Simultaneous biodegradation of organic (chlorophenols) and inorganic compounds from secondary sludge of pulp and paper mill by Eisenia fetida

Abstract

Present research communicates the role of Eisenia fetida in converting pulp and paper mill sludge into valuable products by removing the high concentration of different chlorophenols and metals present in the sludge. Pulp and paper mill sludge was toxic to Eisenia fetida and therefore, it was mixed with composted material in different ratio of experimental set up such as Set up: 1, (95:5), Set up: 2 (80:20) and Set up: 3 (50:50) on dry weight basis. We found very promising results by the application Eisenia fetida in the sludge. Eisenia fetida removed all the twelve different chlorophenols more than 95 % from the sludge which is declared as carcinogenic compounds by United States Environmental Protection Agency (US-EPA) in 90 days of incubation. Heavy metals concentration was decreased significantly during the incubation period whereas some metal concentration was also increased in the sludge due to mineralization. Carbon (C) and Nitrogen (N) were increased in the composted material, C:N ratio for Set 1 9:4 in Set 2 13:4 and Set 3 18:4 was observed which acts as soil conditioner. Whereas some other metals like (Ca, Mg, Na, K, Fe and Zn) was increased that are essential for the plant growth. There was great reduction in adsorbable organic halogen (AOX) 95 % and extractable organic halogen (EOX) 90 % as compare to control. Eisenia fetida also removed pentachlorophenol (PCP) from the sludge with artificially increased concentration about 100 mg/kg. By observing chlorophenols concentration, metals and carbon–nitrogen ratio, Eisenia fetida is acting as a potential candidate for the reclamation of industrial sludge. The result indicated that vermicomposting with Eisenia fetida is better option to manage the sludge or convert the sludge into nutrient-rich composted material in a short span of time.