Vízügyi Közlemények, 1969 (51. évfolyam)
4. füzet - Rövidebb közlemények és beszámolók
(74) DETERMINATION OF DESIGN CRITERIA FOR ACTIVATED SLUDGE TREATMENT PLANTS, BY MODEL TESTS By Dr. P. Farkas and Á. Németh (For the Hungarian text see 395) The design criteria for wastes treatment plants operating by the activated sludge process are determined by site surveys and model tests. The most important criteria are: the rate of raw wastes inflow, the concentration of wastes measured in BOI) 5 and COD, the fluctuations of these values, the desired quality of the effluent, the volume of the aeration basin, the daily rate of oxygen introduction, and the volume of sludge produced. The data gained in the course of the site survey are completed by laboratory tests, respirometry and activity measurements, by which the biological decomposability, occasional toxicity of the wastewater are determined and informative data are obtained on the residence time to be realized in the prototype. The information gained in the laboratory tests, model tests with continuously operated models of 3 to •50 lit. volume are performed. In Lhe automatically fed models the rate of wastewater inflow is adjusted to obtain different sludge-load values, which include the range corresponding to the anticipated method of operation in the prototype. From the daily analytical and respirometric data of raw waste and effluent, as well as of sludge, the specific decomposition rate ol organic matter, further the specific rates of oxygen consumption and sludge production are determined. From these the constants of the mass balance equations are computed, which are used for estimating —from the material data of raw wastes —the daily oxygen demand and excess sludge production of the plant to be designed. The decomposition rate constant of organic matter is used for estimating the time of residence and therefrom the aeration volume required. By observing the particular considerations of dimension enlargement, the results of model tests may, in general, be transferred directly to the prototype. On the basis of model results the probable investment and operation costs of the prototype may also be estimated. ANALYSIS OF SETTLING TANKS AND THE DETERMINATION OF SOME OF THE MAJOR DESIGN CRITERIA By I. Horváth and L. Muszkalay (P'or the Hungarian text sec pp. 413) An analysis of hydraulic processes in settling tanks is presented, with special regard to settling tanks of the Dorr-system. The main design parameters (time of residence, surface loading, in- and outflow arrangements, etc.) are considered with the aim of determining the optimum design of structures. It is concluded that in establishing the optimum value of the hydraulic loading and, in turn, of the outflow T edge loading, hydraulic and settling conditions must be taken simultaneously into consideration. In connection with different in- and outflow solutions it is demonstrated that flow- and settling conditions alike may be affected appreciably by deficiencies of construction work, which may result in the formation of large areas of stagnation in the settling tank. From this respect it is of paramount importance to construct the inlet- and outflow elements accurately true to plan. Hydraulic efficiencies representative of flow conditions in the settling tank are then analysed in the light of reactor technology, concluding that hydraulic efficiencies can be given a clearer physical interpretation in terms of the perfect tube reactor and perfect tank reactor. Experiments have been conducted with the soealled flow-through technique. In this context the advantages accruing from the determination of the flow-through curve, in observation and processing are emphasized, pointing at the same time to
