Author: Dustov, Aziz Yusufovich

Annotation: Biofouling - the accumulation of microbial biofilms on the wetted surfaces of open recirculating (cooling-tower) water systems - is a critical technological and ecological problem of the oil-and-gas, chemical and power industries, because it simultaneously reduces heat-transfer efficiency, raises hydraulic resistance and, most seriously, drives microbiologically influenced corrosion (MIC). This paper analyses the biofouling regime of the recirculating cooling-water system of the Shortan Oil and Gas Production Department (Kashqadarya region, Uzbekistan) and evaluates complex biocidal-inhibitor strategies for its control. Under Shortan conditions the circulating water sustains sulphate-reducing bacteria (SRB), iron-oxidizing bacteria (IRB) and organic biofilm-forming microflora, with SRB counts of 102-104 CFU·mL-1 that rise sharply in summer at 32-38 °C; these organisms increase the corrosion rate by a factor of two to five locally and, through hydrogen-sulphide generation and FeS deposition, initiate dangerous pitting. Warm zones (30-40 °C), organic matter and low-flow regions favour biofilm formation, which accelerates MIC five- to fiftyfold and provides a substrate for further scaling. A copper-zinc complexonate approach to biocidal action was assessed as the most promising route: at optimal molar Zn:Cu ratios of 0.75:0.25 to 0.5:0.5 the copper-bearing complexonates suppressed up to 100 % of viable aerobic microorganisms relative to a control of 1800 CFU per unit volume, while retaining the ability to inhibit corrosion and calcium-sulphate crystallization. The compatibility of scale-and-corrosion inhibitors with oxidizing (hypochlorite, chlorine dioxide, hydrogen peroxide) and non-oxidizing (quaternary ammonium salts, isothiazolones) biocides is discussed, and a synergistic low-molecular-weight amine inhibitor plus biocide regime is proposed for Shortan. The combined program - biocidal dosing, oxygen and hydrogen-sulphide control, and continuous microbiological monitoring - is shown to restrain biofilm regeneration, reduce MIC and, together with corrosion-scale inhibition, extend equipment service life by 8-12 %.

Keywords: biofouling; microbiologically influenced corrosion; sulphate-reducing bacteria; biofilm; copper-zinc complexonate; biocide; recirculating cooling water; Shortan oil and gas enterprise.

Pages in journal: 16 - 26