Studies of the toxicological effect of aluminium compounds on the activated sludge biocenosis in aeration tanks

Summary

To provide for eliminating phosphorus from wastewater in the process of tertiary treatment in order to inhibit the eutrophication of the receiving water bodies iron- and alumunium containing chemical are used. At the wastewater treatment facilities operated by SUE «Vodokanal of St. Petersburg» chemical removal of phosphorus from wastewater was carried out with imported ferrous sulfate (III); beginning from 2012 domestically-produced aluminium sulfate has been used. Transfer to aluminium sulfate was supported with a series of experimental and research studies; one of them aiming at studying the toxic effect of aluminium and ferrous (III) salts on activated sludge in aeration tanks. The review of different assessments of the toxicity of aluminium compounds in relation to plants and animals in general is presented; the results of individual studies of the aluminium sulfate and ferrous (III) sulfate effect on the activated sludge biocenosis in aeration tanks are presented. During the analysis mixed liquor samples treated with different chemical dosages were fed with acetate ions and aerated for 18 hours under similar conditions; after that the sludge samples were subject to microscopic examination. The absence of any toxic effect of aluminium sulfate on the sludge biocenosis at the metal concentrations up to and including 64 mg/l was shown which exceeded the chemical dosages used in practice dozens of times. During the introduction of higher dosages of aluminium sulfate or ferrous sulfate the inhibition of aquatic life was caused by pH decrease; whereas at pH correction with alkali liquor no symptoms of the biocenosis inhibition was noticed. Further increase of chemical and alkali dosages up to 1000 mg/l as aluminium or iron caused the inhibition of aquatic life because of the total solids increase which is fatal for the fresh water biocenosis.

Key words

aeration tank , aluminium sulphate , aluminium , toxic effect , activated sludge resistance , resistance of indicator microorganisms of activated sludge

The experience of measuring aluminium ion in water

Summary

Practical use of the measuring techniques (specified in ПНД Ф 14.1:2:4.166-2000 and State Standard ГОСТ 18165-89) revealed a number of defaults in the process of determining low concentrations of aluminium in water. The technique of measurement is using the effect of aluminium-aluminon complex coloration with different chemical dosing methods. The experimental investigations showed that replacing successive addition of low concentrations of chemicals with reaction mixture improves the reproducibility of the results. However, the estimate accuracy of measurements (below 0.1 mg/l concentration) carried out with the certified aluminium determination techniques were not reached. Thus, the metrological performance of ПНД Ф 14.1:2:4.166-2000 and State Standard ГОСТ 18165-89 technique have to be revised the more especially that they have been widely used.

Key words

potable water , concentration , aluminium , aluminon solution , sample , absorbency

The use of DynaSand self-cleaning filters and Johnson Lamella Separators

Summary

The description of Nordic Water Products AB equipment for water purification and domestic and industrial wastewater treatment is presented. DynaSand self-cleaning filters and Johnson Lamella separators are reliable, efficient and simple in operation; they ensure sustainable high quality treatment of raw water. Contact filtration technology has been a great success in different countries, even when used in adverse climatic conditions with various types of water and wastewater.

Key words

potable water , wastewater , chromaticity , coagulation , iron , manganese , aluminium , self-cleaning filter , separator