a b s t r a c tCassava (Manihot esculenta) being rich in starch is one of the critical industries in the agro-industrial sector. The present study aims to do a comparative study on the treatment of cassava wastewater using biological and eco-friendly treatment approaches consisting of native bacterial species and fungal consortium in free, immobilized and biofilm batch mode. Studies were performed using the mixed culture of native bacteria, and the results were compared with that of a mixed fungal consortium of Trichoderma harzianum and Trichoderma viride which were known for its cyanide degrading efficiency and reducing COD burden. Cyanide and COD were two critical pollutants for the study. The effect of treatment time on cyanide and COD removal was investigated without adding any buffer to the wastewater. The maximum cyanide and COD removal efficiency for wastewater by using mixed native bacterial were 41.12% and 53.07% respectively. The removal efficiency by mixed bacterial culture was not too high owing to the low pH of cassava wastewater. Even in the low pH of cassava wastewater the maximum cyanide and COD removal efficiency using fungal consortium were 63.77% and 74.3% respectively. The growth pattern of fungal consortium reveals that six days treatment period showed maximum biomass of 3.721 g/L of dry weight. Thus, six days of treatment of fungal consortium can be used for the treatment of cassava wastewater. Furthermore, the optimized value of temperature and inoculums dosage for fungal consortium was found to be 30°C and 4% (v/v) of wastewater. Under optimized condition free, immobilized and biofilm batch reactors were setup. Biofilm batch reactor gave COD removal efficiency of 88% followed by suspension with 83.5% and least in an immobilized batch reactor with 76.5%. Cyanide removal efficiencies of 98.19%, 77%, and 87% were obtained in a biofilm, suspension and immobilized system respectively. The experimental results showed that final pH after treatment in all three systems was in dischargeable limits. The study revealed that the biofilm batch reactor which gave the highest removal efficiency could be considered as the best method for treatment of cassava wastewater.
The presence of surfactants typically found in laundry discharge poses a serious threat to aquatic niche when let out in open water bodies. In the present study, activated carbon produced from a novel source, Colocasia esculenta has been suggested as adsorbent to trap turbid colloids present in the surfactant wastewater. A synthetic wastewater was prepared by spiking kaolin in aqueous solution for different concentrations and the adsorption studies have been conducted. The carbon has been modified into carbon-sodium alginate bead complex and the operating parameters like pH, adsorbent dosage and its contact time under different concentrations have been optimized. The maximum equilibrium uptake capacity of 2.067 mg/g was achieved at 60 min with adsorbent dosage of 1.5 g conducted in neutral pH. Langmuir and Freundlich models were used to predict the reaction kinetics and it was hypothesized that multi-layer physisorption is predominant at higher concentrations. Strychnos potatorum, a common household bio-coagulant has been suggested in the continuous mode process designed specifically to treat the discharge form laundry. The total dissolved solids present in the wastewater has been reduced from 168 ppm to 12 ppm with a total reduction of 92.86%, while the turbidity has been reduced from an average 132 NTU to 10 NTU.
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