Zbigniew Lewandowski

Inhibition coefficient (Ki) determination in activated sludge

Abstract A method of measurement of the inhibition coefficient, Ki, of chemicals within the activated sludge has been proposed. It makes possible the objective determination of the influence of non-competitive inhibitors on the reaction rate by means of simple respiration rate measurements with the application of a dissolved oxygen meter. The values of Ki for chromium Cr6+, for cyanide CN− and for two pesticides—DDVP and des-methyl DDVP was determined.

Inhibition of nitrification in the packed bed reactors by selected organic compounds

The effect of methanol, acetone, formalin and glucose on the nitrification process in the packed bed reactors has been investigated. For the utilized compounds the inhibition constant Ki was determined according to Dixons method. The determined values were as follows: methanol Ki = 116.0 mg l−1; acetone Ki = 804.2 mg l−1; formalin Ki = 61.5 mg l−1. The value of Ki for glucose has not been determined because glucose in applied concentration up to 11,325 mg l−1 had no effect on the nitrification course.

Behaviour of biological reactors in the presence of toxic compounds

Abstract A model of the influence of toxic compounds on the biological processes in waste water treatment reactors has been developed. The model predicts the behaviour of reactors influenced by toxic compounds acting as non-competitive inhibitors. The effects of a toxic compound on a process is quantified in terms of the inhibition coefficient Ki for the compound and the reactor resistance to inhibition values. The proposed model was utilized for the analysis of data obtained in a packed bed reactor for denitrification in the presence of chromium Cr6+. The inhibition coefficient for chromium was found to be 1.2 mg 1−1 Cr6+ and the reactor resistance to inhibition was 2.9 mg 1−1 Cr6+.

Denitrification by packed bed reactors in the presence of chromium (VI). Resistance to inhibition

Abstract The effect of chromium Cr 6+ on bacterial denitrification was investigated. The long-term influence of chromium presence was observed in packed bed reactors using methanol, ethanol, n -propanol, n -butanol, sec-butanol, tert-butanol, iso-butanol and n -pentanol as the carbon and energy sources for denitrifiers. Short-term influence was investigated by the inhibition coefficient K i determination within activated sludge under anoxic conditions. The measured inhibition constant K i was equal to 84.2 mg l −1 Cr 6+ , independently of the kind of organic compound utilized as the electron donor for the bacterial system. The concepts of the reactor resistance to inhibition (RRI) and the resistance to inhibition (RI) have been evaluated.

Biological denitrification in the presence of cyanide

Abstract The influence of cyanide presence on the denitrification process using methanol, propanol, sodium acetate, glucose and acetone as the energy and carbon sources were described. It was shown that during denitrification the carbonyl compounds used as the sole energy and carbon sources for denitrifiers can form cyanohydrins with the cyanide ion. The product of cyanohydrin hydrolysis is biodegradable serving as electron donors for denitrifying bacteria. The simultaneous denitrification and cyanide removal was proved.

Nitrification process in a packed bed reactor with a chemically active bed

Abstract A laboratory scale submerged filter filled with crushed marble was used for the nitrification process investigation. The results obtained showed that the alkaline reactor filling material react with the hydrogen ions released during the process course which enables reactor exploitation without any pH value or alkalinity control.

Biological reactor resistance to inhibition

Abstract The phenomenon of complete substrate conversion within biological reactors in the presence of toxic compounds, called the Reactor Resistance to Inhibition (RRI), has been investigated. It was theoretically demonstrated that the RRI value, which means the highest concentration of inhibitor by which complete substrate conversion is possible, depends on liquid detention time. The excess detention time over that required for complete conversion, imply the existence of a “reserve” reaction potential. The value of this “reserve” can be reduced by inhibitor action with no influence on the observed substrate conversion rate. The influence of detention time on biological denitrification in Packed Bed Reactors in the presence of chromium Cr 6+ was investigated. The RRI value for 1 h detention time was 1.5 mg l −1 Cr 6+ . For 3 h detention time the RRI value was 22 mg l −1 Cr 6+ . The relationship between the RRI value and detention time was linear.