Toxic influence of silver and uranium salts on activated sludge of wastewater treatment plants and synthetic activated sludge associates modeled on its pure cultures

Abstract

Toxic impact of silver and uranium salts on activated sludge of wastewater treatment facilities has been studied. Some dominating cultures (an active nitrogen fixer Agrobacterium tumifaciens (A.t) and micromyces such as Fusarium nivale, Fusarium oxysporum, and Penicillium glabrum) have been isolated and identified as a result of selection of the activated sludge microorganisms being steadiest under stressful conditions. For these cultures, the lethal doses of silver amounted 1, 600, 50, and 300 µg/l and the lethal doses of uranium were 120, 1,500, 1,000, and 1,000 mg/l, respectively. A.tumifaciens is shown to be more sensitive to heavy metals than micromyces. Synthetic granular activated sludge was formed on the basis of three cultures of the isolated micromyces steadiest against stress. Its granules were much more resistant to silver than the whole native activated sludge was. The concentration of silver causing 50 % inhibition of synthetic granular activated sludge growth reached 160-170 μg/l as far as for the native activated sludge it came only to 100-110 μg/l.

A Study of Toxic Dosage of Combined Selenium and Hexavalent Chromium on Activated Sludge Bacteria

“…Some of them mentioned that activated sludge growth is inhibited at Cr 6+ concentrations above 5 mg/L, while others report growth inhibition at concentrations above 25 mg/L. However, all researchers agree that Cr 6+ is definitely an activated sludge growth inhibitor at higher concentrations [4,19,24,35].…”

“…A few studies addressed the toxic influence of heavy metals on activated sludge of municipal wastewater treatment plants [4,19,[23][24][25]. Tyupa DV, et al [19] reported lethal doses of silver at 1, 50, 300, and 600 µg/L and lethal doses of uranium at 120, 1,500, and 1,000 mg/L, respectively, in activated sludge from a wastewater treatment plant. Liu G and Wang J [24] investigated the effect of nano-copper and nanomagnesium particles on activated sludge.…”

“…Furthermore, high selenate concentrations from the stormwater runoff are readily bioavailable for microorganisms in sewage systems. Moreover, wastewater treatment systems often receive more than one metal simultaneously [19]. Hexavalent chromium is one of the toxic heavy metals which come from various industrial activities such as plating facilities, power plants, mining, electrical equipment manufacturing, leather and wood industry, surface…”