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ABSTRACT: Most of Chinese middle size agricultural biogas plants run at the lower range of mesophilic conditions and low organic loading rates (OLRs) which result in the low biogas production. How to obtain an economically viable operation mode is a challenge for Chinese farm biogas plants. In this study, the performance of completely stirred anaerobic reactors treating pig manure was studied at 20, 28 and 38 °C. A thermal mathematic model was accordingly developed to decide the optimum digesting temperature and OLRs considering ambient temperature of 20, 10 and 0 °C. The regression surface model can fit well on the experimental data when the ambient temperature was around 10-20 °C, at which maximum net energy production (Np,max) can be achieved when the digesters run at OLR of 4.6-5.4 kgODM/m(3) d with temperature of above 26 °C. Co-digestion on the pig farm was suggested in winter in order to increase the Np.
Journal of Environmental Management 05/2013; 127C:18-22. · 3.24 Impact Factor
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ABSTRACT: A selection of six urine-derived struvite fertilizers generated by innovative precipitation technologies was assessed for their quality and their effectiveness as phosphorus sources for crops. Struvite purity was influenced by drying techniques and magnesium dosage. In a greenhouse experiment, the urine fertilizers led to biomass yields and phosphorus uptakes comparable to or higher than those induced by a commercial mineral fertilizer. Heavy metal concentrations of the different struvite fertilizers were below the threshold limits specified by the German Fertilizer and Sewage Sludge Regulations. The computed loading rates of heavy metals to agricultural land were also below the threshold limits decreed by the Federal Soil Protection Act. Urine-derived struvite contributed less to heavy metal inputs to farmland than other recycling products or commercial mineral and organic fertilizers. When combined with other soil conditioners, urine-derived struvite is an efficient fertilizer which covers the magnesium and more than half of the phosphorus demand of crops.
Chemosphere 08/2012; 89(10):1202-10. · 3.21 Impact Factor
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ABSTRACT: A No Mix sanitation system was installed in a dormitory at the University of Can Tho in Vietnam, with the objective of recycling nutrients from source separated urine. This paper presents a pilot scale evaporation technology, and investigates the feasibility of recovering nitrogen and phosphorus from human urine by solar still for use as fertilizer. After 26 days of sun exposure, 360 g of solid fertilizer material was recovered from 50 L undiluted urine. This urine-derived fertilizer was mainly composed of sodium chloride, and had phosphorus and nitrogen contents of almost 2%. When tested with maize and ryegrass, the urine fertilizer led to biomass yields and phosphorus and nitrogen uptakes comparable to those induced by a commercial mineral fertilizer. Urine acidification with sulfuric or phosphoric acid prior treatment reduced nitrogen losses, improved the nutrient content of the generated fertilizers, and induced higher biomass yields and nitrogen and phosphorus uptakes than the commercial mineral fertilizer. However, acidification is not recommended in developing countries due to additional costs and handling risks. The fate of micropollutants and the possibility of separating sodium chloride from other beneficial nutrients require further investigation.
Science of The Total Environment 12/2011; 414:592-9. · 3.29 Impact Factor
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CLEAN - Soil Air Water 10/2011; 39(12):1099 - 1104. · 2.18 Impact Factor
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ABSTRACT: Antibiotics of inorganic and organic origin in pig manure can inhibit the anaerobic process in biogas plants. The influence of three frequently used antibiotics, copper dosed as CuSO(4), sulfadiazine (SDZ), and difloxacin (DIF), on the anaerobic digestion process of pig manure was studied in semi-continuous experiments. Biogas production recovered after every Cu dosage up to a sum of 12.94g Cukg(-1) organic dry matter (ODM), probably due to Cu precipitation following the formation of sulphide from sulphate. Complete inhibition was found at the very high Cu concentration of 19.40g Cukg(-1) ODM. Inhibitory effect of SDZ and DIF was observed at concentrations as high as 2.70gkg(-1) ODM and 0.54gkg(-1) ODM, respectively. It seems very unlikely that the antibiotics tested would inhibit the anaerobic process in a full-scale biogas plant.
Waste Management 08/2011; 32(1):131-6. · 2.43 Impact Factor
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ABSTRACT: Septage is widely acknowledged as a major source of infectious pathogens while disposal of septage, and the operation and maintenance of septic tanks, is not regulated in many developing countries. Twenty untreated septage and septage sludge samples were taken from Can Tho City, Vietnam to examine their pathogen content, and indicator micro-organisms. Escherichia coli and Enterococcus spp. were detected in all samples, regardless of sludge storage time. Phages were detected in 80% of samples. Salmonella spp. were detected in 70% of the untreated septage and 60% of septage sludge samples. Concentrations of phages and bacteria tested in septage sludge after many years of tank storage were much higher than the expected levels. Helminth ova were present in 95% of untreated septage samples with an average of 450 oval(-1), and were detected in all septage sludge samples with an average of 16,000 oval(-1). Twelve varieties of helminth ova were identified. More helminth ova varieties in higher concentrations were found in septage than those reported from stool samples. The varieties' frequency ranged from 10% to 50% and Ascaris lumbricoides predominated. Results show that pathogens and indicator micro-organisms, especially helminth ova, accumulate in sludge. Thus helminth ova should be considered when septage sludge is treated and used for agriculture. Proper health protection measures must be applied for people handling septage.
Science of The Total Environment 02/2010; 408(9):2050-3. · 3.29 Impact Factor
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ABSTRACT: Human urine is a potential alternative fertilizer for agriculture. However, its usage is associated with a risk of spreading pharmaceutical residues to fields. The individual and combined behavior of carbamazepine and ibuprofen was investigated by GC/MS analysis in a greenhouse experiment using ryegrass fertilized with pharmaceutical-spiked urine. Only carbamazepine could be detected in soil, roots, and aerial plant parts. Fifty-three per cent of carbamazepine originally present in the urine was recovered in soil samples taken after three months. Additionally, 34% of carbamazepine was found in aerial plant parts and 0.3% in roots. Model calculations showed that neither roots nor Casparian strip posed a considerable barrier to uptake. Carbamazepine transport was clearly driven by transpiration. Ibuprofen was not detected in the soil or in any plant parts after three months. This was assumed to be due to biodegradation of ibuprofen. Carbamazepine and ibuprofen, singly or in combination, did not adversely affect the growth of ryegrass.
Science of The Total Environment 02/2010; 408(8):1902-8. · 3.29 Impact Factor
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ABSTRACT: Plastic plug-flow bio-digesters have been promoted as a good option for improved treatment of manure and wastewater in developing countries although minimal information has been published on their hygienic status. This bench-scale study replicates bio-digester conditions to evaluate the reduction of pathogen and indicator microorganisms at three different hydraulic retention times (HRT) in the anaerobic treatment of pig manures at 30 degrees C for 50 days. Results showed that physicochemical values differed between HRTs. Gas production efficiency was better for longer HRTS. The accumulated sludge at the reactor's base increased with longer HRT. Phages and bacteria examined were reduced, but none was completely eliminated. Log10 reduction of bacteria ranged from 0.54 to 2.47. Phages ranged from 1.60 to 3.42. The reduction of organisms at HRT = 30 days was about one log10 unit higher than HRT = 15 days and about two log10 units higher than HRT = 3 days. The results indicate that the reduction of tested organisms increases with HRT. However the hygienic quality of the liquid effluent does not meet required quality values for surface and irrigation water. Longer HRTs are recommended to increase gas yield and achieve higher pathogen reduction. More barriers should be applied while handling bio-digester outputs to minimise risks to environmental and human health.
Journal of Water and Health 08/2009; 7(4):590-6. · 1.37 Impact Factor
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ABSTRACT: The plant nutrients consumed in human society today are lost through the established wastewater treatment systems in industrialised countries as well as via insufficient or non-existent handling of sewage in the developing world. New sanitation systems have been designated to overcome this failure. The source separated wastewater streams collected within these systems contain a high nutrient content, and can be used as fertiliser as well as soil conditioner after appropriate storage and/or treatment. Application in agriculture with existing techniques is feasible. However, pathogens and pharmaceuticals contained in these fertiliser types are a potential hazard. Nevertheless, storage and appropriate treatment can minimise the risks. The products deriving from these systems have a high potential to preserve available plant nutrient resources and deficiencies in agriculture as well as being able to substitute synthetic plant nutrients and at the same time prevent unwanted environmental nutrient over-enrichment.
Bioresource technology 05/2009; 100(18):4090-6. · 4.25 Impact Factor
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ABSTRACT: Urine contains a considerable amount of nutrients and potentially could be used as supplement commercial mineral fertilizer; however, it carries risk of contamination. The effect of urine storage as a simple treatment method was examined under tropical conditions. Initial concentrations of total coliforms (2.3 x 10(5) CFU/100 mL), E. coli (<1.0 x 10(4) CFU/100 mL), and Salmonella sp. were less than detection limit after four weeks. Open storage led to nitrogen losses of 90%, whereas closed storage containers retained 93% of total nitrogen. Under storage, the N:P ratio of 8:1 in fresh urine changed to 14:1 in the supernatant and to 1:12 in the precipitate, and 100% of magnesium and 96% of calcium was precipitated. A model showed that, depending on plant requirements, using the mixture of supernatant and precipitate as fertilizer for crops such as cassava was reasonable. To fertilize crops such as rice, however, additional P and K was needed. The nutrient-based flux of heavy metals to soils was negligible.
Water Environment Research 82(9):840-7. · 0.88 Impact Factor
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ABSTRACT: The irrigation or agricultural land with wastewater is increasingly practiced in many parts of the world as a consequence of growing populations and urbanization. The risks emerging from pharmaceuticals that are contained in wastewater for soils and groundwater have hardly been investigated. We studied leaching and effects of naproxen, ibuprofen, bezafibrate, diclofenac, gemfibrocil, clarithromycin, trimethoprim, clindamycin, erythromycin, and metoprolol in a soil column experiment simulating an irrigation event with 8.6 cm of wastewater containing 20 microg L(-1) or 2000 microg L(-1) of each compound or of erythromycin alone. The leached fraction of applied pharmaceuticals ranged from 0.1 +/- 0.1% (clarithromycin, 2000 microg L(-1)) to 130 +/- 41% (naproxen, 20 microg L(-1)) and tended to increase with decreasing K(d) or K(oc). Naproxen transport was similar to that of the tracer chloride. Ibuprofen was also hardly retarded (R = 1.20 +/- 0.18), but showed a higher degradation rate of 0.02 +/- 0.004 h(-1) (2000 microg L(-1)) than naproxen. The transport of a pulse of 2000 microg L(-1) of bezafibrate could be described with a retardation factor of 1.5 and a degradation rate of 0.033 h(-1). The application of erythromycin alone or of a cocktail of all pharmaceuticals significantly increased soil CO2 emissions by 50% 1 d after the application. There is a considerable risk that pharmaceuticals are leached to groundwater during wastewater irrigation.
Journal of Environmental Quality 39(4):1201-10. · 2.32 Impact Factor
