Adsorption-oxidation technology of wastewater recycling in agroindustrial complex enterprises

Introduction. A large amount of wastewater is generated in processing of agricultural produce at agroindustrial enterprises. Almost all components of these effluents have an organic nature and can be efficiently processed under supercritical water oxidation to produce thermal and electrical energy. This requires a preliminary concentration of organic impurities, which can be carried out by adsorption method. This paper explores the possibility of adsorption wastewater treatment with nano-structured boehmite and wastes of agricultural enterprises with subsequent processing of the resulting sludge under supercritical water oxidation. Such a combination of adsorption purification of waste water from organic contaminants and their subsequent utilization in conditions of supercritical water oxidation has not been practiced before, and this is the novelty of the study. Unlike existing methods, this approach ensures efficient wastewater treatment with excess energy production. Materials and Methods. Nano-structured boehmites from different manufacturers and waste from agricultural enterprises (buckwheat hull, rice), coke production waste are used as adsorbents. The pore structure of the adsorbents was studied by low-temperature nitrogen adsorption. Microscopic examination was performed using an optical microscope. The content of organic substances was estimated by the index of chemical oxygen consumption. Crystallite size and phase composition were determined by x-ray method. Adsorption was studied on experimental samples of sour whey, sewage farms for growing cattle and pig farms, as well as waste of ethanol production. Results. Experimental studies demonstrated that buckwheat husks, rice and coke waste are nanostructured materials. A knife mill is the most effective for grinding waste. Isotherms of adsorption of organic impurities of waste waters on buckwheat husks and waste products of coke production are obtained. The quality of wastewater treatment increases with the raise in the specific surface area and the content of particles of the boehmite powder and the time of its mixing. Conclusions. The nanostructured powders have a sorption capacity in relation to dissolved organic substances and can be used for wastewater treatment of agricultural and processing enterprises and concentration of pollutants. Subsequent oxidation of saturated organic adsorbent in the conditions of supercritical water oxidation provides a full regeneration of the boehmite and the processing of organic matter to produce clean water and excess energy. This idea is promising to solve the problem of energy-efficient wastewater treatment agricultural enterprises.