Sensitivity of coliphage T1 to nickel in fresh and salt waters

Accumulation and fraction distribution of Ni(II) in activated sludge treating Ni-laden wastewater

The accumulation and fraction distribution of Ni(II) in sludge was determined, and their effect on the performance of sequencing batch reactor (SBR) systems was evaluated at laboratory scale. The results showed that the removal efficiencies of substrates decreased significantly with increasing feeding concentration of Ni(II) into SBRs. The concentration of Ni(II) fed into the SBRs was significantly positively correlated with the Ni(II) contents accumulated in the sludge, while it was negatively correlated with the biomass in the SBRs. The accumulated Ni(II) in the sludge was distributed mainly in the available fraction, accounting for 75.8-90.0 % of the total Ni(II) content. The accumulated content of Ni(II) in each sludge fraction could be predicted satisfactorily by the feeding Ni(II) concentrations in the solutions. As compared with the total contents and other chemical fractions, Ni(II) in the oxidizable fraction in sludge exhibited more important inhibition effects on sludge microorganisms in the SBRs.

Long-term effects of Ni(II) on the performance and activity of activated sludge processes

The long-term effects of Ni(II) on substrate removal and microorganism activities were investigated by operating sequencing batch reactors (SBRs). Compared to the control system lacking Ni(II), the removal efficiencies of total organic carbon (TOC) and ammonium nitrogen (NH4(+)-N) in SBR system loading with 10mgL(-1) Ni(II) decreased drastically from 90.2±3.6 percent to 75.0±8.9 percent, and 99.2±0.6 percent to 50.8±11.5 percent, respectively. As compared to the control system, a inhibitory rate of more than 50 percent for the 2,3,5-triphenyltetrazolium chloride electron transport system (TTC-ETS) and the 2-(p-iodophenyl)-3-(p-nitrophenyl)-5-phenyltetrazolium chloride electron transport system (INT-ETS), and 43 percent for the specific oxygen uptake rate (sOUR) were detected in SBR system loading with 20mgL(-1) Ni(II). TTC-ETS, INT-ETS, and sOUR were significantly correlated with substrate removal efficiencies, suggesting that they could all serve as effective indicators of the performance of activated sludge processes. Additionally, INT-ETS is superior to sOUR and TTC-ETS in detecting the toxic effects of Ni(II) on sludge microorganism activity.

Investigation of the inhibitory effects of heavy metals on heterotrophic biomass activity and their mitigation through the use of natural minerals

This study examined the inhibitory effects of lead, copper, nickel and zinc on heterotrophic biomass and their potential mitigation through the use of low-cost, natural minerals. Activated sludge was placed in batch reactors and specific heavy metal concentrations were added. Subsequently, the biomass specific oxygen uptake rate (sOUR) was determined to assess the level of biomass inhibition. Biomass inhibition by heavy metals followed the order Cu(2+)>Pb(2+)>Zn(2+)>Ni(2+), with copper being the most toxic metal, causing high inhibition of heterotrophic biomass even at relatively low concentrations (i.e. 10 mg·L(-1)). Zn had very small toxic effect at 10 mg·L(-1), while at 40 mg·L(-1) the level of biomass inhibition reached 80%. Nickel stimulated activated sludge activity at concentrations of the order of 10 mg·L(-1). The addition of 10 g·L(-1) bentonite and zeolite in activated sludge resulted in the decrease of the inhibitory effect of heavy metals on biomass respiratory activity. In some cases, mineral addition was very favorable as inhibition was reduced from 69-90% to less than 55% and even up to 12%. The beneficial action of minerals is attributed both to the adsorption of heavy metals on the mineral and on the potential aggregation between mineral and sludge particles.

Single and combined effects of nickel (Ni(II)) and cobalt (Co(II)) ions on activated sludge and on other aerobic microorganisms: a review

Nickel (N(II)) and cobalt (Co(II)) are often encountered in wastewaters. As conventional wastewater treatment may only partially remove nickel and cobalt, a large fraction of the above metals is released to the aquatic environment. Both metals have been identified as micronutrients, at trace concentrations; however, they are both microbial growth inhibitors, at relatively high concentrations. On the other hand, the combined effects (e.g.: growth stimulation or toxicity) of the above metals have been found to differ from the summation of the effects which occur when the metals are applied individually. Moreover, a number of environmental factors (e.g.: pH, biomedium composition, biomass concentration, presence of other heavy metals) can affect the microbial toxicity of the above metallic species. The present review discusses, in a systematic way, the individual and joint effects of the above heavy metals to the growth of microorganisms grown under aerobic conditions, with focus on the growth of activated sludge. Data on multi-metal toxicity are particularly useful in establishing criteria for heavy metal tolerance levels in the environment.