Experimental studies on the impact of porous bed-induced solar evaporation (PBISE) and thermal degradation of the solid content of the distillery effluent using cocopeat- A sustainable approach

Abstract

The distillery industries are a highly water-intensive unit that discharges a higher volume of effluent while producing alcohol. Various treatment methods were adopted for the treatment of the effluent to bring down the effluent to the discharge standards. The available treatment methods are highly energy intensive, besides producing a sludge at the end of the treatment process, which needs further treatment or a disposal technique. The objective of the present work is to arrive at a sustainable method of evaporating the distillery effluent using a solar still in presence of cocopeat as bed material for evaporation and to study the feasibility of the thermal decomposition of the sludge obtained from the still. This study compares the drying rate of distillery effluent in presence of cocopeat as a bed material with that of the distillery effluent without bed material at isothermal conditions (60–100 °C). Experiments are conducted in an open atmosphere using solar still to study the effect of bed material on the rate of evaporation of the effluent. Further, the distillate produced in the solar stills containing tap water(S1), distillery effluent(S2), and effluent with cocopeat as bed material (S3) were compared. The sludge obtained from the stills (S2 & S3) was checked for the feasibility of thermal decomposition. The constant rate drying period got extended up to a critical moisture content (CMC) of 35% in the presence of cocopeat, compared to that of 62% in the case of effluent alone at 100 °C. This emphasizes the use of cocopeat as bed material in solar still could enhance the evaporation rate of effluent. The distillate yield in S1, S2, and S3 were 4.49 L/m2/day, 4.94 L/m2/day, and 5.41 L/m2/day respectively. The S3 shows a higher production of distillate yield by 10% than S2, proving that the extended constant rate period enhanced the distillate production. The sludge obtained from S2 and S3 was thermally decomposed by a Thermogravimetric analyzer. The residual weight in the case of thermal decomposition of effluent solids (S2) was 25% whereas in the case of a mixture of cocopeat and effluent solids (S3) was reduced to 5%. The synergistic behavior of the thermal decomposition between the cocopeat and the effluent solids was observed from the thermogravimetric analysis of the sludge. Hence, the solid waste obtained from the still is also effectively managed by co-combustion.