Вестник МГТУ. 2018, том 21, № 1.

Васильева Ж. В. и др. Получение биофлокулянтов из биомассы активного ила… 80 УДК 628.316:628.336:577.11 Zh. V. Vasilieva, E. Yu. Moshnyatckaya Extraction of bioflocculants from activated sludge and their application to wastewater treatment Extracellular polymeric substances (EPS) – biopolymers produced by the microorganisms – are effective flocculants of wastewater pollution and lack the shortcomings of traditional coagulants and flocculants, which can pose direct threat to health and human life, as well as to the sustainable existence of aquatic and terrestrial ecosystems. EPS do not form secondary contamination of their degradation intermediates, are biodegradable and eco-friendly. Industrial production of bacterial EPS is associated with high cost of growing specific microbial biomass and the functioning of technologies for the synthesis of microbial products. At the same time, there is an underused resource of excess activated sludge, which can be used as cheap substrate for producing bioflocculants and a possible measure to reduce costs. The conducted researches have shown the prospects of extracting EPS from excess activated sludge for their subsequent use as wastewater treatment bioflocculants. EPS extraction has been conducted using three methods: combination of centrifugation processes, extraction using the aqueous solution of disodium ethylenediaminetetraacetic acid, and precipitation with isopropyl alcohol (the EDTA method); combination of centrifugation, extraction with (NH 2 ) 2 CO, precipitation and ethanol reprecipitation (the (NH 2 ) 2 CO method); combination of activated sludge ultrasonic treatment, centrifugation, extraction with glacial acetic acid, and precipitation with acetone (the CH 3 COOH method). The research has shown that the extraction method affects not only the efficiency of EPS extraction, but also the possibility of EPS application for the purification of certain types of sewage. The (NH 2 ) 2 CO method has shown the best extraction efficiency, but at the same time EPSs produced have not be able to perform fish processing wastewater treatment. The EDTA and CH 3 COOH methods are more preferable for producing efficient bioflocculants for fish processing wastewater treatment. The use of EPS obtained by the EDTA method has resulted in the significant reduction of total suspended solids and optical density; EPS produced by the CH 3 COOH method have reduced the content of dissolved solids and the optical density. According to the conducted research EPS produced from surplus sludge with the EDTA and CH 3 COOH methods have good flocculation and are harmless for humans and the environment, and thus may be a potential substitute for traditional synthetic flocculants and could be used in the treatment of fish processing plants wastewaters. Key words: extracellular polymeric substances (EPS), bioflocculants, activated sludge, wastewater treatment. Introduction Coagulation and flocculation have received a wide spread in the field of industrial wastewater treatment, this is due to their following advantages: the possibility of treating wastewater to the required values from virtually all types of contaminants that differ in both chemical and phase-dispersed composition; technological flexibility of cleaning systems when changing the parameters of incoming water; rational size of treatment facilities, no need for large production areas, etc. However, the experience of using traditional synthetic flocculants and coagulants in wastewater treatment has revealed a number of their significant shortcomings: the formation of neurotoxic and carcinogenic acrylamide monomers of flocculants as well as high residual content of heavy metal ions (Al 3+ , Fe 3+ ) of coagulants in the water. The links have been revealed between the existence of Al in the drinking water and human neurological disorders such as dialysis encephalopathy [1]. Along with this, the evidence of links in case of Alzheimer's disease caused by aluminum salts have been determined [2]. The arguments associated with the potential danger of effects of acrylamide monomers on the environment and human health have been summarized [3; 4]. These shortcomings do not limit or exclude the use of synthetic flocculants and coagulants, which can pose a direct threat to the health and human life, and a threat to the sustainable existence of aquatic and terrestrial ecosystems. On the other hand, other agents of wastewater treatment have become known in recent years – extracellular polymeric substances (EPS). Extracellular polymeric substances, or as it is called, microbial bioflocculants, do not form a secondary contamination of their degradation intermediates; they are biodegradable and eco-friendly [5–8]. EPS are functionally flocculating agents that promote agglomeration of dispersion and colloidal particles of wastewater into well precipitating complexes; therefore they are capable to achieve a significant reduction of pollutants concentrations contained in the wastewater [9; 10]. The production of microbial EPS in Russia does not meet the requirements of the increasing demand of various industries, medicine and agriculture in these biopolymers [11]. Meanwhile, industrial production of bacterial EPS is associated with the high cost of growing specific microbial biomass, the functioning of technologies for the synthesis of microbial products. At the same time, there is an obvious resource for obtaining significant amounts of microorganism biomass and products of their synthesis. Biological treatment facilities daily produce a significant amount of