The fate of crop nutrients during digestion of swine manure in psychrophilic anaerobic sequencing batch reactors

The objectives of the study were to measure the levels of manure nutrients retained in psychrophilic anaerobic sequencing batch reactors (PASBRs) digesting swine manure, and to determine the distribution of nutrients in the sludge and supernatant zones of settled bioreactor effluent. Anaerobic digestion reduced the total solids (TS) concentration and the soluble chemical oxygen demand (SCOD) of manure by 71.4% and 79.9%, respectively. The nitrogen, potassium, and sodium fed with the manure to the PASBRs were recovered in the effluent. The bioreactors retained on average 25.5% of the P, 8.7% of the Ca, 41.5% of the Cu, 18.4% of the Zn, and 67.7% of the S fed to the PASBRs. The natural settling of bioreactor effluent allowed further nutrient separation. The supernatant fraction, which represented 71.4% of effluent volume, contained 61.8% of the total N, 67.1% of the NH4-N, and 73.3% of the Na. The settled sludge fraction, which represented 28.6% of the volume, contained 57.6% of the solids, 62.3% of the P, 71.6% of the Ca, 89.6% of the Mg, 76.1% of the Al, 90.0% of the Cu, 74.2% of the Zn, and 52.2% of the S. The N/P ratio was increased from 3.9 in the raw manure to 5.2 in the bioreactor effluent and 9.2 in the supernatant fraction of the settled effluent. The PASBR technology will then substantially decrease the manure management costs of swine operations producing excess phosphorus, by reducing the volume of manure to export outside the farm. The separation of nutrients will also allow land spreading strategies that increase the agronomic value of manure by matching more closely the crop nutrient requirements.     

Evolution of microorganisms in thermophilic-dry anaerobic digestion

Microbial population dynamics were studied during the start-up and stabilization periods in thermophilic-dry anaerobic digestion at lab-scale. The experimental protocol was defined to quantify Eubacteria and Archaea using Fluorescent in situ hybridization (FISH) in a continuously stirred tank reactor (CSTR), without recycling solids. The reactor was subjected to a programme of steady-state operation over a range of the retention times from 40 to 25 days, with an organic loading rate between 4.42 and 7.50 kg volatile solid/m3/day. Changes in microbial concentrations were linked to traditional performance parameters such as biogas production and VS removal. The relations of Eubacteria:Archaea and H2-utilising methanogens:acetate-utilising methanogens were 88:12 and 11:1, respectively, during start-up stage. Hydrogenotrophic methanogens, although important in the initial phase of the reactor start-up, were displaced by acetoclastic methanogens at steady-state, thus their relation were 7:32, respectively. The methane yield coefficient, the methane content in the biogas and VS removal were stabilized around 0.30 LCH4/gCOD, 50% and 80%, respectively. Methanogenic population correlated well with performance measurements.     

UV inactivation of pathogenic and indicator microorganisms

Survival was measured as a function of the dose of germicidal UV light for the bacteria Escherichia coli, Salmonella typhi, Shigella sonnei, Streptococcus faecalis, Staphylococcus aureus, and Bacillus subtilis spores, the enteric viruses poliovirus type 1 and simian rotavirus SA11, the cysts of the protozoan Acanthamoeba castellanii, as well as for total coliforms and standard plate count microorganisms from secondary effluent. The doses of UV light necessary for a 99.9% inactivation of the cultured vegetative bacteria, total coliforms, and standard plate count microorganisms were comparable. However, the viruses, the bacterial spores, and the amoebic cysts required about 3 to 4 times, 9 times, and 15 times, respectively, the dose required for E. coli. These ratios covered a narrower relative dose range than that previously reported for chlorine disinfection of E. coli, viruses, spores, and cysts.     

Pathogen removal in farm-scale psychrophilic anaerobic digesters processing swine manure

This study assessed the efficiency of commercial-scale psychrophilic anaerobic digestion in sequencing batch reactors (PADSBRs) for pathogen removal from pig manure. The impact of treatment cycle length and of hydraulic flow regimes on pathogen removal efficiency was investigated. Two conventionally operated SBRs (BR1 and BR2) and two SBRs simultaneously fed during the draw step (BR3 and BR4) were monitored over a two-year period. PADSBRs significantly decreased the concentration of coliforms, Salmonella, Campylobacter spp., and Y. enterocolitica, respectively from about 10⁶, 10³ CFU g⁻¹, 10³, and 10⁴ CFU g⁻¹ to undetectable levels in most samples. Densities of the gram-positive Clostridium perfringens and Enterococcus spp. remained high (10⁵ CFU g⁻¹) in the digesters throughout treatment. The PADSBRs maintained the same level of pathogen removal when the treatment cycle length was reduced from 2 to 1 week. Mass balances on volatile fatty acids (VFAs) revealed short-circuits of inlet flow respectively averaging 6.3% and 6.4% for BR3 and BR4, significantly reducing the overall performance of these reactors regarding pathogens removal. The results obtained in this study show the ability of low temperature anaerobic digestion to remove or significantly reduce indicator and pathogen concentration from raw pig manure.     

UV inactivation of pathogenic and indicator microorganisms.

Survival was measured as a function of the dose of germicidal UV light for the bacteria Escherichia coli, Salmonella typhi, Shigella sonnei, Streptococcus faecalis, Staphylococcus aureus, and Bacillus subtilis spores, the enteric viruses poliovirus type 1 and simian rotavirus SA11, the cysts of the protozoan Acanthamoeba castellanii, as well as for total coliforms and standard plate count microorganisms from secondary effluent. The doses of UV light necessary for a 99.9% inactivation of the cultured vegetative bacteria, total coliforms, and standard plate count microorganisms were comparable. However, the viruses, the bacterial spores, and the amoebic cysts required about 3 to 4 times, 9 times, and 15 times, respectively, the dose required for E. coli. These ratios covered a narrower relative dose range than that previously reported for chlorine disinfection of E. coli, viruses, spores, and cysts.     

Regiospecific dechlorination of pentachlorophenol by dichlorophenol-adapted microorganisms in freshwater, anaerobic sediment slurries.

The reductive dechlorination of pentachlorophenol (PCP) was investigated in anaerobic sediments that contained nonadapted or 2,4- or 3,4-dichlorophenol (DCP)-adapted microbial communities. Adaptation of sediment communities increased the rate of conversion of 2,4- or 3,4-DCP to monochlorophenols (CPs) and eliminated the lag phase before dechlorination was observed. Both 2,4- and 3,4-DCP-adapted sediment communities dechlorinated the six DCP isomers to CPs. The specificity of chlorine removal from the DCP isomers indicated a preference for ortho-chlorine removal by 2,4-DCP-adapted sediment communities and for para-chlorine removal by 3,4-DCP-adapted sediment communities. Sediment slurries containing nonadapted microbial communities either did not dechlorinate PCP or did so following a lag phase of at least 40 days. Sediment communities adapted to dechlorinate 2,4- or 3,4-DCP dechlorinated PCP without an initial lag phase. The 2,4-DCP-adapted communities initially removed the ortho-chlorine from PCP, whereas the 3,4-DCP-adapted communities initially removed the para-chlorine from PCP. A 1:1 mixture of the adapted sediment communities also dechlorinated PCP without a lag phase. Dechlorination by the mixture was regiospecific, following a para greater than ortho greater than meta order of chlorine removal. Intermediate products of degradation, 2,3,5,6-tetrachlorophenol, 2,3,5-trichlorophenol, 3,5-DCP, 3-CP, and phenol, were identified by a combination of cochromatography (high-pressure liquid chromatography) with standards and gas chromatography-mass spectrometry.     

Immobilization of anaerobic bacteria on rubberized-coir for psychrophilic digestion of night soil

Low-ambient temperatures, <30 degrees C, are known to cause drastic reduction in the efficiency of anaerobic biodigesters due to low-growth rate of the constituent bacterial consortium. Immobilization of anaerobic bacteria has been attempted in the biodigester operating at 10 degrees C. Various matrices were screened and evaluated for the immobilization of bacteria in digesters. Anaerobic digestion of night soil was carried out with hydraulic retention time in the range of 9-18 days. Among the tested matrices, rubberized-coir was found to be the most useful at 10 degrees C with optimum hydraulic retention time of 15 days. Optimum amount of coir was found as 25 g/L of the working volume of biodigesters. Immobilization of bacteria on the coir was observed by scanning electron microscopy and fluorescent microscopy. The study indicates that rubberized-coir can be utilized to increase biodegradation of night soil at higher organic loading. Another advantage of using this matrix is that it is renewable and easily available in comparison to other synthetic polymeric matrices.     

Psychrophilic anaerobic digestion biotechnology for swine mortality disposal

The objective of this study was to investigate the feasibility of using psychrophilic anaerobic digestion in sequencing batch reactors (PADSBRs) to co-digest grinded swine carcasses and swine manure slurry at 20 degrees C and 25 degrees C. The PADSBRs were operated on two-week and four-week treatment cycle lengths, which included the fill, react, and draw phases. Two carcass loading rates (CLRs) were tested, that is 20 and 40g of carcass per litre of manure, which were equivalent to 4 and 8 times, respectively, the normal mortality rate on commercial farms. The PADSBR performance was compared to that of PADSBRs operated at 25 degrees C and fed manure only. The addition of swine carcass to PADSBR feed did not affect the stability of the bioreactors at both CLRs. The performance of the PADSBRs co-digesting swine carcasses was not statistically different from the control in terms of biogas production and quality. There was no accumulation of volatile fatty acids in the bioreactors at the end of the treatment cycle. The mixed-liquor pH and alkalinity remained within acceptable ranges for the anaerobic microflora. Also, there was no operational problem caused by the formation of foam and scum in the system.     

Simulation of low temperature anaerobic digestion of dairy and swine manure

The data reported by L.M. Safley, P.W. Westerman [Bioresource Technology 47 (2) (1994) 165-171] from the laboratory digestion of dairy and swine manure at psychrophilic temperatures (i.e., 10-23 degrees C) have been used to determine the response of the latest comprehensive dynamic mathematical model of methanogenesis [D.T. Hill, S.A. Cobb, Transactions of the ASAE 39 (2) (1996) 565-573] in this low temperature range. Extensive performance data from digesters using animal waste in this temperature range have been lacking, thus allowing limited validation of the comprehensive model. The results of the comprehensive model simulations were compared with the actual data reported by Safley and Westerman (loc. cit.) and with their empirical regression models. Results indicate that the comprehensive model is as accurate as Safley and Westerman's models for three of the four cases reported, but shows a great dissimilarity for the fourth case.     

Metabolic activity of pathogenic bacteria during semicontinuous anaerobic digestion.

In natural environments such as anaerobic digesters, bacteria are frequently subjected to the stress of nutrient fluxes because of the continual changes in the flow of nutrients, and to survive, they must be capable of adapting readily to nutrient changes. In this study, the metabolic activities of Escherichia coli, Salmonella typhimurium, Yersinia enterocolitica, Listeria monocytogenes, and Campylobacter jejuni were studied within culture bags (Versapor-200 filters, 0.22-microns pore size) in laboratory anaerobic digesters. The metabolic activity of these bacteria was indicated by their adenylate energy charge (EC) ratios and their ability to incorporate [3H]thymidine, which was related to the respective changes in viable numbers within the culture bags during anaerobic digestion. Fluctuations in the adenylate EC ratios, the uptake of [3H]thymidine, and the viable numbers of E. coli, S. typhimurium, Y. enterocolitica, and L. monocytogenes cells were probably due to constant changes in the amount of available nutrients within the anaerobic digesters. The viability of S. typhimurium increased quickly after a fresh supply of nutrients was added to the system as indicated by the uptake of [3H]thymidine and an increase in the adenylate EC ratios. The viable numbers of E. coli, S. typhimurium, Y. enterocolitica, and L. monocytogenes organisms declined rapidly from 10(7) to 10(8) CFU/ml to 10(3) to 10(4) CFU/ml and remained at this level for an indefinite period. The decimal reduction time calculated during the period of exponential decline ranged from 0.8 to 1.2 days for these bacteria. C. jejuni had the greatest mean decimal reduction time value (3.6 days).(ABSTRACT TRUNCATED AT 250 WORDS)     

The effect of temperature fluctuations on psychrophilic anaerobic sequencing batch reactors treating swine manure

Under northern climatic conditions, a temporary decrease in the temperature of anaerobic reactors treating swine manure is likely to happen at the farm. The objective of this study was to evaluate the impact of temperature fluctuations, between 10 and 20 degrees C, on the stability and performance of psychrophilic anaerobic sequencing batch reactors (ASBRs) treating swine manure. Methane yield decreased from 0.266+/-0.014 l/g of total chemical oxygen demand (TCOD) fed to the ASBRs at 20 degrees C to 0.218+/-0.022 and 0.080+/-0.002 l/g TCOD (fed) at 15 and 10 degrees C, respectively. Soluble chemical oxygen demand (SCOD) reduction decreased from 94.2+/-1.1% at 20 degrees C to 78.8+/-3.0% at 15 degrees C and 60.4+/-6.4% at 10 degrees C. Total COD removal also tended to decrease as temperature was lowered, but difference between operating temperatures was not as pronounced. A lower methanogenic activity in the ASBRs operated at 10 degrees C probably favoured quiescent conditions during the settling period, thereby increasing physical removal of the TCOD through sedimentation of the solids with the biomass. When the operating temperature was increased back to 15 and 20 degrees C, methane yield and SCOD reduction improved, but reactor performance remained significantly (P<0.05) lower than that achieved before the cycles at 10 degrees C. Results from this experiment nevertheless suggested that fluctuation in the operating temperature of psychrophilic ASBRs should only have temporary effects on the performance and stability of the process.     

Survival of pathogenic bacteria during mesophilic anaerobic digestion of animal waste

The survival of pathogenic bacteria was investigated during the operation of a full-scale anaerobic digester which was fed daily and operated at 28°C. The digester had a mean hydraulic retention time of 24 d. The viable numbers of Escherichia coli, Salmonella typhimurium, Yersinia enterocolitica, Listeria monocytogenes and Campylobacter jejuni were reduced during mesophilic anaerobic digestion. Echerichia coli had the smallest mean viable numbers at each stage of the digestion process. Its mean T₉₀ value was 76.9 d. Yersinia enterocolitica was the least resistant to the anaerobic digester environment; its mean T₉₀ value was 18.2 d. Campylobacter jejuni was the most resistant bacterium; its mean T₉₀ value was 438.6 d. Regression analysis showed that there were no direct relationships between the slurry input and performance of the digester and the decline of pathogen numbers during the 140 d experimental period.     

Ecophysiology of psychrophilic and psychrotolerant microorganisms.

This review describes psychrophilic and psychrotolerant microorganisms, which are abundant in different kinds of environments. Their ecophysiological properties and strategies for survival are reviewed in relation to their occurrences in marine and terrestrial environments, with special reference to the deep-sea, the sea ice and the permafrost soils.     

Reduction of 17-keto steroids by anaerobic microorganisms isolated from human fecal flora

The 17-keto function of phenolic steroids is reduced by the following intestinal bacteria: Eubacterium lentum, Clostridium paraputrificum, Clostridium J-1 and Clostridium innocuum. The 17-keto group of androstenedione is reduced solely by Bacteroides fragilis.     

The effect of slurry storage and anaerobic digestion on survival of pathogenic bacteria

The decline in viable numbers of Salmonella typhimurium, Yersinia enterocolitica and Listeria monocytogenes in beef cattle slurry is temperature-dependent; they decline more rapidly at 17°C than at 4°C. Mesophilic anaerobic digestion caused an initial rapid decline in the viable numbers of Escherichia coli, Salm. typhimurium, Y. enterocolitica and L. monocytogenes. This was followed by a period in which the viable numbers were not reduced by 90%. The T₉₀ values of E. coli, Salm. typhimurium and Y. enterocolitica ranged from 0.7 to 0.9 d during batch digestion and 1.1 to 2.5 d during semi-continuous digestion. Listeria monocytogenes had a significantly higher mean T₉₀ value during semi-continuous digestion (35.7 d) than batch digestion (12.3 d). Anaerobic digestion had little effect in reducing the viable numbers of Campylobacter jejuni.     

Challenge of psychrophilic anaerobic wastewater treatment

Psychrophilic anaerobic treatment is an attractive option for wastewaters that are discharged at moderate to low temperature. The expanded granular sludge bed (EGSB) reactor has been shown to be a feasible system for anaerobic treatment of mainly soluble and pre-acidified wastewater at temperatures of 5--10 degrees C. An organic loading rate (OLR) of 10--12 kg chemical oxygen demand (COD) per cubic meter reactor per day can be achieved at 10--12 degrees C with a removal efficiency of 90%. Further improvement might be obtained by a two-module system in series. Stabile methanogenesis was observed at temperatures as low as 4--5 degrees C. The specific activity of the mesophilic granular sludge was improved under psychrophilic conditions, which indicates that there was growth and enrichment of methanogens and acetogens in the anaerobic system. Anaerobic sewage treatment is a real challenge in moderate climates because sewage belongs to the 'complex' wastewater category and contains a high fraction of particulate COD. A two-step system consisting of either an anaerobic up-flow sludge bed (UASB) reactor combined with an EGSB reactor or an anaerobic filter (AF) combined with an anaerobic hybrid reactor (AH) is successful for anaerobic treatment of sewage at 13 degrees C with a total COD removal efficiency of 50% and 70%, respectively.     

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.     

Dry anaerobic digestion of high solids content dairy manure at high organic loading rates in psychrophilic sequence batch reactor

Cow manure with bedding is renewable organic biomass available around the year on dairy farms. Developing efficient and cost-effective psychrophilic dry anaerobic digestion (PDAD) processes could contribute to solving farm-related environmental, energy, and manure management problems in cold-climate regions. This study was to increase the organic loading rate (OLR), fed to a novel psychrophilic (20 °C) dry anaerobic digestion of 27 % total solid dairy manure (cow feces and wheat straw) in sequence batch reactor (PDAD-SBR), by 133 to 160 %. The PDAD-SBR process operated at treatment cycle length of 21 days and OLR of 7.0 and 8.0 g total chemical oxygen demand (TCOD)?kg^?1 inoculum day^?1 (5.2?±?0.1 and 5.8?±?0.0 g volatile solids (VS)?kg^?1 inoculum day^?1) for four successive cycles (84 days) produced average specific methane yields (SMYs) of 147.1?±?17.2 and 143.2?±?11.7 normalized liters (NL)?CH₄?kg^?1 VS fed, respectively. PDAD of cow feces and wheat straw is possible with VS-based inoculum-to-substrate ratio of 1.45 at OLR of 8.0 g TCOD kg^?1 inoculum day^?1. Hydrolysis was the limiting step reaction. The VS removal averaged around 57.4?±?0.5 and 60.5?±?5.7 % at OLR 7.0 and 8.0 g TCOD kg^?1 inoculum day^?1, respectively.     

The effects of digestion temperature and temperature shock on the biogas yields from the mesophilic anaerobic digestion of swine manure

In order to obtain basic design criteria for anaerobic digesters of swine manure, the effects of different digesting temperatures, temperature shocks and feed loads, on the biogas yields and methane content were evaluated. The digester temperatures were set at 25, 30 and 35 degrees C, with four feed loads of 5%, 10%, 20% and 40% (feed volume/digester volume). At a temperature of 30 degrees C, the methane yield was reduced by only 3% compared to 35 degrees C, while a 17.4% reduction was observed when the digestion was performed at 25 degrees C. Ultimate methane yields of 327, 389 and 403 mL CH(4)/g VS(added) were obtained at 25, 30 and 35 degrees C, respectively; with moderate feed loads from 5% to 20% (V/V). From the elemental analysis of swine manure, the theoretical biogas and methane yields at standard temperature and pressure were 1.12L biogas/g VS(destroyed) and 0.724 L CH(4)/g VS(destroyed), respectively. Also, the methane content increased with increasing digestion temperatures, but only to a small degree. Temperature shocks from 35 to 30 degrees C and again from 30 to 32 degrees C led to a decrease in the biogas production rate, but it rapidly resumed the value of the control reactor. In addition, no lasting damage was observed for the digestion performance, once it had recovered.