P. Arulazhagan

Effect of alkaline and ozone pretreatment on sludge reduction potential of a membrane bioreactor treating high-strength domestic wastewater

AbstractThe wide application and utilization of the activated sludge process has resulted in the production of excess sludge, posing a serious disposal problem. Many efforts have been dedicated to reduce the excess sludge by treatments such as digestion and dewatering. In this study, an aerobic submerged membrane bioreactor (MBR) was used to study the effect of alkaline and ozone pretreatment on the efficiency of sludge reduction. For this purpose, two MBRs were fabricated. Among the two MBRs, one acted as a control reactor (CMBR) and the other acted as an experimental reactor (EMBR). The MBRs were operated with mixed liquor suspended solids (MLSS) concentrations in the range of 7,000–7,200 mg/L for a period of 120 d. In the EMBR, part of the MLSS was withdrawn at a ratio of 1.5% of Q and was pretreated by alkali-ozone. The sludge pretreatment was carried out at pH 11 and an ozone dosage of 0.09 gO3/g MLSS. During the pretreatment, 40% COD solubilization and 30% suspended solid reduction were observed. Th...

Electricity generation from retting wastewater consisting of recalcitrant compounds using continuous upflow microbial fuel cell

Recalcitrant compounds like phenol found in coconut husk retting effluent cause the deterioration of water quality when discharged from retting ponds into other water sources. Continuous upflow microbial fuel cell (MFC) was evaluated for treating retting wastewater at different loading rates to determine power generation, chemical oxygen demand (COD) consumption rate and phenol removal for a period of 270 days. A maximum power density of 254 mW/m2 was achieved during the treatment of retting wastewater (external resistance — 350Ω). COD removal of 70% was accomplished at a loading rate of 0.45 g COD/L reactor/day and phenol removal of 95% was obtained at a loading rate of 0.28 g phenol/L reactor/day. The power density exhibited an increasing pattern as the loading rate of MFC was increased from 0.45 to 2.69 g COD/L reactor/day. This study describes the treatment of retting wastewater employing continuous upflow MFC with 95% phenol removal. Therefore, MFC can be considered as an alternative for the efficient removal of phenol and current generation in retting wastewater.

Energy-efficient methane production from macroalgal biomass through chemo disperser liquefaction

In this study, an effort has been made to reduce the energy cost of liquefaction by coupling a mechanical disperser with a chemical (sodium tripolyphosphate). In terms of the cost and specific energy demand of liquefaction, the algal biomass disintegrated at 12,000rpm for 30min, and an STPP dosage of about 0.04g/gCOD was chosen as an optimal parameter. Chemo disperser liquefaction (CDL) was found to be energetically and economically sustainable in terms of liquefaction, methane production, and net profit (15%, 0.14gCOD/gCOD, and 4 USD/Ton of algal biomass) and preferable to disperser liquefaction (DL) (10%, 0.11 gCOD/gCOD, and -475 USD/Ton of algal biomass).

Anaerobic co-digestion of chemical- and ozone-pretreated sludge in hybrid upflow anaerobic sludge blanket reactor

AbstractThe present study is an attempt to anaerobically co-digest excess sludge from aerobic facility of dairy wastewater treatment plant in a hybrid upflow anaerobic sludge blanket reactor. The sludge was made amenable for anaerobic degradation using ozone and chemical pretreatment. The efficiency of the treatment at optimized condition (pH 11 and ozone dosage 0.06 gO3/g suspended solids) showed 68 and 61% of chemical oxygen demand solubilization and suspended solids reduction, respectively. Further, anaerobic co-digestion of pretreated sludge was evaluated in two lab-scale hybrid upflow anaerobic sludge blanket reactors, namely experimental (ER) and control reactors (CR), with 5.6 L working volume for a period of 310 d. Treatment of dairy wastewater at the highest applied organic loading rate of 16.78 kg chemical oxygen demand/m3 d, the biogas production increased in ER reactor (18.8 L/d) with the introduction of pretreated sludge than in CR reactor (17.9 L/d). The performance of ER reactor is not infl...

Synergistic impact of sonic-tenside on biomass disintegration potential: Acidogenic and methane potential studies, kinetics and cost analytics

An exploration into the symbiotic impact of sonic-tenside (SDBS - sodium dodecyl benzene sulfonate) on biomass disintegration potential and to reduce the energy consumption was studied. At optimized condition (specific energy input 9600 kJ/kg TS; SDBS dosage 0.07 g/g SS), higher percentage of biomass lysis and solids reduction (23.9% and 19.8%) was obtained in blended sonic-tenside disintegration (STD), than sonic disintegration (SD) (17.6% and 9.8%). The bioacidogenic potential (BAP) assay in terms of volatile fatty acids (VFA) production (722 mg/L) was found to be higher for STD, in comparison to SD (350 mg/L). The impact of STD on anaerobic digestion was evident from its methane yield (0.239 g/g COD), higher than SD (0.182 g/g COD). A monetary evaluation of the present study provides a net gain of 2 USD/ton for STD, indicating the profitability of the technique.

HC-0B-01: Biodegradation of Hydrocarbons by Extremophiles

Polycyclic aromatic hydrocarbons (PAHs) present in the petroleum wastewater are ubiquitous environmental pollutants. They are generated from both natural and anthropogenic processes, and pose a serious concern on the health of aquatic life and human beings through bioaccumulation. PAHs are known to be cytotoxic, mutagenic and carcinogenic. They persist in the environment due to their hydrophobic nature and are difficult to treat using chemical methods. This chapter details the biodegradation of PAHs under extremophilic condition. Bacteria, fungi and algae are reported to be used in the treatment of PAHs. Extremophilic conditions such as acidophilic (pH 1–5), alkaliphilic (pH > 9) halophilic (>3 % salt), thermophilic (temperature > 50 °C), psycrophilic (temperature 38 MPa) and xerophilic (aw 0.60–aw 0.90) conditions. Collection of samples, isolation of extremophilic micro-organism, mineralization of hydrocarbons and identification of microbes using molecular techniques are detailed. Despite the microbial ability to degrade petroleum hydrocarbons, there are factors such as temperature, pH and nutrients that influence the degradation of hydrocarbons. Information on mechanisms and pathways for petroleum hydrocarbon degradation under extreme conditions is scarcely known and recently few studies reported on enzymes, genes and metabolism of hydrocarbons. Microbial cell interaction with petroleum hydrocarbons are also detailed in this chapter. Extremophiles play a vital role in the degradation of petroleum hydrocarbons and in the treatment of refinery wastewater.