Investigation of endogenous biomass efficiency in the treatment of unhairing effluents from the tanning industry

• Published in: Environmental technology Vol. 30; no. 9; pp. 911 - 919
• Main Authors: Mlaik, Najwa, Bouzid, Jalel, Gharsallah, Neji, Belbahri, Lassad, Woodward, Steve, Mechichi, Tahar
• Format: Journal Article
• Language: English
• Published: Abingdon Routledge 01-08-2009; Taylor & Francis
• Subjects: Alkalinity; Applied sciences; Biodegradability; Biodegradation, Environmental; biological treatment; Biomass; Bioreactors - microbiology; Chemical engineering; Crack opening displacement; Culture; Economics; Effluents; endogenous biomass; Environmental impact; Exact sciences and technology; General purification processes; General treatment and storage processes; Germination; germination index; Hair; Hair - chemistry; Hides; Industrial Waste - prevention & control; Minerals; Optimization; Plants (organisms); Pollution; Reactors; Seeds; Sewage - microbiology; Sulfates; Sulfides; Sulfides - isolation & purification; Sulfides - metabolism; Sulfur; sulphide oxidation; Sulphur; Tanning; Tanning industry; Thiosulfates; Toxic; Toxicity; Toxicology; Transformations; Unhairing; unhairing effluent; Waste water; Wastes; Wastewaters; Water Microbiology; Water Pollutants, Chemical - isolation & purification; Water Pollutants, Chemical - metabolism; Water Purification - methods; Water treatment and pollution; British Isles; Biodegradability; Toxicity; Waste treatment; endogenous biomass; Detoxification; sulphide oxidation; Biomass; germination index; Sulfates; tanning industry; Waste water; Dilution; unhairing effluent; Batchwise; Organic loading; Chemical oxygen demand; Environment impact; Leather industry; Water quality; pH; Oxidation; Biological treatment; Reactor; Continuous system
• ISSN: 0959-3330; 1479-487X
• DOI: 10.1080/09593330902971261

The tanning industry is of great economic importance worldwide; however, the potential environmental impact of tanning is significant. An important component in tanning is the removal of hair from the hide (unhairing), a process which generates considerable amounts of toxic effluent characterized by a high concentration of sulphur, rich mineral compounds, a high alkalinity and a high organic load. The purpose of the work described here was to evaluate the biodegradability of the unhairing wastewater by endogenous biomass in batch culture and continuous systems. The detoxification of the effluent was assessed by seed germination tests. The batch culture experiments showed that variations in COD, temperature and pH significantly affected the endogenous biomass growth and activity. The optimal treatment condition corresponded to an initial COD of 6 g/L, pH of 7 and 30 °C. Under continuous culture conditions, the reactor was fed for 48 days with the unhairing effluent. The optimal COD removal efficiency was 85.5%. During treatment, a transformation of sulphides into thiosulphates and then sulphates was also observed. The effect of untreated and treated unhairing wastewater on seed germination of different plant species was studied. The data suggested that treatment decreased the wastewater toxicity. Indeed, germination was inhibited when the effluent dilution was lower than 20% and 10% for treated and untreated wastewater, respectively.