Treatment and remediation of a wastewater lagoon using microelectrolysis and modified DAT/IAT methods

To examine treatment and remediation of a wastewater lagoon with poor biodegradability, a typical wastewater lagoon in Tianjin, China, was treated and remedied using microelectrolysis and modified demand aeration tank （DAT）/intermittent aeration tank （IAT） methods. After pretreatment by microelectrolysis, the removal efficiency of chemical oxygen demand （COD） was up to 64.6% and the ratio of BOC/COD in the effluent increased from 0.013 to 0.609. The removal rates of CODcr and NH4＋-N were affected by sludge backflow rate, mixed liquor suspended solids （MLSS）, and hydraulic retention time （HRT） in the modified DAT/IAT reactor. The highest removal rates of CODcr and NH4＋-N were up to 78.9% and 62.6%, respectively, when the sludge backflow rate was 38.0 mL/min, the total HRT was 8.0 hr and MLSS was 4088.0 mg/L. In this case, some protozoa and metazoa were observed in activated sludge and biofilm carriers. Most of chrominance was removed by microelectrolysis treatment, while the modified DAT/IAT methods were more effective for CODcr and NH4＋-N removal.

Enhancing the biological hydrogen production in a novel way of using co-substrates

Microbial electrolysis cell(MEC)is a potential technology to meet the increasing interest in finding new sources of energy that will not harm the environment.MEC is an alternative energy conversion technology for the production of biofuels.It is possible to produce hydrogen by fermenting biogenous wastes with hydrogen-producing bacteria.This study investigated the biohydrogen production from co-substrates using electrogenic bacteria such as Escherichia coli,Salmonella bongori,and Shewanella oneidensis in pure culture and as a co-culture,which has the potential to be used as co-substrate in MECs.Briefly,150 mL working-volume reactors were constructed for batch biohydrogen production.The hydrogen production rate(HPR)from the co-substrate was maximum at a ratio of 75:25 g/L with a co-culture of 2.35 mL/(L h).Fabricated a single-chamber membrane-free microelectrolysis cell to evaluate the power density,current density,voltage,HPR,chemical oxygen demand(COD)removal efficiency and Columbic efficiency.Scanning electron microscope(SEM)imaging confirmed the binding of electrogenic bacteria to anode and cathode.The efficiency of electrical conductivity of MEC was analyzed by three different electrodes,namely,nickel,copper and aluminum.The HPR was high using nickel when compared to the other two electrodes.The HPR of a single chamber using a nickel electrode was 2.8 HPR ml/L H_(2) d^(−1) and provided a power density of 17.7 mW/m^(2) at pH 7.This study suggests that the nickel cathode in a single chamber could be a promising sustainable source for stable power generation.

Mechanism and kinetics of 2-chlorophenol degradation in drinking water by photo-electrochemical synergic effect

The synergic effect mechanism of photo-electrochemical oxidation is investigated in detail through reaction products and kinetics analysis in a photo-electric integral reactor with 2-chlorophenol (2-CP) as the model pollutant. A kinetics model is constructed for the combinatorial photo-electrochemical (CPE) degradation. A remarkable synergetic effect, which can significantly enhance the mineralization rate of the CPE process, is verified by the comparison of apparent kinetic constants. In the CPE process, complemental effects with multi-level and multi-pathway for pollutants degradation under our experimental conditions are speculated. It is proved that the degradation pathways are not only the simple summation of that of photolysis and electrolysis, but the formation of synergic effect through combination of several new acting approaches. The degradation efficiency is enhanced considerably by three factors, control of electrode poisoning by the UV irradiation, control of excitation and reaction trend of pollutants molecules by the UV irradiation, and control of activation effect and transfer trend by the oriented direct current (DC) electric field. An advanced oxidation system is set up through manifold of free radicals chain reactions in the CPE reactions, so that the aqueous organics can be mineralized fast and completely. It is proven by the kinetics analysis that the mineralization of organic pollutants is mainly attributed to the generation of very active hydroxyl radicals (OH@) in bulk solution from the CPE synergetic effect.