Asha Srinivasan

Decolorization of dye wastewaters by biosorbents: a review.

Dye wastewater is one of the most difficult to treat. There has been exhaustive research on biosorption of dye wastewater. It is evolving as an attractive option to supplement conventional treatment processes. This paper examines various biosorbents such as fungi, bacteria, algae, chitosan and peat, which are capable of decolorizing dye wastewaters; discusses various mechanism involved, the effects of various factors influencing dye wastewater decolorization and reviews pretreatment methods for increasing the biosorption capacity of the adsorbents. The paper examines the mismatch between strong scientific progress in the field of biosorption and lack of commercialization of research.

Removal of oil by walnut shell media

Studies were conducted to evaluate the oil sorption capacities of walnut shell media. Sorption capacity is the weight of oil picked up by unit weight of a sorbent. Initial oil pick-up by walnut shell media on pure oil and oil on aqueous medium was evaluated. Batch kinetic studies were conducted to evaluate the equilibrium time required by walnut shell media for sorbing oil. For pure oil medium, sorption capacities of 0.30g/g, 0.51g/g and 0.58g/g were obtained for standard mineral oil, vegetable oil and DoALL Bright-Edge oil, respectively. The results showed sorption capacities of 0.56g/g, 0.58g/g and 0.74g/g for standard mineral oil, vegetable oil and DoALL Bright-Edge oil, respectively, for oil on aqueous medium. It was found that sorbed oil could be recovered from walnut shell media by applying pressure. The study showed that walnut shell media can be used as a sorbent for oil removal.

Biological treatment processes for fish processing wastewater–A review

Water consumption in a fish-processing industry and high-strength wastewater from such an industry are of great concern world-wide. Liquid effluent regulations are becoming more stringent day by day. Biological treatment is the best option for such a wastewater. Anaerobic processes such as upflow anaerobic sludge blanket (UASB) reactor, anaerobic filter (AF) and anaerobic fluidized bed (AFB) reactor can achieve high (80-90%) organics removal and produce biogas. Aerobic processes such as activated sludge, rotating biological contactor, trickling filter and lagoons are also suitable for organics removal. Anaerobic digestion followed by an aerobic process is an optimal process option for fish processing wastewater treatment.

Oil removal from water using biomaterials

A batch study was conducted to evaluate efficiencies of four types of biomaterials to remove oil from water. The oils used in the study were standard mineral oil, vegetable oil and cutting oil. Two fungal biomasses of Mucor rouxii and Absidia coerulea along with chitosan and walnut shell media were the biomaterials used. The study was carried out with an initial oil concentration of 200mg/L for 6h. Non-viable M. rouxii biomass was found to be more effective than A. coerulea biomass in removing oil from water. The study demonstrated that the removal efficiencies by M. rouxii for these oils were in the 77-93% range at a pH of 5.0. The adsorption capacities for standard mineral oil, vegetable oil and cutting oil were 77.2, 92.5, and 84 mg/g of biomass, respectively. The adsorption capacities for various oils exhibited by M. rouxii biomass were less than those of chitosan and walnut shell media.

Oil removal from water by fungal biomass: a factorial design analysis.

A fractional factorial design analysis was conducted to screen the significant factors influencing removal of three emulsified oils from water, namely, standard mineral oil (SMO), canola oil (CO) and Bright-Edge 80 cutting oil using non-viable biomass of fungus Mucor rouxii rich with chitosan in its cell wall. Factors investigated were pH of the solution (3-9), temperature (5-30 degrees C), adsorbent dose (0.05-0.5 g), concentration of oil (50-350 mg/L) and rotational speed of the shaker (100-200 rpm). It was observed that pH of the solution was the most influencing parameter on the removal of all the three oils studied. Higher oil removal efficiencies (80-99%) were obtained at a pH of 3.0 by M. rouxii biomass for all the three oils studied. Temperature had an effect on SMO and Bright-Edge 80 removal while adsorbent dose was found to influence the removal of SMO. Average removals of SMO and Bright-Edge 80 were higher by 13% at a solution temperature of 30 degrees C compared to removals at 5 degrees C. Oil concentration had an effect on the removal of CO. The average removal of CO was found to be higher by approximately 15% at an initial oil concentration of 50mg/L than at 350 mg/L.

Perchlorate: Health Effects and Technologies for Its Removal from Water Resources

Perchlorate has been found in drinking water and surface waters in the United States and Canada. It is primarily associated with release from defense and military operations. Natural sources include certain fertilizers and potash ores. Although it is a strong oxidant, perchlorate is very persistent in the environment. At high concentrations perchlorate can affect the thyroid gland by inhibiting the uptake of iodine. A maximum contaminant level has not been set, while a guidance value of 6 ppb has been suggested by Health Canada. Perchlorate is measured in environmental samples primarily by ion chromatography. It can be removed from water by anion exchange or membrane filtration. Biological and chemical processes are also effective in removing this species from water.

Fungal Biosorption and Biosorbents

The common filamentous fungi can sorb heavy metals from aqueous solutions. Fungal biosorption largely depends on parameters such as pH, metal ion and biomass concentration, physical or chemical pretreatment of biomass, presence of various ligands in solution, and to a limited extent on temperature. The cell-wall fraction of biomass plays an important role in the sorption of heavy metals. The fungal biosorbents widely used for heavy metal removal are reviewed in this chapter, mainly focusing on their performance, pretreatment, regeneration/reuse, modeling of biosorption, their potential application and future. The potential of fungal biomass as sorbents has been established by the available data, and more research and development of the fungal biosorption technology is recommended. The mismatch between strong scientific progress in the field of biosorption and lack of commercialization of research is evident.

Microwave oxidation treatment of sewage sludge

Microwave-oxidation treatment of sewage sludge using various oxidants was studied. Two treatment schemes with a combination of hydrogen peroxide and ozone were examined: hydrogen peroxide and ozone were introduced into the sludge simultaneously, followed by microwave heating. The other involved the ozonation first, and then the resulting solution was subjected to microwave and hydrogen peroxide treatment. The set with ozonation followed by hydrogen peroxide plus microwave heating yielded higher soluble materials than those of the set with hydrogen peroxide plus ozone first and then microwave treatment. No settling was observed for all treatments in the batch operation, except ozone/microwave plus hydrogen peroxide set at 120°C. The pilot-scale continuous-flow 915 MHz microwave study has demonstrated that microwave-oxidation process is feasible for real-time industrial application. It would help in providing key data for the design of a full-scale system for treating sewage sludge and the formulation of operational protocols.

Coalescence/Filtration of an Oil-In-Water Emulsion in an Immobilized Mucor rouxii Biomass Bed

Breakdown mechanisms and flow characteristics involved in an immobilized M. rouxii biomass bed treating oil-in-water emulsion were investigated. The purpose of this research was to evaluate the applicability of the well-known Carman-Kozeny filtration equation to a 1000 mm immobilized M. rouxii biomass bed treating a standard mineral oil-in-water emulsion at six different flow rates (12, 16, 20, 24, 28, and 32 mL/min). The specific permeability coefficient, the Carman-Kozeny constant, and the shape factor of immobilized M. rouxii bed were found to be 2.135 × 10−8 m2, 5.03, and 1.13, respectively. The coalescence efficiency decreased with an increase in bed depth (from 15.9% at 200 mm to 4.0% at 1000 mm depth for a flow rate of 12 mL/min). Results indicated possible sequential occurrence of coalescence and filtration in the immobilized M. rouxii biomass bed.

Effects of acidifying reagents on microwave treatment of dairy manure

Dairy manure, acidified using organic acids (acetic, oxalic, and citric acid) were treated with microwave enhanced advanced oxidation process (MW/H2O2-AOP). The effect of a mixture of oxalic acid and commonly used mineral acids (sulfuric and hydrochloric acid) on MW/H2O2-AOP was also examined. Substantial amounts of phosphorus were released under MW/H2O2-AOP, regardless of organic acid or mineral acid used. All three organic acids were good acidifying reagents; however, only oxalic acid could remove free calcium ion in the solution, and improve settleability of dairy manure. The MW/H2O2-AOP and calcium removal process could be combined into a single-stage process, which could release phosphate, solubilize solids and remove calcium from dairy manure at the same time. A mixture of oxalic acid and mineral acid produced the maximum volume of clear supernatant and had an ideal molar ratio of calcium to magnesium for effective struvite (magnesium ammonium phosphate) crystallization process. A single-stage MW/H2O2-AOP would simplify the process and reduce mineral acid consumption compared to a two-stage operation. The results of a pilot scale study demonstrate that MW/H2O2-AOP is effective in treating manure and recovering resource from dairy farms.