Comparative evaluation of the coagulation methods effectiveness in the extraction of biologically active components from highly concentrated effluents

Abstract

A characteristic feature of highly concentrated effluents is the presence of valuable components - biologically active substances, which are secondary raw materials. The effectiveness of physico-chemical coagulation and electrocoagulation methods in relation to highly concentrated wastewater from a poultry processing enterprise, as well as the prevention of the secondary pollution of the effluent supplied to biological treatment, were analyzed in the work. The objects of the study included poultry stock (suspended solids 1770.0 mg / dm3, dry residue 1920.0 mg / dm3, chemical oxygen demand (COD) 1769.0 mg O2 / dm3), iron (III) FeCl3 chloride, iron soluble electrodes as the coagulant. The objectives of study involved determination of wastewater treatment effectiveness by the studied methods (physico-chemical coagulation and electrocoagulation) with the priority indicators changing: suspended solids, dry residue, chemical consumption of oxygen, iron, chlorides, and the precipitated residue mass. As a result of testing of highly concentrated effluents with a COD index of at least 1700.0 mg O2 / dm3, it was found out that during physico-chemical coagulation with FeCl3 at a concentration of 0.75 g / dm3, the content of priority indicators decreased by no less than 60%, while the effectiveness of electrocoagulation in relation to reducing the concentration of priority indicators was at least 70%. The content of iron compounds in wastewater with the application of electrochemical coagulation was 2.08 mg / dm3, which is 34% lower than after treatment of the effluent with iron (III) chloride FeCl3 at a concentration of 0.75 g / dm3. The chloride concentration did not change. As a result of the treatment of the effluent during the coagulation of (III) FeCl3, the secondary contamination of the treated effluent and the isolated products with iron and chlorides took place. This aspect may adversely affect the subsequent biological wastewater treatment, as well as lead to a decrease in the quality of the isolated product and its use limitation. Electrocoagulation is a more preferred way of isolating valuable components in relation to physico-chemical coagulation.