Influence of Water Acidation Degree on Quality of Permeate of a Reverse Osmosis Plant

Summary

The results of industrial tests of the plant of reverse osmosis water desalination installed in the chemical water treatment shop of the Samara hydropower station are presented. Influent water is subjected to pre-treatment in clarifiers with liming, filtering on mechanical filters and two-stage Na-cation exchange. The influence of acid doses in the course of influent water acidification and the value of permeate output on its quality is studied. The evaluation of convergence of calculated data performed with the help of specialized software with the actually received values of permeate quality is made. Оbserved dependences allow us to make adjustments of the permeate quality obtained by the calculation method.

Key words

reverse osmosis , selectivity , desalination , membrane technology

DOI 10.35776/VST.2021.03.05
UDC 628.355:62-278

Lominoga O. A., Kuz’min Valentin, Koloskova Evgeniia

Introduction of membrane technologies at the wastewater treatment facilities of Molodezhnoe settlement

Summary

The experience of introducing membrane wastewater treatment technology at the wastewater treatment facilities in Molodezhnoe settlement (St. Petersburg) is presented. The treatment facilities include: a main pumping station, a combined mechanical wastewater treatment plant, a wastewater regulator, a bioreactor (aeration tank operating using nitri-denitrification technology) for enhanced nitrogen removal, a membrane bioreactor, an ultraviolet effluent disinfection unit, a screw press for excess activated sludge dewatering, aluminum sulfate dosing unit for the chemical removal of phosphorus compounds (phosphates). The effluent after disinfection is discharged through a deep-water outlet into the Gulf of Finland. Membrane filtration provides for the enhanced tertiary treatment to remove fine suspended solids and colloidal particles. To achieve a stable quality of the effluent during the operation of membrane modules, the following requirements shall be strictly met: the high efficiency of screenings removal; prevention of the ingress of foreign particles into the bioreactor after mechanical treatment; high concentration of sludge in the aeration tank and membrane unit; timely chemical washing of the membranes. During the trial operation of the treatment facilities in Molodezhnoe, the irregular hydraulic and pollution loading was noted. During the operation period the operating modes of the facilities were adjusted with account of the irregular characteristics of the incoming flow while achieving the design parameters of the process line of wastewater treatment.

Key words

wastewater , advanced biological treatment , transmembrane pressure , membrane module , membrane technology , hydraulic loading

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UDC 628.16.066.7

Volftrub L. I.

Upgrade of clarifiers at energy facilities with the use laminar modules

Summary

The need for upgrading clarifiers of obsolete and outmoded design is substantiated. The clarified water quality and capacity of these facilities do not meet the modern water treatment requirements which can be explained by the design and technological characteristics of these facilities. The suggested technical solutions aim at the elimination of such deficiencies as unstable turbulent mode of the suspension settling in a sufficiently high layer (1.5–2 m), low volume utilization factor of clarifiers, the lack of an efficiently operating flocculation chamber. The experience of introducing laminar modules in the water treatment sections of energy facilities is quoted. The upgrade of pretreatment facilities, production of clarified water with low suspended solids, iron and organics concentrations will provide for improving the technical and economic performance of the water treatment units and introducing advanced technologies at the subsequent water treatment stages.

Key words

natural water , membrane technology , clarifier , honeycomb module , pretreatment , laminar module

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UDC 628.165:62-278:621.311.21

Tsabilev O. V., Strelkov A. K.

Evaluation of full-scale reverse osmosis unit operational parameters

Summary

Undissolved and dissolved substances present in the water supplied to a reverse osmosis unit can form deposits. To minimize their negative effect the equipment for water pretreatment that ensures the water quality meeting the requirements set by the membrane elements manufacturers has been retrofitted into the general process flow scheme. The basic operational parameters of a full-scale reverse osmosis unit with spiral wound reverse osmosis elements are presented. Mathematical processing of the operational parameter values was carried out, the results gained were plotted. The changes in the operational parameters before and after chemical washing of the membrane elements are shown. The evaluation of the convergence of the design and actual data under the conditions considered is given. The quoted relationships allow evaluating the operational parameters of the membrane elements, determining the washing interval and efficiency of the chemical washing. The use of the presented method of evaluating the operational characteristics will also allow substantiating the warranty claims to the manufacturers of reverse osmosis units and membrane elements.

Key words

reverse osmosis , desalination , membrane technology , permeate , chemical washing , membrane element

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UDC 628.161.2:614.777:546.47/.49

Larionov S. Iu., Panteleev Aleksei, Riabchikov Boris, Shilov Mikhail, Kasatochkin A. S.

Removal of natural radionuclides from underground water sources

Summary

Natural radionuclides are present in underground water sources of some Russian regions in the concentrations exceeding the maximum permissible level for drinking water. Natural water radioactivity is caused by the presence of uranium 238U and thorium 232Th isotope decay products including radium and radon. For the purification of radium containing water lime softening, sorption on special adsorbents (e. g. zeolites), ion exchange softening and active aluminium oxide or active alumina, manganese containing media are used. The given methods of treatment are described in a number of publications that state the possible use of reverse osmosis or nanofiltration, however, lack the information on their application. Membrane technologies in combination with the traditional methods allow designing the flow scheme of radionuclides removal from underground water. During the tests on producing water of the required quality for an open-cycle heat supply system no radionuclides accumulation was observed. For the operation period (1.5 month) of the ultrafiltration plant during the interval between backwash cycles the radiation background straight at the membrane increased insignificantly; whereas, after the backwash it returned to the initial level. Backwash number was more than 100 providing for the statistically valid data. The reverse osmosis plant was operating with ultrafiltration permeate. The total radionuclides in the parent solution was about 1.4 Bq/l, in reverse osmosis filtrate – 0.005 Bq/l, i. e. much lower than the maximum permissible level. In reverse osmosis concentrate this value does not exceed 1 Bq; therefore, it can be discharged into the open hydraulic networks in compliance with the established standards. No activity accumulation on the reverse osmosis membranes was observed.

Key words

aeration , reverse osmosis , ultrafiltration , nanofiltration , membrane technology , water treatment , radionuclides , radioactive wastes

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UDC 628.112

Larionov S. Iu., Panteleev Aleksei, Riabchikov Boris, Shilov Mikhail, Kasatochkin A. S.

Cleaning up underground water from chlororganic compounds

Summary

Chlororganic compounds present in underground water are technogenic pollution products. The water in a number of deep wells that supply Podolsk and Troitsk cities in the Moscow Area with water is characterized by elevated concentrations of volatile chlororganic compounds (carbon tetrachloride, trichloroethylene and tetrachlorethylene). To provide for water purification according to the drinking water standards a number of technologies is suggested: surface aeration, ozonation, activated carbon treatment, sorption on activated carbon, membrane filtration. The technology of removing volatile chlororganic compounds from water was tested in an experimental plant including primary aeration of raw water in a vacuum-ejection unit with subsequent filtration in filters with granulated activated carbon, and salt composition correction with nanofiltration. The operation of a unit with primary ozonation of water before supply to the carbon filter was tested. It was shown that aeration provided for 50–80% removal of volatile chlororganic compounds which could significantly improve the operating life of a carbon filter. After treatment with activated carbon the concentration of all chlororganic compounds was lower compared to the regulations. Since water ozonation involves high ozone consumption ozone dosage higher than 100 mg/l is required to ensure the reduction of trichloroethylene and tetrachlorethylene concentrations to the standard value. Tetrachlorethylene is oxidized heavier than other compounds (the regulatory concentration is not reached). Nanofiltration with «Nano NF 4040» membrane manufactured by «RM Nanotech» domestic producer provides for water purification according to Sanitary Regulations and Norms 2.1.4.1074-01 without using any other technologies. However, nanofiltration involves primary water treatment – de-ironing and mechanical filtration.

Key words

potable water , aeration , membrane technology , pilot tests , volatile chlororganic compounds , nanofiltration

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