Showing papers on "Hydraulic retention time published in 2014"

A two-stage microbial fuel cell and anaerobic fluidized bed membrane bioreactor (MFC-AFMBR) system for effective domestic wastewater treatment.

Abstract: Microbial fuel cells (MFCs) are a promising technology for energy-efficient domestic wastewater treatment, but the effluent quality has typically not been sufficient for discharge without further treatment. A two-stage laboratory-scale combined treatment process, consisting of microbial fuel cells and an anaerobic fluidized bed membrane bioreactor (MFC-AFMBR), was examined here to produce high quality effluent with minimal energy demands. The combined system was operated continuously for 50 days at room temperature (∼25 °C) with domestic wastewater having a total chemical oxygen demand (tCOD) of 210 ± 11 mg/L. At a combined hydraulic retention time (HRT) for both processes of 9 h, the effluent tCOD was reduced to 16 ± 3 mg/L (92.5% removal), and there was nearly complete removal of total suspended solids (TSS; from 45 ± 10 mg/L to <1 mg/L). The AFMBR was operated at a constant high permeate flux of 16 L/m(2)/h over 50 days, without the need or use of any membrane cleaning or backwashing. Total electrical energy required for the operation of the MFC-AFMBR system was 0.0186 kWh/m(3), which was slightly less than the electrical energy produced by the MFCs (0.0197 kWh/m(3)). The energy in the methane produced in the AFMBR was comparatively negligible (0.005 kWh/m(3)). These results show that a combined MFC-AFMBR system could be used to effectively treat domestic primary effluent at ambient temperatures, producing high effluent quality with low energy requirements.

Characteristics, process parameters, and inner components of anaerobic bioreactors

Abstract: The anaerobic bioreactor applies the principles of biotechnology and microbiology, and nowadays it has been used widely in the wastewater treatment plants due to their high efficiency, low energy use, and green energy generation. Advantages and disadvantages of anaerobic process were shown, and three main characteristics of anaerobic bioreactor (AB), namely, inhomogeneous system, time instability, and space instability were also discussed in this work. For high efficiency of wastewater treatment, the process parameters of anaerobic digestion, such as temperature, pH, Hydraulic retention time (HRT), Organic Loading Rate (OLR), and sludge retention time (SRT) were introduced to take into account the optimum conditions for living, growth, and multiplication of bacteria. The inner components, which can improve SRT, and even enhance mass transfer, were also explained and have been divided into transverse inner components, longitudinal inner components, and biofilm-packing material. At last, the newly developed special inner components were discussed and found more efficient and productive.

Effects of Temperature and Hydraulic Retention Time on Acetotrophic Pathways and Performance in High-Rate Sludge Digestion

Abstract: High-rate anaerobic digestion of organic solids requires rapid hydrolysis and enhanced methanogenic growth rates, which can be achieved through elevated temperature (>55 °C) at short hydraulic retention times (HRT) This study assesses the effect of temperatures between 55 °C and 65 °C and HRTs between 2 and 4 days on process performance, microbial community structure, microbial capability, and acetotrophic pathways in thermophilic anaerobic reactors Increasing the temperature did not enhance volatile solids (VS) destruction above the base value of 37% achieved at 55 °C and 4 days HRT Stable isotopic signatures (δ13C) revealed that elevated temperature promoted syntrophic acetate oxidation, which accounted for 60% of the methane formation at 55 °C, and increasing substantially to 100% at 65 °C The acetate consumption capacity dropped with increasing temperature (from 069-081 gCOD gVS(-1) d(-1) at 55 °C to 021-035 gCOD gVS(-1) d(-1) at 65 °C), based on specific activity testing of reactor contents Community analysis using 16S rRNA pyrosequencing revealed the dominance of Methanosarcina at 55-60 °C However, a further increase to 65 °C resulted in loss of Methanosarcina, with an accumulation of organic acids and reduced methane production Similar issues were observed when reducing the HRT to 2 days, indicating that temperature 3 days are critical to operate these systems stably

Performance of SBR for the treatment of textile dye wastewater: Optimization and kinetic studies

Abstract: In this work, sequential batch reactor (SBR) was employed for the treatment of textile dye wastewater. The performance of four white rot fungi (WRF) viz. Coriolus versicolor, Pleurotus floridanus, Ganoderma lucidum and Trametes pubescens was evaluated in pure and mixed combinations in terms of decolorization. From the results it was found that the combination of Pleurotus floridanus, Ganoderma lucidum and Trametes pubescens was best and they were used in the SBR. The process parameters like air flow rate, sludge retention time (SRT) and cycle period were optimized using response surface methodology (RSM). At these optimized conditions, treatment of textile dye wastewater was carried out at various initial dye wastewater concentration and hydraulic retention time. The performance of SBR was analyzed in terms of decolorization, COD reduction and sludge volume index (SVI). From the results it was found that a maximum decolorization and COD reduction of 71.3% and 79.4%, respectively, was achieved in the SBR at an organic loading rate of 0.165 KgCOD/m3 d. The sludge volume index (SVI) was found to be low in the range of 90–103 mL/g. The kinetic study was carried out using a first order based model and the degradation follows the first order system.