Effect of anaerobic digester inoculum preservation via lyophilization on methane recovery.

A robust anaerobic digestion (AD) inoculum is key to a successful digestion process by providing the abundant bacteria needed for converting substrate to useable methane (CH4). While transporting digester contents from one AD to another for digester startup has been the norm, transportation costs are high, and it is not feasible to transport wet inoculum to remote locations. In this study, the impact of preservation of AD inoculum via lyophilization was investigated for the purposes of digester startup and restabilization. The effect of lyophilizing inoculum on CH4 production using food waste as the substrate was tested using biochemical methane potential (BMP) tests under the following conditions: (1) three inoculum sources, (2) two inoculum to substrate ratios (ISR), (3) two cryoprotectants, and (4) two inoculum growth phases. After lyophilization with skim milk, the three inocula produced 144-146 mL CH4/g volatile solids (VS) and 194-225 mL CH4/g VS at a 2:1 and 4:1 ISR, respectively, with 33-57% more CH4 at the 4:1 ISR. Preservation with 10% skim milk exhibited complete recovery of CH4 production, while 10% glycerol and 10% glycerol/skim milk mixture yielded 76% and 4% CH4 recovery, respectively. Inoculum growth phase before preservation (mid-exponential or stationary growth phase) did not significantly affect CH4 recovery. The study indicates that inoculum can be preserved via lyophilization using 10% skim milk as a cryoprotectant and reactivated for food waste digestion. The results provide a systematic quantification of the conditions needed to successfully preserve a mixed AD inoculum.

The fate and effect of monensin during anaerobic digestion of dairy manure under mesophilic conditions.

There is growing concern about residual antibiotics and feed additives in the manure of treated animals because of the effects of these residues in the environment. Monensin is the most widely used ionophore coccidiostat in the U.S. The objective of this study was to determine the fate and effect of monensin during the anaerobic digestion of dairy manure. Duplicate plug flow field-scale digesters were operated using non-amended dairy manure and dairy manure amended with monensin to 1 and 10 mg/L for 56 days at 30°C at an organic loading rate of 1.4 kg VS/m3-d and 17-day hydraulic retention time. Results showed that monensin was reduced approximately 70% during anaerobic digestion. Methane production from digesters using manure amended with 1 mg/L monensin was comparable to that from digesters operated without added monensin. However, digesters using manure amended with 10 mg/L monensin yielded 75% less methane than digesters using manure without added monensin. These results suggest that anaerobic digestion is an effective treatment for reducing, but not eliminating, monensin in dairy manure. Monensin did not reduce methane production at concentrations expected in dairy manure at recommended dosage rates.

Temporal Stability of Escherichia coli Concentrations in Waters of Two Irrigation Ponds in Maryland.

Fecal contamination of water sources is an important water quality issue for agricultural irrigation ponds. Escherichia coli concentrations are commonly used to evaluate recreational and irrigation water quality. We hypothesized that there may exist temporally stable spatial patterns of E. coli concentrations across ponds, meaning that some areas mostly have higher and other areas mostly lower than average concentrations of E. coli To test this hypothesis, we sampled two irrigation ponds in Maryland at nodes of spatial grids biweekly during the summer of 2016. Environmental covariates-temperature, turbidity, conductivity, pH, dissolved oxygen, chlorophyll a, and nutrients-were measured in conjunction with E. coli concentrations. Temporal stability was assessed using mean relative differences between measurements in each location and averaged measurements across ponds. Temporally stable spatial patterns of E. coli concentrations and the majority of environmental covariates were expressed for both ponds. In the pond interior, larger relative mean differences in chlorophyll a corresponded to smaller mean relative differences in E. coli concentrations, with a Spearman's rank correlation coefficient of 0.819. Turbidity and ammonium concentrations were the two other environmental covariates with the largest positive correlations between their location ranks and the E. coli concentration location ranks. Tenfold differences were found between geometric mean E. coli concentrations in locations that were consistently high or consistently low. The existence of temporally stable patterns of E. coli concentrations can affect the results of microbial water quality assessment in ponds and should be accounted for in microbial water quality monitoring design.IMPORTANCE The microbial quality of water in irrigation water sources must be assessed to prevent the spread of microbes that can cause disease in humans because of produce consumption. The microbial quality of irrigation water is evaluated based on concentrations of Escherichia coli as the indicator organism. Given the high spatial and temporal variability of E. coli concentrations in irrigation water sources, recommendations are needed on where and when samples of water have to be taken for microbial analysis. This work demonstrates the presence of a temporally stable spatial pattern in the distributions of E. coli concentrations across irrigation ponds. The ponds studied had zones where E. coli concentrations were mostly higher than average and zones where the concentrations were mostly lower than average over the entire observation period, covering the season when water was used for irrigation. Accounting for the existence of such zones will improve the design and implementation of microbial water quality monitoring.

Effect of liquid surface area on hydrogen sulfide oxidation during micro-aeration in dairy manure digesters.

Although there are a variety of commercially available biological and chemical treatments for removal of hydrogen sulfide (H2S) from biogas, managing biogas H2S remains a significant challenge for agricultural digesters where labor and operational funds are very limited compared to municipal and industrial digesters. The objectives of this study were to evaluate headspace aeration for reducing H2S levels in low cost plug flow digesters and to characterize the relationship between the liquid surface area and H2S oxidation rates. Experiments with replicate field scale plug flow digesters showed that H2S levels decreased from 3500 ppmv to <100 ppmv when headspace oxygen levels were 0.5 to 1%. Methane production was not affected by aeration rates that resulted in headspace oxygen levels of up to 1%. Pilot scale experiments using 65 to 104 L desulfurization units showed that H2S oxidation rates increased with increases in liquid surface area. These results support the hypothesis that H2S oxidation rates are limited, in part, by the surface area available for oxygen transfer, and can be increased by growth of biofilms containing H2S oxidizing bacteria. Maximum removal rates corresponded to 40 to 100 g S m-2 d-1 of liquid surface area at biogas retention times of 30 to 40 min.

The effect of composting on the persistence of four ionophores in dairy manure and poultry litter.

Manure composting is a well-described approach for stabilization of nutrients and reduction of pathogens and odors. Although composting studies have shown that thermophilic temperatures and aerobic conditions can increase removal rates of selected antibiotics, comparable information is lacking for many other compounds in untreated or composted manure. The objective of this study was to determine the relative effectiveness of composting conditions to reduce concentrations of four widely used ionophore feed supplements in dairy manure and poultry litter. Replicate aliquots of fresh poultry litter and dairy manure were amended with monensin, lasalocid, salinomycin, or amprolium to 10mgkg(-1)DW. Non-amended and amended dairy manure and poultry litter aliquots were incubated at 22, 45, 55, or 65°C under moist, aerobic conditions. Residue concentrations were determined from aliquots removed after 1, 2, 4, 6, 8, and 12weeks. Results suggest that the effectiveness of composting for contaminant reduction is compound and matrix specific. Composting temperatures were not any more effective than ambient temperature in increasing the rate or extent of monensin removal in either poultry litter or dairy manure. Composting was effective for lasalocid removal in poultry litter, but is likely to be too slow to be useful in practice (8-12weeks at 65°C for >90% residue removal). Composting was effective for amprolium removal from poultry litter and salinomycin in dairy manure but both required 4-6weeks for >90% removal. However, composting did not increase the removal rates or salinomycin in poultry litter or the removal rates of lasalocid or amprolium in dairy manure.

Effect of temperature on methane production from field-scale anaerobic digesters treating dairy manure.

Temperature is a critical factor affecting anaerobic digestion because it influences both system heating requirements and methane production. Temperatures of 35-37°C are typically suggested for manure digestion. In temperate climates, digesters require a considerable amount of additional heat energy to maintain temperatures at these levels. In this study, the effects of lower digestion temperatures (22 and 28°C), on the methane production from dairy digesters were evaluated and compared with 35°C using duplicate replicates of field-scale (FS) digesters with a 17-day hydraulic retention time. After acclimation, the FS digesters were operated for 12weeks using solids-separated manure at an organic loading rate (OLR) of 1.4kgVSm(-3)d(-1) and then for 8weeks using separated manure amended with manure solids at an OLR of 2.6kgVSm(-3)d(-1). Methane production values of the FS digesters at 22 and 28°C were about 70% and 87%, respectively, of the values from FS digesters at 35°C. The results suggest that anaerobic digesters treating dairy manure at 28°C were nearly as efficient as digesters operated at 35°C, with 70% of total methane achievable at 22°C. These results are relevant to small farms interested in anaerobic digestion for methane reduction without heat recovery from generators or for methane recovery from covered lagoon digesters.

Anaerobic co-digestion of forage radish and dairy manure in complete mix digesters.

Pilot-scale digesters (850 L) were used to quantify CH4 and H2S production when using forage radish cover crops as a co-digestion feedstock in dairy manure-based digesters. During two trials, triplicate mixed digesters were operated in batch mode with manure-only or radish+manure (27% and 13% radish by wet weight in Trial 1 and 2, respectively). Co-digestion increased CH4 production by 11% and 39% in Trial 1 and 2, respectively. As H2S production rapidly declined in the radish+manure digesters, CH4 production increased reaching high levels of CH4 (⩾67%) in the biogas. Over time, radish co-digestion lowered the H2S concentration in the biogas (0.20%) beyond that of manure-only digestion (0.34-0.40%), although cumulative H2S production in the radish+manure digesters was higher than manure-only. Extrapolated to a farm-scale (200 cows) continuous mixed digester, co-digesting with radish could generate 3150 m(3) CH4/month, providing a farmer additional revenue up to $3125/month in electricity sales.

Pathogen reduction in minimally managed composting of bovine manure.

Spread of manure pathogens is of considerable concern due to use of manure for land application. In this study, the effects of four static pile treatment options for bovine manure on die-off of a generic Escherichia coli, E. coli O157:H7 surrogate, Salmonella Senftenberg, Salm. Typhimurium, and Listeria monocytogenes were evaluated. Bovine manure spiked with these bacteria were placed in cassettes at the top, middle, and bottom sections of four static pile treatments that reflect minimal changes in pile construction with and without straw. Temperatures were monitored continuously during the 28 day self-heating period. E. coli and salmonellae were reduced from 8 to 9 log10 CFU g(-1) to undetectable levels (<1.77 log10 MPN g(-1)) at 25-30 cm depths within 7 days in all pile sections except for the manure-only pile in which 3-4 logs of reduction were obtained. No L. monocytogenes initially present at 6.62 log10 CFU g(-1) were recovered from straw-amended piles after 14 days, in contrast with manure-only treatment in which this pathogen was recovered even at 28 days. Decline of target bacterial populations corresponded to exposure to temperatures above 45°C for more than 3 days and amendments of manure with straw to increase thermophilic zones. Use of straw to increase aeration, self-heating capacity, and heat retention in manure piles provides producers a minimal management option for composting that enhances pathogen die-off and thereby reduces risk of environmental spread when manure is applied to land.

Nutrient removal from agricultural drainage water using algal turf scrubbers and solar power.

The objectives of this study were to determine nutrient removal rates and costs using solar-powered algal turf scrubber (ATS) raceways and water from an agricultural drainage ditch. Algal productivity using daytime-only flow was 3-lower compared to productivity using continuous flow. Results from this and other studies suggest a non-linear relationship between flow rate and nitrogen removal rates. Nitrogen (N) and phosphorus (P) removal rates averaged 125 mg N, 25 mg P m(-2) d(-1) at the highest flow rates. Nutrient removal rates were equivalent to 310 kg N and 33 kg P ha(-1) over a 7 month season. Projected nutrient removal costs ($90-$110 kg(-1) N or $830-$1050 kg(-1) P) are >10-fold higher than previous estimates for ATS units used to treat manure effluents.

Performance of compost filtration practice for green infrastructure stormwater applications.

Urban storm water runoff poses a substantial threat of pollution to receiving surface waters. Green infrastructure, low impact development, green building ordinances, National Pollutant Discharge Elimination System (NPDES) storm water permit compliance, and Total Maximum Daily Load (TMDL) implementation strategies have become national priorities; however, designers need more sustainable, low-cost solutions to meet these goals and guidelines. The objective of this study was to determine the multiple-event removal efficiency and capacity of compost filter socks (FS) and filter socks with natural sorbents (NS) to remove soluble phosphorus, ammonium-nitrogen, nitrate-nitrogen, E. coli, Enterococcus, and oil from urban storm water runoff. Treatments were exposed to simulated storm water pollutant concentrations consistent with urban runoff originating from impervious surfaces, such as parking lots and roadways. Treatments were exposed to a maximum of 25 runoff events, or when removal efficiencies were < or = 25%, whichever occurred first. Experiments were conducted in triplicate. The filter socks with natural sorbents removed significantly greater soluble phosphorus than the filter socks alone, removing a total of 237 mg/linear m over eight runoff events, or an average of 34%. The filter socks with natural sorbents removed 54% of ammonium-nitrogen over 25 runoff events, or 533 mg/linear m, and only 11% of nitrate-nitrogen, or 228 mg/linear m. The filter socks and filter socks with natural sorbents both removed 99% of oil over 25 runoff events, or a total load of 38,486 mg/linear m. Over 25 runoff events the filter socks with natural sorbents removed E. coli and Enteroccocus at 85% and 65%, or a total load of 3.14 CFUs x 10(8)/ linear m and 1.5 CFUs x 10(9)/linear m, respectively; both were significantly greater than treatment by filter socks alone. Based on these experiments, this technique can be used to reduce soluble pollutants from storm water over multiple runoff events.

Use of mid- and near-infrared spectroscopy to track degradation of bio-based eating utensils during composting.

Near-infrared spectroscopy (NIRS) and mid-infrared spectroscopy (MIRS) have been used for quantitative and/or qualitative analysis of a wide range of materials. The objective of this study was to investigate the potential of MIRS and NIRS for following the degradation of bio-based food utensils during composting. Polylactide (PLA)-based forks lost 34% of their initial mass and were reduced to small friable fragments after 7 weeks of composting. NIRS and MIRS spectra of forks that were incubated for 7 weeks were nearly identical to spectra of untreated forks. NIRS and MIRS were more useful in following the degradation of a starch/polypropylene (PP) polymer. Spectral results demonstrated that the starch component degraded during composting and that the PP component was recalcitrant. These results confirm that MIRS and NIRS are useful in determining the composition of biobased materials. However, the spectra did not provide useful information about the extent of PLA polymer degradation.

Use of an algal hydrolysate to improve enzymatic hydrolysis of lignocellulose.

This study investigated the use of acid hydrolyzed algae to enhance the enzymatic hydrolysis of lignocellulosic biomass. The farm-waste grown algal samples were first characterized, and the optimal conditions for algal hydrolysis using dilute sulfuric acid were determined. Neutralized algal hydrolysate was then tested as a reaction medium (replacing the pH buffer solution) for the enzymatic hydrolysis of a lignocellulose, alkali treated anaerobically-digested fiber. Our results showed that net glucose yields from enzymatic hydrolyses containing undiluted algal hydrolysate were at least 65% higher than net glucose yields from control media (bovine serum albumin solution, citrate buffer or distilled water). It is likely that the increase in net glucose yield is due, in part, to the binding of hydrolyzed algal proteins to lignin, which protects cellulase from binding to lignin. This study demonstrates a potential approach of using wastewater-grown algae as a co-substrate to significantly enhance the enzymatic hydrolysis of lignocellulosic materials.

Minimally managed composting of beef manure at the pilot scale: effect of manure pile construction on pile temperature profiles and on the fate of oxytetracycline and chlortetracycline.

Oxytetracycline (OTC) and chlortetracycline (CTC) are broad-spectrum antibiotics used in livestock production. Although laboratory-scale studies have shown that extractable concentrations of these compounds decrease over time within treated and untreated manures and soils, there is relatively little information from farm-scale experiments. The objective of this study was to determine the effect of different levels of management on manure pile temperature profiles and on the fate of OTC and CTC in manure from therapeutically treated calves. Four treatments were designed to span a range of management options - from simply piling up the manure to amending it with straw to increase aeration and adding insulating layers of straw. Replicate samples of antibiotic-containing calf manure were held at ambient temperature or placed in three locations within replicate 3m(3) piles of beef manure. During the 28-day incubation period, concentrations of buffer-extractable OTC and CTC/ECTC (the summed concentrations of CTC and its epimer 4-epi-chlortetracycline (ECTC)) in manure samples incubated at ambient temperature (11-24 degrees C) decreased 75% (from 18 to 4.6 mg kg(-1) dry weight (DW)) and 90% (from 192 to 16 mg kg(-1) DW), respectively. Concentrations of the CTC metabolite iso-chlortetracycline (ICTC) decreased 90% (from 37 to 3 mg kg(-1) DW). OTC and CTC/ECTC concentrations in samples incubated for 28 days within a non-amended manure pile decreased 91% and >99%, respectively. During that period, the manure pile temperature ranged from 36 degrees C to 45 degrees C. Manure piles insulated with a blanket of straw and/or amended with straw (3:1, v/v) attained temperatures up to 70 degrees C and contained very low levels of OTC, CTC/ECTC, and ICTC (ranging from <0.1 to 0.4 mg kg(-1) DW) after 28 days.

Management of antibiotic residues from agricultural sources: use of composting to reduce chlortetracycline residues in beef manure from treated animals.

Chlortetracycline (CTC) is one of only ten antibiotics licensed in the U.S.A. for use as growth promoters for livestock. The widespread use and persistence of CTC may contribute in development of antibiotic-resistant bacteria. The objective of this study was to determine the effect of composting on the fate of CTC residues found in manure from medicated animals. The effect of CTC residues on composting was also investigated. Five beef calves were medicated for 5 days with 22 mg/kg/day of CTC. Manure samples collected from calves prior to and after medication were mixed with straw and woodchips, and aliquots of the subsequent mixtures were treated in laboratory composters for 30 days. In addition, aliquots of the CTC-containing mixture were incubated at 25 degrees C or sterilized followed by incubation at 25 degrees C and 55 degrees C (composting temperature). The presence of CTC did not appear to affect the composting process. Concentrations of CTC/ECTC (the summed concentrations of CTC and its epimer ECTC) in the composted mixture (CM) and sterilized mixture incubated at 55 degrees C (SM55) decreased 99% and 98% (from 113 microg/g dry weight (DW) to 0.7 microg/g DW and 2.0 microg/g DW), respectively, in 30 days. In contrast, levels of CTC/ECTC in room temperature incubated (RTIM) and sterilized mixture incubated at 25 degrees C (SM25) decreased 49% and 40% (to 58 microg/g DW and 68 microg/g DW), respectively, after 30 days. Concentrations of the CTC metabolite, iso-chlortetracycline (ICTC), in CM and SM55 decreased more than 99% (from 12 microg/g DW to below quantitation limit of 0.3 microg/g DW) in 30 days. ICTC levels in RTIM and SM25 decreased 80% (to 4 microg/g DW) in 30 days. These results confirm and extend those from previous studies that show the increased loss of extractable CTC residues with increased time and incubation temperature. In addition, our results using sterile and non-sterile samples suggest that the decrease in concentrations of extractable CTC/ECTC at 25 degrees C and 55 degrees C (composting temperature) is due to abiotic processes.

Treatment of dairy manure effluent using freshwater algae: algal productivity and recovery of manure nutrients using pilot-scale algal turf scrubbers.

Cultivating algae on nitrogen (N) and phosphorus (P) in animal manure effluents presents an alternative to the current practice of land application. The objective of this study was to determine values for productivity, nutrient content, and nutrient recovery using filamentous green algae grown in outdoor raceways at different loading rates of raw and anaerobically digested dairy manure effluent. Algal turf scrubber raceways (30m2 each) were operated in central Maryland for approximately 270 days each year (roughly April 1-December 31) from 2003 to 2006. Algal biomass was harvested every 4-12 days from the raceways after daily additions of manure effluent corresponding to loading rates of 0.3 to 2.5g total N (TN) and 0.08 to 0.42g total P (TP) m(-2)d(-1). Mean algal productivity values increased from approximately 2.5g DW m(-2)d(-1) at the lowest loading rate (0.3g TN m(-2)d(-1)) to 25g DW m(-2)d(-1) at the highest loading rate (2.5g TN m(-2)d(-1)). Mean N and P contents in the dried biomass increased 1.5-2.0-fold with increasing loading rate up to maximums of 7% N and 1% P (dry weight basis). Although variable, algal N and P accounted for roughly 70-90% of input N and P at loading rates below 1g TN, 0.15g TP m(-2)d(-1). N and P recovery rates decreased to 50-80% at higher loading rates. There were no significant differences in algal productivity, algal N and P content, or N and P recovery values from raceways with carbon dioxide supplementation compared to values from raceways without added carbon dioxide. Projected annual operational costs are very high on a per animal basis ($780 per cow). However, within the context of reducing nutrient inputs in sensitive watersheds such as the Chesapeake Bay, projected operational costs of $11 per kgN are well below the costs cited for upgrading existing water treatment plants.

Composting rapidly reduces levels of extractable oxytetracycline in manure from therapeutically treated beef calves.

Oxytetracycline (OTC) is a broad-spectrum antibiotic used in livestock production. The widespread use and relative persistence of OTC may encourage development of antibiotic-resistant bacteria. The objective of this study was to determine whether composting would substantially reduce the concentration of OTC found in manure from medicated animals. The effect of OTC on composting was also investigated. Five beef calves were medicated for 5 days with 22 mg/kg/day of OTC. Approximately 23% of the OTC fed to the calves was recovered in the manure. Manure samples collected from calves prior to and after medication were mixed with straw and woodchips, and aliquots of the subsequent mixtures were treated in laboratory composters for 35 days. In addition, aliquots of the OTC-containing mixture were incubated at 25 degrees C or sterilized followed by incubation at 25 degrees C. The presence of OTC did not appear to affect composting processes. Within the first six days of composting, levels of extractable OTC in the compost mixture decreased from 115+/-8 microg/g dry weight to less than 6+/-1 microg/g dry weight (a 95% reduction). In contrast, levels of extractable OTC in room temperature incubated and sterilized mixtures decreased only 12-25% after 37 and 35 days, respectively. Levels of total heterotrophic bacteria and OTC-resistant bacteria in the finished compost mixture were roughly 30-fold higher and 10-fold lower, respectively, than levels in the mixture prior to composting. Although the basis of the OTC disappearance during composting is not known, the preponderence of OTC-sensitive bacteria and the decrease of OTC-resistant bacteria in the finished compost suggests that OTC residues have been rendered biologically inactive or unavailable.

Recycling of manure nutrients: use of algal biomass from dairy manure treatment as a slow release fertilizer.

An alternative to land spreading of manure is to grow crops of algae on the N and P present in the manure and convert manure N and P into algal biomass. The objective of this study was to evaluate the fertilizer value of dried algal biomass that had been grown using anaerobically digested dairy manure. Results from a flask study using two soils amended with algal biomass showed that 3% of total algal nitrogen (N) was present as plant available N at day 0. Approximately 33% of algal N was converted to plant available N within 21 days at 25 degrees C in both soils. Levels of Mehlich-3 extractable phosphorus (P) in the two soils rose with increasing levels of algal amendment but were also influenced by existing soil P levels. Results from plant growth experiments showed that 20-day old cucumber and corn seedlings grown in algae-amended potting mix contained 15-20% of applied N, 46-60% of available N, and 38-60% of the applied P. Seedlings grown in algae-amended potting mixes were equivalent to those grown with comparable levels of fertilizer amended potting mixes with respect to seedling dry weight and nutrient content. These results suggest that dried algal biomass produced from treatment of anaerobically digested dairy manure can substitute for commercial fertilizers used for potting systems.

Treatment of dairy manure effluent using freshwater algae: elemental composition of algal biomass at different manure loading rates.

The cultivation of algae on nitrogen (N) and phosphorus (P) in animal manure effluents presents an alternative to the current practice of land application. However, the use and value of the resulting algal biomass as a feed or soil supplement depend, in part, on whether the biomass contains any harmful components such as heavy metals. The objective of this study was to determine how the elemental composition of algae changed in response to different loading rates of anaerobically digested flushed dairy manure effluent. Algal biomass was harvested weekly from laboratory-scale algal turf scrubber (ATS) units using four manure loading rates (2, 4, 6, or 9 L m(-2) day(-1)) corresponding to daily loading rates of 0.8-3.7 g of total N and 0.12-0.58 g of total P. Mean N and P contents in the dried biomass increased 1.6-1.8-fold with increasing loading rate up to maximums of 6.5% N and 0.84% P at 6 L m(-2) day(-1). Concentrations of Al, Ca, Cu, Fe, Mg, Mn, and Zn showed similar 1.4-1.8-fold increases up to maximums at a loading rate of 6 L m(-2) day(-1), followed by plateaus or decreases above this loading rate. Concentrations of Cd, Mo, and Pb initially increased with loading rate but then declined to levels comparable to those at the lowest loading rate. Concentrations of Si and K did not increase significantly with loading rate. The maximum concentrations of individual components in the algal biomass were as follows (in mg kg(-)(1)): 1100 (Al), 9700 (Ca), 0.43 (Cd), 56 (Cu), 580 (Fe), 5.0 (Pb), 2300 (Mg), 240 (Mn), 3.0 (Mo), 14,700 (K), 210 (Si), and 290 (Zn). At these concentrations, heavy metals in the algal biomass would not be expected to reduce its value as a soil or feed amendment.

Recovery of dairy manure nutrients by benthic freshwater algae.

Harnessing solar energy to grow algal biomass on wastewater nutrients could provide a holistic solution to nutrient management problems on dairy farms. The production of algae from a portion of manure nutrients to replace high-protein feed supplements which are often imported (along with considerable nutrients) onto the farm could potentially link consumption and supply of on-farm nutrients. The objective of this research was to assess the ability of benthic freshwater algae to recover nutrients from dairy manure and to evaluate nutrient uptake rates and dry matter/crude protein yields in comparison to a conventional cropping system. Benthic algae growth chambers were operated in semi-batch mode by continuously recycling wastewater and adding manure inputs daily. Using total nitrogen (TN) loading rates of 0.64-1.03 g m(-2) d(-1), the dried algal yields were 5.3-5.5 g m(-2) d(-1). The dried algae contained 1.5-2.1% P and 4.9-7.1% N. At a TN loading rate of 1.03 g m(-2) d(-1), algal biomass contained 7.1% N compared to only 4.9% N at a TN loading rate of 0.64 g m(-2) d(-1). In the best case, algal biomass had a crude protein content of 44%, compared to a typical corn silage protein content of 7%. At a dry matter yield of 5.5 g m(-2) d(-1), this is equivalent to an annual N uptake rate of 1,430 kg ha(-1) yr(-1). Compared to a conventional corn/rye rotation, such benthic algae production rates would require 26% of the land area requirements for equivalent N uptake rates and 23% of the land area requirements on a P uptake basis. Combining conventional cropping systems with an algal treatment system could facilitate more efficient crop production and farm nutrient management, allowing dairy operations to be environmentally sustainable on fewer acres.

Enhanced-rate biodegradation of organophosphate neurotoxins by immobilized nongrowing bacteria.

Pesticide wastes generated from livestock dipping operations containing the organophosphate (OP) insecticide coumaphos (CP) are well suited for disposal by biodegradation since they are highly concentrated (approximately 1 g/L), generally contained, and lack additional toxic components. In this study, a significantly enhanced efficiency of degrading CP in cattle dip waste (CDW) is reported using a dense, nongrowing cell population that functions without the addition of nutrients required for growing cell cultures. A recombinant strain of Escherichia coli containing the opd gene for organophosphate hydrolase (OPH), which is capable of active hydrolysis of OP neurotoxins including CP, was cultivated in a rich medium containing all essential nutrients. Cells were harvested and utilized in lab scale experiments in the form of either freely suspended cells or cells immobilized within a macroporous gel matrix, poly(vinyl alcohol) (PVA) cryogel. Significantly higher degradation rates were achieved with either suspended or immobilized OPH(+) cells compared to rates with the microbial consortium naturally present in CDW. Of the two nongrowing cell systems, the detoxification rate with immobilized cells was approximately twice that of freely suspended cells, and kinetic studies demonstrated that a higher maximum reaction rate was achieved with the immobilized cell system. A comparative study using both the CDW and pure CP substrates with free cells indicated that the CDW contained one or more factors that reduced the bioavailability of CP. The immobilized cells retained their activity over a 4-month period of use and storage, demonstrating both sustained catalytic activity and long-term mechanical stability.