Treatment of unhairing effluents by activated sludge system

Abstract

The unhairing step in leather manufacture generates a highly hazardous and alkaline wastewater. This article reports the evaluation of an activated sludge system for the treatment of unhairing wastewater and effluent detoxification, assessed by seed germination tests.The activated sludge system reactor was fed for 112 days with diluted unhairing effluent; the operation strategy included increasing the organic loading rate (OLR) from 0.7 to 1.6 g chemical oxygen demand (COD) L 21 d 21 . COD and suspended solids (SS) removal efficiencies were up to 85 and 80%, respectively, for an OLR lower than 1.4 g COD L 21 d 21 . Sulphide removal efficiency was 90%, as sulphide was oxidized to other species such as sulphate. The biological oxidation of thiosulphates into tetrathionates was also investigated.The effect of untreated and treated unhairing wastewater on seed germination of maize, sorghum, and wheat was examined. Treatment decreased the phytotoxicity of the wastewater. Indeed, germination was inhibited when effluent dilution was lower than 90% of untreated wastewater, whereas a positive effect of treated wastewater was noticed.Phytotoxicity assays showed that biological treatment of unhairing wastewater contributed to a decrease in toxicity of the effluent. 2010 American Institute of Chemical Engineers Environ Prog, 30: 337-346, 2011

Microbial diversity in tanning wastewaters treatment reactors

“…In previous work, we compared the performances of aerobic tank reactors for treatment of unhairing wastewater . As the structure and dynamics of the microbial community in the biological processes applied to tannery wastewater are poorly understood, we report the results of an investigation into the structure and dynamics of key functional groups in the microbial communities of activated sludge and endogenous biomass reactors.…”

Detoxification Assays of Tunisian Tannery Wastewater under Nonsterile Conditions Using the Filamentous Fungus Aspergillus niger

“…Although no characterization of organic pollutants was carried out in this study, previous studies reported the profile of organic and inorganic compounds in tannery effluents. According to Mlaik et al [20], UE contains high organic load, lime, and sodium sulfide since they are used during liming-unhairing operation. Also, Mlaik et al [58] pointed to the presence of many hydrocarbons, including saturated (C16:0, C18:0) and unsaturated fatty acid methyl esters as well as long- and short-chain alkenes in the UE.…”

“…For all samples, seedling phytotoxicity was measured using different dilutions of raw and treated effluent samples (10, 20, 50, and 100%). Dilutions were chosen based on some literature studies, especially those of Mlaik et al [20], and also on our preliminary assays in which we found that 30% was nearly the same as 20% and 40% gives very similar results to those of 50%. For proportions from 60% to 90%, there was a high inhibition level of the germination seeds; that's why these proportions were not mentioned.…”

“…On the other hand, the toxicity of tannery effluents was reported in several studies [14–16]. Most of these studies revealed that the effects of tannery wastewater are devastating not only to humans [17] but also to birds [18], fish [19], plants [20], amphibians [21], and algae and daphnia [22, 23]. Furthermore, toxicity of tannery effluents to mice was investigated [16, 24, 25].…”

Combination of air stripping and biological processes for landfill leachate treatment

“…Therefore, the biological approach that combines anaerobic and aerobic processes can be advisable as a handy tool for removing organics from LFL pretreated with air stripping method. Among the main aerobic treatments, we can highlight activated sludge [22], biofilters [23] and rotating biological contactors [24].…”