In this study a single-well, "push- pull" test method is adapted for determination of in situ denitrification rates in groundwater aquifers. The rates of stepwise reduction of nitrate to nitrite, nitrous oxide, and molecular nitrogen were determined by performing a series of push-pull tests. The method consists of the controlled injection of a prepared test solution ("push") into an aquifer followed by the extraction of the test solution/ground water mixture ("pull") from the same location. The injected test solution consists of ground water containing a nonreactive tracer and one or more biologically reactive solutes. Reaction rate coefficients are computed from the mass of reactant consumed and/or product formed. A single Transport Test, one Biostimulation Test, and four Activity Tests were conducted for this study. Transport tests are conducted to evaluate the mobility of solutes used in subsequent tests. These included bromide (a conservative tracer), fumarate (a carbon and/or source), and nitrate (an electron acceptor). Extraction phase breakthrough curves for all solutes were similar, indicating apparent conservative transport of the solutes prior to biostimulation. Biostimulation tests were conducted to stimulate the activity of indigenous heterotrophic denitrifying microorganisms and consisted of injection of site ground water containing fumarate and nitrate. Biostimulation was detected by the simultaneous production of carbon dioxide and nitrite after each injection. Activity tests were conducted to quantify rates of nitrate, nitrite, and nitrous oxide reduction. Estimated zero-order degradation rates decreased in the order nitrate > nitrite > nitrous oxide. The series of push-pull tests developed and field tested in this study should prove useful for conducting rapid, low-cost feasibility assessments for in situ denitrification in nitrate-contaminated aquifers.

Nightsoil and piggery wastes generally present high strength organics and nitrogen. This study evaluated the nitrogen removal characteristics with the existing and modified nightsoil and piggery waste treatment plants. The existing conventional plants showed 20 to 40% nitrogen removal, but the modification with SBR or MLE process could remove effectively both nitrogen and organics with the minimum COD/TN and alkalinity/TN ratios of 6 and 3.6, respectively. Nitrite nitrification and denitrification rates obtainable at higher nitrogen loads were faster than the rates of nitrate nitrification and denitrification resulting in less reactor volume requirement. However, the higher nitrogen loads increased the organic loads resulting in the reactor temperature inhibiting nitrification. Thus, a combined treatment with anaerobic digestion with the adjustment of influent bypass rates was proposed to reduce the reactor temperature and the external carbon requirement. The biological treatment could discharge about 1,100 mg/L soluble COD and 50 mg/L soluble nitrogen, respectively.

Purpose In a novel approach, certain organic wastes byproducts of agro industries were assessed for their ability to support maize growth and Zn bioavailability in maize grain. Methods In a field experiment, maize (Zea mays) was supplemented with farm yard manure (FYM), press mud (PM), fisheries manure (FM), and slaughter house waste (SHW) in combination with Zn soil application (ZnS) and Zn foliar spray (ZnF) with recommended doses of N:P:K (140:100:60 kg ha −1 ), respectively. Besides assessing the maize growth, grain, and straw yield, Zn bioavailability in maize grain was also studied. Results Organic materials combined with ZnS and ZnF significantly increased the maize yield and Zn bioavailability. PM + ZnS increased the grain yield by 69.71%, while FM + ZnF and FYM + ZnF increased the grain Zn concentration by 86.37 and 86.16%, respectively. Moreover, grain Zn content was greatly influenced by PM + ZnS and PM + ZnF resulted an average increase by 160%. Phytate concentration and phytae:Zn molar ratio in grain were decreased by 30.34 and 66.92%, respectively by FYM + ZnF. Estimated Zn bioavailability ranged from 0.92 to 2.04 mg Zn/300 g in maize grain, and was maximum by PM and FYM combined with ZnF. Conclusion Organic manures influence the nutrient uptake from soil, increase the product quality, and act as a good organic fertilizer. The current study revealed that organic manures can enhance crop growth and Zn uptake in grain in sustainable manner. It would be an eco-friendly approach by utilizing organic wastes annually generated by agro industries.

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Swine wastewater effluent is a key source of water contamination since it contains high levels of nutrients, including nitrogen and phosphorus, as well as nitrates and refractory organic matter (ROM). ROM refers to organic compounds that are usually resistant to microbial degradation. When swine wastewater effluent containing high levels of ROM is subsequently discharged into rivers and streams without being adequately treated, purification costs for drinking water increase and there remains a possibility for harmful substances to enter the human body. In this study, we introduce new methods for setting total organic carbon (TOC) water quality standards for discharging swine wastewater effluent containing high levels of ROM after treatment. To set the TOC water quality standards, various analysis methods based on statistics, technology, and experience based on operational data of livestock-manure treatment facilities were applied. In addition, the achievability of the proposed TOC standards in livestock-manure treatment facilities and the financial burden of their implementation on livestock farms were also reviewed. Here, we set tentative values that include all of our results derived from each methodology and set the TOC standards to levels that can be achieved through the normal operation of swine-wastewater treatment facilities (60 mg/L for public treatment facilities and 140 mg/L for treatment facilities operated by individual farms). When setting TOC standards, both single and combined methodologies should be considered and employed after comprehensively assessing livestock management policies, regional conditions, and the burden on stakeholders.