DOI 10.35776/MNP.2020.05.06
UDC 628.32:66.081.63

Pervov Aleksei, Tikhonov Konstantin

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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DOI 10.35776/VST.2022.08.07
UDC 628.32:66.081.63

Shirkova T. N.

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

UDC 628.32.66.081.63
DOI 10.35776/VST.2025.03.06

Shirkova T. N.

Reducing the flow of reverse osmosis concentrate in the process of solid waste landfill leachate treatment

Summary

Leachate of the municipal solid waste landfills is a major environmental hazard. Reverse osmosis technology is used for leachate treatment. The disadvantage of using reverse osmosis is generation of a large amount of concentrate because its disposal involves high costs. A technology is presented that provides for reducing concentrate flow to values ​​that ensure the economic feasibility of its evaporation or removal by trucks. Reducing concentrate flow is achieved by changing the ratio of salt ion concentrations and organic substances. The separation of the concentrate solution is effected owing to the difference in the retention capacity of low-pressure nanofiltration membranes in relation to organic substances and monovalent salt ions. The separation of the concentrate solution provides for reducing not only its flow, but also the costs of its disposal, that is to process and reduce the volume of each solution separately at lower costs. A method for conducting experiments is presented, the results of the separation of the concentrate solution are given, as well as technical and economic calculations that allow comparing the effectiveness of the proposed approach with the traditional solution based on the use of high-pressure membranes.

Key words

filtrate , concentrate , reverse osmosis , reverse osmosis unit , nanofiltration , membrane selectivity , low-selectivity membranes , solid municipal waste landfill