Bio-electrochemical Denitrification -A review

Discharge of nitrogen components into the environment can be a cause of serious problems such as eutrophication of rivers and deterioration of water sources, as well as hazard for human and animal health. Ammonia (NH3) and nitrate (NO3-) are the most problematic nitrogen compounds in water and wastewaters. Nitrification is a common way to eliminate ammonia in municipal and industrial wastewater, which during this process ammonia oxidizes to nitrate. Nitrate removal from these types of wastewaters is an inevitable step in the treatment. Biological nitrate removal is a suitable but slow method to remove nitrate from water and wastewater. Therefore, in treatment plants, some abiotic methods have been commonly applied. However, these methods have indicated some drawbacks such as highly concentrated brine solution, which compels complexity for further treatment or disposal. Consequently, efforts have focused on speeding up microbial denitrification techniques, and different methods have been investigated in the last two decades. Among them bio–electrochemical reactors (BERs) which are equipped with immobilized autohydrogenotrophic microorganisms on cathode showed good efficiency for implementation of denitrification for any nitrate–contaminated water stream. This article reviews the diversity of nitrate source, various designs, and aspects of BERs. In addition, it discusses the variation of pH, carbon source, electric current (EC) and hydraulic retention time (HRT) as some main effective parameters on denitrification rates, and different configurations of BERs

Effect Of Fenton Process (H2O2 / Fe2+) On Removal Of Linear Alkylbenzene Sulfonate Using Central Composite

This study investigates the degradation of Linear Alkylbenzene Sulfonate (LAS) in aqueous solution using Fenton’s process in a batch reactor (at pH = 3 and 25°C). Experiments were carried out to survey the effects of the amounts of ferrous sulfate (FeSO4.7H2O) and hydrogen peroxide (H2O2) on the LAS and COD removal. Central composite design and response surface methods were used to optimize the Fenton oxidation process through examination of three independent operating variables namely oxidant dose (H2O2), catalyst dose (Fe+2) and reaction time., hydrogen peroxide dose ranging from 150 to 750 mg /L and Fe+2 concentration in the range of 10 –130 mg /L were selected to be examined at different reaction times between 20 and 80 minutes. Models were developed and results shows that the oxidation capacities of H2O2 /Fe+2 were highly dependent on the concentration of H2O2 and Fe+2. Satisfactory decay rates of LAS to lock up biodegradable concentration level were obtained, and in the case for oxidation of 200 mg /L LAS, the optimum values were achieved at 600 and 130 mg/L for H2O2 and Fe+2, respectively