Treatment and textile liquid waste

Abstract

Untreated or poorly treated effluent from textile industries is severely polluting the water courses of Bangladesh. Regular operation of well designed effluent treatment plant is necessary to reduce the pollution problem of Bangladesh. Lack of information on treatment efficiencies of different treatment options causes hindrance for the designers to select appropriate treatment units. This study represents an attempt to evaluate the efficiencies of two most widely used treatment methods. physicochemical treatment and physicochemical treatment followed by biological treatment method. The study also tried to identify simple and cost effective treatment method for the treatment of textile liquid waste. Investigations were made to evaluate the characteristics of textile liquid waste through literature review and laboratory tests. Textile liquid waste contains high biochemical oxygen demand and total suspended solids which can severely pollute the nearby water courses if discharged without proper treatment. High color and turbidity presence in the discharged effluent affect of the image of the industry. National effluent discharge standard for textile industries were reviewed to determine the extent of treatment required for textile liquid waste. Some serious limitations exist in the national effluent discharge standard for textile industries and needs to be fixed as soon as possible. Raw liquid waste was collected from a textile industry and physico-chemical and biological treatment processes were applied in the laboratory by varying different design parameters such as coagulant. dose. aeration time. Chemical coagulation with alum was used for physico-chemical treatment and sequencing batch reactor (SBR) unit was used for biological treatment. Treatment efficiencies were determined using post treatment pollutant concentration and were represented as percent of raw concentration of pollutant. BODs. COD. TDS, TSS, color and turbidity was taken as indicators in the assessment of treatment efficiencies of diffl1rent treatment options. Only physicochemical treatment is not adequate and subsequent biological treaLment is necessary for the treatment of textile liquid waste. Chemical coagulation can remove TSS up to 43 percent, COD up to 55 percent and BOD up to 3 j percent of raw wastewaLer concenLration. Il1lroduction of sequencing batch reactor treatment improves the removal of TDS up to 17 percent. TSS up to 15 percent, COD up to 23 percent and BODs up Lo54 percent. 70 percenL color can be removed by chemical coagulation. A comparative study between conventional activated sludge process and sequencIng batch reactor (SBR) process was carried out. The study focused in the area requirement, treatment efficiencies and operational cost aspects of those Lwo processes. The study result showed that the SBR process is more economical than activated sludge process as treatment efficiencies and operational cosL of the two units are approximately identical but area requirement in SBR system is less than that of activated sludge process.