial compounds, carvacrol or thymol at 16.75 mM (2.5 g/l) completely inhibited the production of the offensive odor compounds, isobutyrate, valerate, isovalerate, and cresol, and significantly reduced other short-chain volatile fatty acids and gas emissions from swine waste. Fecal coliforms were reduced from 6.3 × 10⁶ to 1.0 × 10³ cells per ml 2 days after treatment with carvacrol (13.3 mM) and were not detectable within 14 days. Total culturable anaerobic bacteria were reduced from 12.4 × 10¹⁰ to 7.2 × 10⁸ cells per ml after 2 days and were suppressed below this level for 28 days. Lactate production was not prevalent in untreated swine waste indicating that the microbial populations differ from those in cattle waste. Carvacrol and thymol were stable in swine waste under anoxic conditions for 62 days with 90 to 95% of the additive being recovered in the waste solids. In conclusion, carvacrol and thymol are not metabolized in anoxic swine waste and they are potentially useful in controlling odor emissions and pathogens in swine waste. Received: 22 March 2001 / Accepted: 14 May 2001     

Anaerobic Co-digestion of Swine Manure and Microalgae <Emphasis Type="Italic">Chlorella</Emphasis> sp.: Experimental Studies and Energy Analysis

Integration of algae production with livestock waste management has the potential to recover energy and nutrients from animal manure, while reducing discharges of organic matter, pathogens, and nutrients to the environment. In this study, microalgae Chlorella sp. were grown on centrate from anaerobically digested swine manure. The algae were harvested for mesophilic anaerobic digestion (AD) with swine manure for bioenergy production. Low biogas yields were observed in batch AD studies with algae alone, or when algae were co-digested with swine manure at ≥43 % algae (based on volatile solids [VS]). However, co-digestion of 6–16 % algae with swine manure produced similar biogas yields as digestion of swine manure alone. An average methane yield of 190 mL/g VS_fed was achieved in long-term semi-continuous co-digestion studies with 10?±?3 % algae with swine manure. Data from the experimental studies were used in an energy analysis assuming the process was scaled up to a concentrated animal feeding operation (CAFO) with 7000 pigs with integrated algae-based treatment of centrate and co-digestion of manure and the harvested algae. The average net energy production for the system was estimated at 1027 kWh per day. A mass balance indicated that 58 % of nitrogen (N) and 98 % of phosphorus (P) in the system were removed in the biosolids. A major advantage of the proposed process is the reduction in nutrient discharges compared with AD of swine waste without algae production.     

猪场恶臭的生物技术综合处理

集约化猪场恶臭的生物处理可以在饲养的营养技术、饲养过程和粪便处理阶段分别处理,试验表明使用含有微生物制剂等成分的除臭剂为饲料添加剂,可使猪舍氨气和硫化氧分别降低38．6％和20．6％,调节池中氨气和硫化氧分别降低14．7％和20．4％,臭气浓度降低43.8％。而在猪舍和饲养过程中使用恶臭吸附剂直接放置于猪场环境中,可降低猪舍中的氨气和硫化氢浓度29．5％和30．4％,降低调节池中的氨气和硫化氢30．2％和0％,降低臭气浓度31．9％。在猪场污水处胛阶段使用雾化除臭处理设备,可以降低调节池、贮粪池和水力筛池的氨气浓度14．7％、24．6％和48.2％,分别降低硫化氢浓度18．1％、25．8％和13．0％,同时降低猪场臭气浓度82．6％。     

Aerobic treatment of dairy wastewater with sequencing batch reactor systems

Performances of single-stage and two-stage sequencing batch reactor (SBR) systems were investigated for treating dairy wastewater. A single-stage SBR system was tested with 10,000 mg/l chemical oxygen demand (COD) influent at three hydraulic retention times (HRTs) of 1, 2, and 3 days and 20,000 mg/l COD influent at four HRTs of 1, 2, 3, and 4 days. A 1-day HRT was found sufficient for treating 10,000-mg/l COD wastewater, with the removal efficiency of 80.2% COD, 63.4% total solids, 66.2% volatile solids, 75% total Kjeldahl nitrogen, and 38.3% total nitrogen from the liquid effluent. Two-day HRT was believed sufficient for treating 20,000-mg/l COD dairy wastewater if complete ammonia oxidation is not desired. However, 4-day HRT needs to be used for achieving complete ammonia oxidation. A two-stage system consisting of an SBR and a complete-mix biofilm reactor was capable of achieving complete ammonia oxidation and comparable carbon, solids, and nitrogen removal while using at least 1/3 less HRT as compared to the single SBR system.     

Solids and nutrients removals from the liquid fraction of swine slurry through screening and flocculation treatment and influence of these processes on anaerobic biodegradability

A correct separation of solids from liquid fraction is crucial for a successful treatment of swine manure. For this reason an in-depth study of flocculant addition on different livestock wastewaters was carried out. Two flushed swine manure matrices, namely the mixture from nursery and feeder-to-finish pigs and the feeder-to-finish slurry alone, were tested for solids and nutrients removals from liquid fractions. The separation techniques applied were sieving and flocculation. A range of 80-200 ppm of polyacrylamide (PAM) followed by screening was employed in the case of flocculation treatment. The best results were observed when using the highest PAM dose in the matrix correspondent to the mixture of slurries. The removal rates in the liquid fraction were 73% for total solids, 87% for volatile solids, 98% for suspended total and volatile solids, 71% for chemical oxygen demand, 40% for total Kjeldahl nitrogen, and 34% for soluble phosphorus. Once the best PAM dose (120 ppm) was chosen, an anaerobic biodegradability study was performed in order to check the increase of methane production in the separated fractions by using the flocculant and the screen. The assay determined that the solid fractions biodegradability was constant at 79%. Meanwhile for the liquid fractions, an increase of 9% points was achieved with PAM-amendment when compared with 82% reached for the liquid fraction obtained by screening.     

Efficiency of ammonia and phosphorus removal from a colombian agroindustrial wastewater by the microalgae Chlorella vulgaris and Scenedesmus dimorphus

The ammonia and phosphorus removal efficiencies of the microalgae Chlorella vulgaris and Scenedesmus dimorphus, during biotreatment of secondary effluent from an agroindustrial wastewater of a dairy industry and pig farming, were evaluated. The microalgae were isolated from a wastewater stabilization pond near Santafé de Bogotá, Colombia. Batch cultures were made using both species in 4-1 cylindrical glass bioreactors each containing 2l of culture. Chlorella vulgaris was also cultivated on wastewater in a triangular bioreactor. Three 216-h experimental cycles were run for each microalga and in each bioreactor. In the cylindrical bioreactor, S. dimorphus was more efficient in removing ammonia than C. vulgaris. However, the final efficiency of both microalgae at the end of each cycle was similar. Both microalgae removed phosphorus from the wastewater to the same extent in a cylindrical bioreactor. Using C. vulgaris, the triangular bioreactor was superior for removing ammonia and the cylindrical bioreactor was superior for removing phosphorus. This study shows the potential of using these microalgae to reduce the environmental pollution of heavily contaminated agroindustrial waters currently disposed of untreated into the waterways and streams of tropical Colombia.     

Performance study of vegetated sequencing batch coal slag bed treating domestic wastewater in suburban area

A practical and affordable wastewater treatment system serving small community in suburban areas was studied. The system was a vegetated sequencing batch coal slag bed integrated with the rhythmical movement of wastewater and air like that of a sequencing batch reactor. The removal mechanisms capitalized on the pollutant removal process in conventional constructed wetland. Cyperus alternifolius was planted into the coal slag bed to form a novel plant-soil-microbial interactive system. Nutrients in the domestic wastewater, which cause environmental nuisance like eutrophication, were targeted to be eliminated by the process design. Operated with the contact time of 18 h, the treatment systems achieved around 60% removal efficiency for carbonaceous matters. The removals of ammonia nitrogen and phosphorus were about 50% and 40%, respectively, while the removal of total suspended solids was approaching 80%. From the current study, the construction cost of the vegetated sequencing batch coal slag bed was 256 RMB/m3 and the operation cost was 0.13 RMB/m3. With the advantages of ease of operation, low costs, desirable treatment efficiency and aesthetic value, the vegetated sequencing batch coal slag bed is proposed to be an alternative for onsite domestic wastewater treatment in suburban areas.     

Using agar–alginate immobilized cyanobacteria (Dermocarpella sp.) arranged in tubular chains to treat swine farm waste water

Livestock wastewater that is discharged into rivers and ponds results in eutrophication, which would then cause an increase in microorganisms, microalgae, and macrophytes. The derivatives of which critically damage aquatic life and agricultural irrigation. This study designed a swine farm wastewater bioremediation system, by using tubular chained cyanobacteria-immobilized agar–alginate blocks and cyanobacteria biological absorption to reduce wastewater pollution. Swine farm wastewater was filtered through a long tube stuffed with cyanobacteria (Dermocarpella sp.)-immobilized agar–alginate blocks. The removal efficiencies of biological oxygen demand, chemical oxygen demand, phosphorous, ammonia, and suspension solids were evaluated.     

Foaming control by automatic carbon source adjustment using an ORP profile in sequencing batch reactors for enhanced nitrogen removal in swine wastewater treatment

Incomplete denitrification and ammonia accumulation were found to cause proliferation of filamentous microorganisms in sequencing batch reactors (SBRs) for swine wastewater treatment. Foaming was observed in response to the accumulation of 115.2 and 12.2 mg/L of nitrate and ammonia, respectively. The mixed liquor suspended solids (MLSS) level in SBRs was decreased to 2,000 mg/L and the suspended solids in the effluent reached 200 mg/L when foaming appeared. However, the use of swine waste as an external carbon source for enhanced biological nitrogen removal was found to effectively control the foaming caused by filamentous microorganisms. Therefore, an optimum strategy for the addition of swine waste was designed using integrated real-time control to provide pulse input control of slurry based on the “nitrate knee” in the oxidation–reduction potential profile. In this case, the MLSS concentration was maintained at an average value of approximately 7,550 mg/L, while the SS in the effluent was less than 30 mg/L.     

Biotreatment of heavy oil wastewater by combined upflow anaerobic sludge blanket and immobilized biological aerated filter in a pilot-scale test

A field pilot study has been constructed in the Liaohe oilfield, China to treat heavy oil wastewater with large amounts of dissolved recalcitrant organic compounds and low nutrient of nitrogen and phosphorus by an upflow anaerobic sludge blanket (UASB) coupled with immobilized biological aerated filters (I-BAFs). By operating the system for 252 days (including the start-up of 128 days), the chemical oxygen demand (COD), ammonia nitrogen (NH₃-N) and suspended solid (SS) in the wastewater were removed by 74%, 94% and 98%, respectively. GC–MS analysis indicated that most of alkanes were degraded by the UASB process, while the I-BAF played important roles both in degrading organic compounds and in removing the NH₃-N and SS. The bacterial community structural analysis based on the PCR-DGGE technology reveals that the predominant bacteria in the UASB reactor belong to the Bacillales and Rhodobacterales, and that in the I-BAF was identified as uncultured soil bacterium. Our results suggest that the combined biotreatment system has immense potential in large-scale treatment of heavy oil wastewater.     

SELCO-Ecopurin pig slurry treatment system

As the practice of intensive animal production increases, there is a need for affordable treatment technologies that can help manage the large amounts of manure generated. Our approach has been to develop an efficient liquid-solid separation module using polymer technology and integrate this separation module into systems of treatment technologies for both the separated liquid and solids. We describe the progress that has been made in management techniques and new technological alternatives for manure treatment and generation of value added by-products based on the SELCO-Ecopurin separation technology and experiences during the last five years in 12 livestock farms in Spain, Italy and the USA. High recovery of solids (>90%) makes the use of advanced purification of the liquid a more economical alternative. The liquid can be further treated to reduce N and P and produce effluents virtually free of these nutrients. Production of methane and energy was affected by solids concentration; the anaerobic process was optimised with polymer application rate of 120 ppm during separation and a solids content of 13%.     

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.     

Effect of carbon to nitrogen (C:N) ratio on nitrogen removal from shrimp production waste water using sequencing batch reactor

The United States Marine Shrimp Farming Program (USMSFP) introduced a new technology for shrimp farming called recirculating raceway system. This is a zero-water exchange system capable of producing high-density shrimp yields. However, this system produces wastewater characterized by high levels of ammonia, nitrite, and nitrate due to 40% protein diet for the shrimp at a high density of 1,000 shrimp per square meter. The high concentrations of nitrate and nitrite (greater than 25 ppm) are toxic to shrimp and cause high mortality. So treatment of this wastewater is imperative in order to make shrimp farming viable. One simple method of treating high-nitrogen wastewater is the use of a sequencing batch reactor (SBR). An SBR is a variation of the activated sludge process, which accomplishes many treatment events in a single reactor. Removal of ammonia and nitrate involved nitrification and denitrification reactions by operating the SBR aerobically and anaerobically in sequence. Initial SBR operation successfully removed ammonia, but nitrate concentrations were too high because of carbon limitation in the shrimp production wastewater. An optimization study revealed the optimum carbon to nitrogen (C:N) ratio of 10:1 for successful removal of all nitrogen species from the wastewater. The SBR operated with a C:N ratio of 10:1 with the addition of molasses as carbon source successfully removed 99% of ammonia, nitrate, and nitrite from the shrimp aquaculture wastewater within 9 days of operation.     

Performance of subsurface flow constructed wetland taking pretreated swine effluent under heavy loads

Subsurface flow constructed wetlands (SSFCW) subjected to changing of loading rates are poorly understood, especially when used to treat swine waste under heavy loads. This study employed a SSFCW system to take pretreated swine effluent at three hydraulic retention times (HRT): 8.5-day HRT (Phase I), 4.3-day HRT (Phase II), and 14.7-day HRT (Phase III). Results showed that the system responded well to the changing hydraulic loads in removing suspended solids (SS) and carbonaceous oxygen demands. The averaged reduction efficiencies for four major constituents in the three phases were: SS 96-99%, chemical oxygen demand (COD) 77-84%, total phosphorus 47-59%, and total nitrogen (TN) 10-24%. While physical mechanisms were dominant in removing pollutants, the contributions of microbial mechanisms increased with the duration of wetland use, achieving 48% of COD removed and 16% of TN removed in the last phase. Water hyacinth made only a minimal contribution to the removal of nutrients. This study suggested that the effluent from SSFCW was appropriate for further treatment in land applications for nutrient assimilation.