High speed municipal sewage treatment in microbial fuel cell integrated with anaerobic membrane filtration system

A cylindrical two chambered microbial fuel cell (MFC) integrated with an anaerobic membrane filter was designed and constructed to evaluate bioelectricity generation and removal efficiency of organic substrate (glucose or domestic wastewater) depending on organic loading rates (OLRs). The MFC was continuously operated with OLRs 3.75, 5.0, 6.25, and 9.38 kg chemical oxygen demand (COD)/(m(3)·d) using glucose as a substrate, and the cathode chamber was maintained at 5-7 mg/L of dissolved oxygen. The optimal OLR was found to be 6.25 kgCOD/(m(3)·d) (hydraulic retention time (HRT) 1.9 h), and the corresponding voltage and power density averaged during the operation were 0.15 V and 13.6 mW/m(3). With OLR 6.25 kgCOD/(m(3)·d) using domestic wastewater as a substrate, the voltage and power reached to 0.13 V and 91 mW/m(3) in the air cathode system. Even though a relatively short HRT of 1.9 h was applied, stable effluent could be obtained by the membrane filtration system and the following air purging. In addition, the short HRT would provide economic benefit in terms of reduction of construction and operating costs compared with a conventional aerobic treatment process.

Economical and technical efficiencies evaluation of full scale piggery wastewater treatment BNR plants

A method evaluating the economic efficiency of piggery waste treatment plant based on kinetics for nitrogen removal performances is executed in this study and five full scale plants were evaluated, monitored intensively during one year under steady-state conditions. The performance data from those surveyed plants were recalculated by first-order kinetic equation instead of the Monod's equation, and the nitrogen removal kinetics related with COD/TKN ratios. Two plants adapting two extreme strategies for pre treatment, 'excess phase separation', and 'minimum phase separation', were evaluated by the assessment of life cycle cost (LCC). Although the compared two plants use an opposite strategy to each other, similar evaluation results are deduced by nitrogen removal efficiencies and operational and construction costs. But the proportions of constituent elements are as different as two opposite strategies, so electrical and construction costs are inversely proportional to chemical costs and operational costs respectively.

A single well push-pull test method for in situ determination of denitrification rates in a nitrate-contaminated groundwater aquifer

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.

High strength nitrogen removal from nightsoil and piggery wastes

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.

Application of piggery waste to nightsoil plant towards sustainable development

Organic loads have been significantly reduced in nightsoil plants along with the employment of sewage treatment plants. Nightsoil consisting of 10% septage and showing higher ratios of alkalinity and carbon to nitrogen helped nitrification and denitrification for those combined plants with week piggery waste. However, alkalinity and carbon addition was necessary with the weak nightsoil consisting of 80% septage when the combined influent was less than 21 g/L COD. The piggery waste could be applied at a rate of 0.5 kgTKN/oxic m3/d, but the organic load should be limited to 0.7 kgCOD/m3/d with strong piggery waste during summer in order not to exceed the reactor temperature higher than 35 degrees C.