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

Скачать/download (PDF) free access

Solid waste landfill leachate treatment and utilization of reverse osmosis reject water

Summary

The leachate of solid water municipal landfills contains high concentrations of organic waste decomposition products and mineral salts. COD concentrations in organic substances can reach 5,000 mg/l; of ammonium ions – 2,500 mg/l; of total dissolved salts – 15,000 mg/l. In order to meet the current regulations on the discharges into the environment including fishery water bodies, the treatment of such wastes by two- or three-stage reverse osmosis is required. The performance of modern reverse osmosis membranes designed for demineralization of groundwater and sea water is low due to high salinity and COD levels in wastewater. Experimentally, the main dependences of the required reject water flow on the degree of ammonium ion removal were obtained. The use of nanofiltration membranes provides for reducing the reject water flow and operating costs. For the utilization of the reverse osmosis reject water, separating the waste flow into the following streams is proposed: with a high concentration of organic substances and with a high concentration of mineral salts, such as sodium and ammonium chlorides.

Key words

reverse osmosis , membrane selectivity , municipal solid waste landfill leachate , permeate yield increase , membrane performance decrease , membrane replacement expenditures