Improved anaerobic digestion of swine manure by simultaneous ammonia recovery using gas-permeable membranes.

In feedstocks containing high ammonia (NH3) concentration, removal of the NH3 during the anaerobic digestion (AD) process can improve AD process performance. In the present study, the effect of NH3 removal using gas-permeable membrane (GPM) technology on AD process performance and biogas production was investigated using swine manure feedstock. Batch and semi-continuous AD experiments were carried out under mesophilic conditions. In the reactor with NH3 recovery, total ammonia nitrogen (TAN) concentration was reduced 28% in batch experiments and 23% on average in the semicontinuous experiment compared with the reactor without NH3 recovery. Free ammonia (FA) concentrations were also decreased by 23% and 4% on average in batch and semicontinuous experiments, respectively. These reductions in TAN and FA by GPM system positively impacted both the quality and quantity of the biogas produced by AD of swine manure. Specifically, the specific methane yield increased 9% in the batch experiment and 17% on average in the semicontinuous experiment. Furthermore, higher percentages of methane in biogas were obtained during AD retrofitted with GPM system, 24% increase in the batch experiment and 11% on average in the semicontinuous experiment (range 8.3-13.6%). Simultaneously, a uniform TAN recovery rate of 6.7 g N TAN per m2 of membrane and per day was obtained for the 205 days of semicontinuous operation; ammonia nitrogen was recovered in the form of ammonium sulphate solution. Therefore, the AD-GPM configuration produces beneficial results on biogas quantity and quality while recovering ammonia nitrogen in form of ammonium sulphate.

Recovery of ammonia and phosphate minerals from swine wastewater using gas-permeable membranes.

Gas-permeable membrane technology is useful to recover ammonia (NH3) from liquid manures. In this study, phosphorus (P) recovery via MgCl2 precipitation was enhanced by combining it with NH3 recovery through gas-permeable membranes. Anaerobically digested swine wastewater containing approximately 2300 mg NH4+-N L-1 and 450 mg P L-1 was treated using submerged membranes plus low-rate aeration to recover the NH3 from within the liquid and MgCl2 to precipitate the P. The experiments included a first configuration where N and P were recovered sequentially and a second configuration with simultaneous recovery. The low-rate aeration reduced the natural carbonate, increased pH and accelerated NH3 uptake by the gas-permeable membrane system, which in turn benefited P recovery. Phosphorus removal efficiency was >90% and P recovery efficiency was about 100%. With higher NH3 capture, the recovered P contained higher P2O5 content (37-46%, >98% available), similar to the composition of the biomineral newberyite (MgHPO4·3H2O).

Enhancing recovery of ammonia from swine manure anaerobic digester effluent using gas-permeable membrane technology.

Gas-permeable membrane technology is useful to recover ammonia from manure. In this study, the technology was enhanced using aeration instead of alkali chemicals to increase pH and the ammonium (NH4(+)) recovery rate. Digested effluents from covered anaerobic swine lagoons containing 1465-2097 mg NH4(+)-N L(-1) were treated using submerged membranes (0.13 cm(2) cm(-3)), low-rate aeration (120 mL air L-manure(-1) min(-1)) and nitrification inhibitor (22 mg L(-1)) to prevent nitrification. The experiment included a control without aeration. The pH of the manure with aeration rose from 8.6 to 9.2 while the manure without aeration decreased from 8.6 to 8.1. With aeration, 97-99% of the NH4(+) was removed in about 5 days of operation with 96-98% recovery efficiency. In contrast, without aeration it took 25 days to treat the NH4(+). Therefore, the recovery of NH4(+) was five times faster with the low-rate aeration treatment. This enhancement could reduce costs by 70%.

Recovery of ammonia from swine manure using gas-permeable membranes: effect of waste strength and pH.

Nitrogen recovery from swine manure was investigated using gas-permeable membranes. The process involved a continuous recirculation of an acidic solution through a gas-permeable membrane submerged in manure. Ammonia from manure was concentrated in the acidic solution increasing its pH, while pH decreased in manure. In the first set of experiments, nitrogen recovery efficiency was evaluated with no pH adjustment of manure; whereas in the second, manure with three different ammonia (NH3) concentrations (from 1070 to 2290 mg/L) was used adjusting their pH to 9 whenever pH decreased below 7.7. With no pH adjustment, NH3 recovery from manure was 55%, while NH3 recovery averaged 81% when pH of manure was adjusted. This work showed that as waste strength and available NH3 content increased in manure, more N was captured by the membrane. These results suggested that the gas-permeable membranes are a useful technology for NH3 recovery from manure, reducing environmental pollution whilst converting NH3 into a valuable ammonium (NH4(+)) salt fertilizer.

Recovery of ammonia from swine manure using gas-permeable membranes: effect of aeration.

The gas-permeable membrane process can recover ammonia from manure, reducing pollution whilst converting ammonia into an ammonium salt fertilizer. The process involves manure pH control to increase ammonium (NH4(+)) recovery rate that is normally carried out using an alkali. In this study a new strategy to avoid the use of alkali was tested applying low-rate aeration and nitrification inhibition. The wastewater used was raw swine manure with 2390 mg NH4(+)-N/L. Results showed that aeration increased pH above 8.5 allowing quick transformation of NH4(+) into gaseous ammonia (NH3) and efficient recovery by permeation through the submerged membrane. The overall NH4(+) recovery obtained with aeration was 98% and ammonia emissions losses were less than 1.5%. The new approach can substitute large amounts of alkali chemicals needed to obtain high NH4(+) recovery with important economic and environmental savings.

Biofuels from microalgae: lipid extraction and methane production from the residual biomass in a biorefinery approach.

Renewable fuels and energy are of major concern worldwide and new raw materials and processes for its generation are being investigated. Among these raw materials, algae are a promising source of lipids and energy. Thus, in this work four different algae have been used for lipid extraction and biogas generation. Lipids were obtained by supercritical CO2 extraction (SCCO2), while anaerobic digestion of the lipid-exhausted algae biomass was used for biogas production. The extracted oil composition was analyzed (saturated, monounsaturated and polyunsaturated fatty acids) and quantified. The highest lipid yields were obtained from Tetraselmis sp. (11%) and Scenedesmus almeriensis (10%), while the highest methane production from the lipid-exhausted algae biomass corresponded to Tetraselmis sp. (236mLCH4/gVSadded).

In vitro assessment of thyroidal and estrogenic activities in poultry and broiler manure.

Among the many chemicals found in avian manure, endocrine disruptors (EDs), of natural or anthropogenic origin, are of special environmental concern. Nowadays, an increasing amount of estrogens is being released into the environment via the use of manure to fertilize agricultural land. While most research in this field has focused on estrogenic phenomena, little is known about alterations related to other endocrine systems, such as the thyroidal one. Here we simultaneously assessed the potential estrogenic and thyroidal activity of poultry and broiler litter manure using in vitro approaches based on estrogen receptor (Er) and thyroid receptor (Tr) transactivation assays. In addition, leaching experiments were performed to assess whether the EDs present in the manure pass through a soil column and potentially reach the groundwater. Manure from four broiler and four poultry farms was collected in two sampling campaigns carried out in two seasons (fall and spring). Extracts from broiler and poultry manure exhibited strong thyroidal activity. Only poultry manure showed estrogenic activity, which is consistent with the low levels of estrogens expected in hatchlings. Leakage experiments were performed in columns with two kinds of arable soils: sandy and loamy. No estrogenicity or thyroidal activity was detectable in soils treated with the manure or in the corresponding leachates. These results indicate that substances with estrogenic or thyroidal activity were degraded in the soil under our experimental conditions. However, the long-term effects associated with the constant and intensive application of manure to agricultural land in some regions require further research.

On-farm treatment of swine manure based on solid-liquid separation and biological nitrification-denitrification of the liquid fraction.

In some regions, intensive pig farming has led to soil and water pollution due to the over-application of manure as an organic fertilizer, thereby necessitating alternative treatment technologies to help manage the large amounts of manure generated. The present study seeks to determine the effectiveness of an on-farm swine manure treatment plant consisting of a solid-liquid separation phase using screw pressing followed by a coagulation-flocculation process, and nitrification-denitrification of the liquid fraction. Each treatment unit was evaluated for its contribution towards reducing the raw manure concentration of solids, organic matter, nutrients (nitrogen and phosphorous), metals, and pathogens. The overall system presented high removal efficiencies of up to 71% of TS (total solids) and 97% of TCOD (total chemical oxygen demand). Approximately 97% TKN (total Kjeldahl nitrogen) and 89% TP (total phosphorous) removal was achieved. Metals (copper and zinc) diminished in the liquid fraction to non-detectable concentrations (<1.0 mg L(-1)). As regards microbial removal, total concentration reductions of 3.6 log10 for Escherichia coli and 1.8 log10 for Salmonella were achieved. Finally, the system was evaluated from a financial standpoint. Results indicate that screw pressing and coagulation-flocculation for solid-liquid separation and nitrification-denitrification of the liquid fraction is a technological alternative for reducing the environmental impact of intensive pig farming in a given area.

Treatment of agro-industrial wastewater using microalgae-bacteria consortium combined with anaerobic digestion of the produced biomass.

Two combined processes were studied in order to produce second generation biofuels: microalgae biomass production and its further use to produce biogas. Two 5 L photobioreactors for treating wastewater from a potato processing industry (from now on RPP) and from a treated liquid fraction of pig manure (from now on RTE) were inoculated with Chlorella sorokiniana and aerobic bacteria at 24±2.7 °C and 6000 lux for 12 h per day of light supply. The maximum biomass growth was obtained for RTE wastewater, with 26.30 mg dry weight L(-1) d(-1). Regarding macromolecular composition of collected biomass, lipid concentration reached 30.20% in RPP and 4.30% in RTE. Anaerobic digestion results showed that methane yield was highly influenced by substrate/inoculum ratio and by lipids concentration of the biomass, with a maximum methane yield of 518 mL CH4 g COD(-1)added using biomass with a lipid content of 30% and a substrate/inoculum ratio of 0.5.

Treatment of fish processing wastewater with microalgae-containing microbiota.

Two photobioreactors inoculated with microalgae from a lagoon containing aerobically treated swine slurry and with sludge from a membrane submerged bioreactor treating winery wastewater were established to treat fish processing wastewater (FPW) at 23 and 31 °C, respectively. The hydraulic retention time (HRT) was decreased in the photobioreactors from 10 to 5 days. Ammonium was completely exhausted in both photobioreactors; however, volatilization was the main removal mechanism for the highest applied load whereas biomass assimilation was the main mechanism for the lowest applied load. Approximately 70% of TCOD (total chemical oxygen demand) and phosphate removal was achieved regardless of temperature. Biomass productivity was as much as 55% higher at 31 °C than at 23 °C. These results suggested that fish processing wastewater could be effectively treated using this technology.

Potential for methane production from anaerobic co-digestion of swine manure with winery wastewater.

This work examines the methane production potential for the anaerobic co-digestion of swine manure (SM) with winery wastewater (WW). Batch and semi-continuous experiments were carried out under mesophilic conditions. Batch experiments revealed that the highest specific methane yield was 348 mL CH(4)g(-1) COD added, obtained at 85.4% of WW and 0.7 g COD g(-1)VS. Specific methane yield from SM alone was 27 mL CH(4)g(-1) COD added d(-1). Furthermore, specific methane yields were 49, 87 and 107 mL CH(4)g(-1) COD added d(-1) for the reactors co-digesting mixtures with 10% WW, 25% WW and 40% WW, respectively. Co-digestion with 40% WW improved the removal efficiencies up to 52% (TCOD), 132% (SCOD) and 61% (VSS) compared to SM alone. These results suggest that methane can be produced very efficiently by the co-digestion of swine manure with winery wastewater.