Developing a unit for water pretreatment for the hybrid chemical-membrane purification system

Summary

At the present day developing and upgrading the methods for water pretreatment in membrane purification plants is a relevant objective. The purpose of this work has been the development and study of a small-sized water pretreatment unit based on the chemical method for the purification of heavily polluted water with high efficiency in terms of the degree of purification, chemical and energy consumption. A water pretreatment unit based on a dosing and mixing device for chemicals including jet hydrodynamic mixers – ejectors, has been developed. The device allows dosing chemical solutions in a wide range of injection coefficients and provides for improving the removal of hardness salts and heavy metals by more than 20%, and of oil products – by 8% compared to standard mixing with a blade mixer (120 rpm) owing to the mass transfer proceeding in an intense hydrodynamic field at Re >> Recr. Hybrid alumosilicic chemical was developed and studied that provided for reducing the concentration of toxic residual aluminum in purified water by an order of magnitude more (up to 0.02–0.05 mg/l) in comparison with other aluminum-containing reagents owing to the formation of mesoporous alumosilicic structures possessing the effect of volumetric sorption in 6–8 pH range. An experimental model of a portable water treatment plant with a unit of chemical pretreatment and membrane post-treatment based on the microfiltration technology using a porous titanium carbide membrane and low-pressure reverse osmosis technology with the use of a membrane made of a thin-film polyamide composite has been designed. It is shown that using a pretreatment unit provides for increasing the performance of the microfiltration device up to 3.7 times while removing oil products and hardness salts from water, and up to 4.3 times while removing heavy metals (copper). It is also shown that the developed version of the portable plant provides for a preset degree removing the main pollutants from heavily polluted wastewater in at the lowest specific energy consumption of 2.57 kWh/m³ compared to the analogues.

Key words

mobile plant , reagent treatment , microfiltration , water treatment , hybrid system , pretreatment , membrane methods , low-pressure reverse osmosis