Hidrológiai Közlöny 1971 (51. évfolyam)

1. szám - Varró István: Felszíni vizek tisztításának korszerű módszerei és anyagai

Special Conference Number, Szebellédy, L. Hidrológiai Közlöny 1971. 1. sz. 43 1. The flow which must always be maintained in the canal is at least 5 cu.m/sec, except for drainage- and flood periods. 2. Polluted water of the Tisza River must not be admitted to the canal during the passage of the pollution wave. 3. Wastes, even after treatment, must not be discharged into the canal. 4. After drainage is completed, the canal must be flushed with water from the clean Tisza River. 5. An auxiliary reservoir must be created whence water is drawn while the canal carries polluted water. For this reason treatment technology must always be adjusted to the quality of raw water delivered in the canal. The addition of aluminiumand iron salts, aetivated silica and lime, activated carbon, potassium permanganate, ozone, chlorine and ammónia has been envisaged for treatment. In generál 4 to 5 different chemicals are fed simultaneously. Vertical-flow, sludge curtain clarifiers, equipped with mechanical flocculators are construced. This at the same time serves the purposes of sludge recirculation. Water is fed to the distribution network after chemical-feed rapid filtration, treatment with chlorine and ozone. It is emphasised that preliminary research and experiments play an important role in designing treatment plants. One would be inclined to conclude that no design must be attempted without carefully planned preliminary studies and technological tests at small pilot plants. The economics of treating surface water are considered in the paper by I. Varró, entitled "The treat ment of surface water by intermittant chemical feed". A treatment technology has been developed at the Enterprise for Soil Exploration and Surveying, and appüed subsequently in practice, where the feed of chemicals is not continuous, but occurs only for 2 hours after operation is started, or from the beginning of the filtering period. The gelatinous film developed in the filter sand during the feeding period, thereafter the colloidal and other substances accumulated within this film are called upon to remove the organic and inorganic suspended substances present in surface water. After the discontinuation of chemical feed filtering is continued until permitted by the filter resistance. The filter must then be flushed using water and air, if possible. The advantages of the process are as follows: 1. The pH of water need not be adjusted and thus no secondary treatment is necessary. 2. The saving in chemicals is appreciable. 3. The load on the filter is about 15 kg/sq. m. 4. The filter period is from 10 to 12 days. 5. The consumers are supplied with water of the originál fundamental composition, with is not aggressive. 6. In the flushing operation treated water and energy can be saved. The process can be used for treating raw water containing up to 50 mg/lit suspended matter. In other cases a micro-drum filter must be applied before rapid filtration. A cost-benefit analysis of the method has been omitted, this being included in detail in the paper of Hembach—Bayer. The paper submitted by I. Varró and K. Hembach deals with the treatment of watter obtained from a small reservoir in the vicinity of Pécs, where water could not be obtained unless byutilizing a small watercourse. The problem was solved by ereating a small reservoir of a size permitted by the particular circumstances, which serves at the same time as a preliminary settling basin. The technology of treatment consisted in the intermittent chemical feed process just deseribed, involving conditioned filters. The resulting technology proved simple and economic. Data processed so far indicate that under conditions prevailing in Hungary, up to capacities of round 10,000 cu.m/day plants with closed, pressurized filters appear to be economically superior. The economics of the intermittent chemical feed; technology in the treatment of surface water is analysed in detail by K. Hembach and A. Bayer. Their paperis entitled "Problems of economics and site selection in planning waterworks supplied by surface water". For obtaining the most economical solution detailed investigations have been carried out inta the relationships controlling the economics of storage, plánt siting, conventional and intermittent feed technologies. It should be noted in advance that in dry weather the necessary rate of flow cannot be diverted from the watercourse. Owing to the scarcity of water and to local conditions. the creation of a large reservoir proved not feasible. The water deficiency must be supplied on occasion from the municipal waterworks. For this reason, in determining the minimum storagerequirement allowance has been made for the runoff from rainfall, but alsó the volumeof water purchased from the municipal waterworks in dry weather and the possibility of returning it in rainy periods, From these estimates it was concluded that the economical size of the reservoir is essentially controlled by the long-term equality of purchased and return water. Alsó, estimates have shown the investment cost of treatment by the new conditioned-filter technology to be lower by about 25 to 50 percent — depending on the quality and suspended content of raw water—than that for conventional methods of treatment. The saving in operating costs has been estimated at about 35 to 50 percent. Technological problems related to the treatment of surface water are dealt with alsó in the paper by G. Werner. A treatment plánt of 4000 lit/sec capacity is under construction at Ulm in Western Germany, where water from the Danube will be treated to drinking quality. The pilot plánt had a capacity of 20 lit/sec, where experiments were conducted over 4 years. Owing to the heavy pollution of the river a more sophisticated method of treatment became necessary. Filtration must be preceded by careful pretreatment, which is possible in contact floating sludge reactors only. The chemi-