Domestic wastewater treatment by reverse osmosis

Summary

Possible treatment of domestic wastewater by the reverse osmosis with the purpose of producing high-quality effluent suitable for the discharge into fishery water bodies or for the use as process water has been investigated. Possible recycling of reject water from a reverse osmosis unit by drastically reducing the flow rate to the value less than 0.5–1% of the incoming flow and removing the reject water as a moisture component of the dewatered sludge is presented. Experiments have been carried out to determine the change in the concentration of dissolved solids in the filtrate of the membrane apparatus and a decrease in the membrane capacity in the process of wastewater treatment and reject water flow reduction. The obtained dependencies allow to determine the following: the required flow rate of the reject water depending on the concentration of suspended solids and COD; the required filtrate yield depending on the concentration of ammonium in raw wastewater. The methodology for determining the surface area of membranes and the number of membrane apparatus at each stage of wastewater treatment is described. The optimal values of working pressure, economic indicators of the unit in comparison with other wastewater treatment technologies were determined.

Key words

reverse osmosis , concentrate utilization , domestic wastewater , reduction of reject water flow , apparatus with an open channel , membrane selectivity

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Wastewater treatment of a cottage estate. Design and operational errors

Summary

The principle of operation, as well as the errors while designing and operating a compact wastewater treatment plant with a design capacity of 500 m³/day (actual flow rate is 250–280 m³/day) are considered. The treatment facilities have been designed in two phases and include the stages of mechanical and biological treatment, followed by tertiary treatment in biofilters with expanded clay media, and UV disinfection of the effluent after biological treatment. Gravity sludge thickeners and dehydrators are provided for processing the resulting sludge. Upon the detailed consideration of the design solutions, as well as the problems revealed during the operation, design errors were identified that made it impossible to ensure the required quality of wastewater treatment. Currently, to enhance the operation of the complex, a number of facilities are being upgraded. This will provide for reaching the stable operation of the complex and ensuring the standard indicators at the MPC level for organic and suspended solids in the effluent before being discharged into a water body.

Key words

wastewater treatment , bioblock , domestic wastewater , compact plant , cottage estate , проблемы эксплуатации