Вестник МГТУ. 2018, том 21, № 1.

Вестник МГТУ. 2018. Т. 21, № 1. С. 80–87. DOI: 10.21443/1560-9278-2018-21-1-80-87 81 excess activated sludge, which is a consortium of microorganisms of various systematic groups of micromycetes, yeasts, and bacteria, which in their turn are natural producers of exobiopolymers. At present, this resource is a large-scale waste and does not find suitable practical application. Thus, activated sludge can be used as a cheap substrate for the production of bioflocculants as a possible measure to reduce costs. In the scope of this work studies have been conducted that have shown the prospect of extracting EPS from excess activated sludge for their subsequent use as bioflocculants of wastewater treatment. In addition, until now there has been no report about treating fish processing wastewater using bioflocculants. Accordingly, EPS extraction from excess activated sludge and investigating the effects of bioflocculant extraction methods on the efficiency of fish processing wastewater treatment have been the aims of this study. Materials and methods Samples of excess activated sludge were collected from the wastewater treatment system at the JSC "Murmansk Bakery Complex" in the city of Murmansk, the Murmansk region, Russia. Activated sludge was collected from the aeration tank. The collected samples were transported to the laboratory within 2 hours after sampling at the temperature of 4 °C. Determination of hydro-chemical parameters of activated sludge was carried out in accordance with the methodics 1 . The basic properties of the sludge water are listed in Table 1. Table 1. Characteristics of activated sludge Таблица 1. Показатели активного ила Suspended Solids, g/l Sludge Volume Index Settled Sludge Volume, ml/l pH Temperature, °C Activated sludge samples 2.3 65 150 7.1 8.5 Extraction of EPS has been conducted using three different methods: – the EDTA method – a combination of centrifugation processes, extraction using aqueous solution of disodium ethylenediaminetetraacetic acid (EDTA), and precipitation of isopropyl alcohol [12]; – the (NH 2 ) 2 CO method – a combination of centrifugation, extraction with (NH 2 ) 2 CO, precipitation and ethanol reprecipitation [13]; – the CH 3 COOH method – a combination of ultrasonic cavitation treatment of activated sludge, centrifugation, extraction with glacial acetic acid, and precipitation with acetone [14]. The composition of the swollen biopolymers has been studied with the method described in [15], using the microscope LOMO Mikmed-2 in the visible luminescence light, when illuminated from above with light exciting the luminescence. Pre-coloring of EPS preparations has been carried out with fluorochrome acridine orange [16]. The study on flocculation properties of microbial EPS preparations has been carried out within the process of wastewater chemical treatment, which includes dosing, mixing of extracted EPS with wastewater, flocculation, and deposition. Representative samples for laboratory study have been collected from the seafood- processing plant "Port Vladimir". Efficiency of wastewater treatment has been evaluated in ratio of total suspended solids, dissolved solids, and optical density in raw untreated and treated wastewater in accordance with standard methods 2 . The flocculating effect has been measured at 540 nm by determining the optical density of the treated water after flocculation for 100 minutes ( n ) with respect to the optical density of the raw untreated wastewater ( n 0 ) according to the following equation: 0 0 (%) . n n Flocculating effect n − = Results and discussion Extraction efficiency is an important technological parameter, which makes it possible to determine the feasibility of selecting and implementing the most effective technology for extracting EPS in the future. The amount of EPS obtained in this study is shown in Table 2. The maximum extraction efficiency is shown by the 1 A set of methods for hydrochemical control of activated sludge: determination of the mass concentration of activated sludge, sludge index, ash content of raw sludge, activated sludge, transparency of nadil water: federal register (FR): FR 1.31.2008.04397, FR 1.31.2008.04398, FR 1.31.2008.04399, 1.31.2008.04400. M. : AKVAROS, 2008. 37 p. (in Russian) 2 Quantitative chemical analysis of waters. The method for measuring the contents of suspended solids and total impurities in samples of natural and treated wastewater by the gravimetric method : HDPE F 14.1:2.110-97. М., 1997. 7 p. (in Russian) ; Quantitative chemical analysis of waters. The method for performing measurements of the mass concentration of dry residue in samples of natural and treated wastewater by the gravimetric method : HDPE F 14.1:2.114-97. М., 1997. 6 p. (in Russian)