Effect of the solids retention time on the rate of biodegradation of organic compounds

The paper studies the effect of the solids retention time (SRT) on the rate of biodegradation of morpholine (M), sulfanilic acid (SA), nitrilotriacetic acid (NTA), and ethylenediaminetetraacetic acid (EDTA) in laboratory mixed culture systems, fed semicontinuously on a once-a-day feeding schedule. It has been found that the minimum values of SRT at which microorganisms degrading the above compounds were washed out from the cultivation systems were 3, 1, 1, and 20 days for M, SA, NTA, and EDTA systems, respectively. A critical value of SRT was defined as that below which the rate of substrate removal is lower than the rate of substrate application into the system. The critical values of SRT were found to be 8, 3, 2.5, and above 20 days for M, SA, NTA, and EDTA systems, respectively. In a range between the minimum and critical values of SRT the mixed culture system cannot give stable efficiency of a given compound removal and the effluent concentration can be expected to vary considerably. Above the critical value of SRT, every cultivation system has a potential capability of shock loading treatment.     

Die frühmagmatische Bildung der Olivinausscheidungen vom Finkenberg (Siebengebirge) und Dreiser Weiher (Eifel)

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Kinetics of Oxidation of Lower Aliphatic Amines and Pyridine Derivatives by the Dichromate Method

The kinetics of oxidation of lower aliphatic amines and pyridine derivatives by dichromate was studied. It has been found that lower aliphatic amines and pyridine derivatives are oxidized by dichromate in acid medium. However, the oxidation rates are very low so that within the reaction period of 2 h, prescribed by the standard dichromate method, only a part of a given compound is oxidized. The kinetics of oxidation can be approximately described by an equation of the first order reaction. The lowest values of rate constants, of the order of 10^?3 h^?1, were found for pyridine and methylamines. The rate constants of ethylamines and pyridine derivatives are much higher, of the order of 10^?1 h^?1. Propylamine and butylamine are oxidized easily with high rates. The rate of oxidation of pyridine derivatives increases with an increasing number of substituents on the ring. Dimethylpyridines are oxidized faster than methylpyridines but slower than 2,4,6-threemethylpyridine. Oxidation of methyl derivatives of pyridine proceeds in two steps. In the first, relatively fast one, methyl groups are oxidized to carboxylic groups. In the second one, originated pyridinecarboxylic acids are slowly oxidized to carbon dioxide and water.     

Purification Limits of the Activated Sludge Process

Basic principles determining and substantiating the contents of organics in secondary effluents were formulated and discussed. It has been shown that the activated sludge process, if optimally designed and operated, can produce secondary effluents with soluble carbonaceous BOD₅ values below 5 mg/1 and suspended solids concentrations approaching 10 mg/1. While the total values of BOD₅ are significantly influenced by SS concentrations, the total values of COD are influenced mostly by soluble refractory organics present in raw wastewaters and formed in the process as microbial waste products.     

Bücher- und Zeitschriftenschau

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A study on lower fatty acids and polyethylene glycols adsorption on activated carbon

The dependence of the Freundlich constants on molecular weight of members of a homologous series was studied using lower fatty acids and polyethylene glycols. The adsorption was conducted on powdered activated carbon Carboraffin at 18±1°C. The obtained results may be summarized as follows: The adsorption of both fatty acids and polyethylene glycols may be satisfactorily described by the Freundlich adsorption isotherm. The constant K from the Freundlich equation increases with increasing molecular weight of both fatty acids and polyethylene glycols. The exponent n was found to be practically constant for fatty acids but to decrease with increasing molecular weight of polyethylene glycols. The pH of solution exerts an influence upon the adsorption of fatty acids and has no influence upon the adsorption of polyethylene glycols. The amenability of fatty acids to the adsorption decreases with increasing pH. No adsorption may be expected above pH of 8.2.     

Molmasseverteilung der organischen Stoffe im Prager Trinkwasser

The water supply of Prague is based upon three different water resources: artesian groundwater and infiltrate of the Jizera river, water of the Vltava and Zelivka rivers. The processing techniques are different; consequently for the purpose of increasing capacity one has to search for the suitable raw water quality as well as for the optimum treatment process. An essential parameter for this is the contents of organic substances whose molar mass distribution is investigated by gel chromatography with the aid of Sephadex G-10, G-25 and G-50. With respect to the total load of organic matter the Jizera shows the lowest values, in the Vltava the C.O.D. values are the highest, in the Zelivka the organic carbon shows the highest values. 80% of the organic substances in water have molar masses below 700. By flocculation 60… 70% of the C.O.D.-Cr can be eliminated, the optimum removal of the high-molecular substances occurring at pH = 6 and with 50… 60 g/m³ aluminium sulphate.