Effects of long-term addition of Cu(II) and Ni(II) on the biochemical properties of aerobic granules in sequencing batch reactors

Abstract

Copper (Cu(II)) and nickel (Ni(II)) are often encountered in wastewaters. This study investigated the individual toxic effects of long-term addition of Cu(II) and Ni(II) on the biochemical properties of aerobic granules in sequencing batch reactors (SBRs). The biochemical properties of aerobic granules were characterized by extracellular polymeric substances (EPS) content, dehydrogenase activity, microbial community biodiversity, and SBR performance. One SBR was used as a control system, while another two received respective concentration of Cu(II) and Ni(II) equal to 5 mg/L initially and increased to 15 mg/L on day 27. Results showed that the addition of Cu(II) drastically reduced the biomass concentration, bioactivity, and biodiversity of aerobic granules, and certainly deteriorated the treatment performance. The toxic effect of Ni(II) on the biodiversity of aerobic granules was milder and the aerobic granular system elevated the level of Ni(II) toxicity tolerance. Even at a concentration of 15 mg/L, Ni(II) still stimulated the biomass yield and bioactivity of aerobic granules to some extent. The elevated tolerance seemed to be owed to the concentration gradient developed within granules, increased biomass concentration, and promoted EPS production in aerobic granular systems.

Changes in functional diversity of soil microbial community with addition of antibiotics sulfamethoxazole and chlortetracycline

“…EcoPlate, one kind of Biolog Microplate, has been successfully applied to study the effect of sulfachloropyridazine on the pollution-induced community tolerance (PICT) of soil microbial communities (Schmitt et al 2004). There are still some criticized opinions about the utilization of the Biolog method because the Biolog Microplate mainly reflects a part of microbial community in environmental samples, but it has proved to be a useful tool to differentiate disturbance in soil microbial functional diversity and community from different environmental stresses (Du Plessis et al 2005;Hayyis-Hellal et al 2009;Liu et al 2009b;Lupwayi et al 2009;Wang et al 2010).…”

Interaction between Heavy Metals and Aerobic Granules

“…This EPS matrix protected microorganisms from exposure to high concentrations of metals. Moreover, research also found that microorganisms could regulate EPS synthesis and modify EPS components (Sheng et al, 2005;Wang et al, 2010). They would secrete more EPS in the presence of heavy metals, especially more proteins.…”

“…However, results from these studies are difficult to be compared due to the various metal bioavailability caused by different operation modes, substrate compositions, seed sludge sources and concentrations. The total organic carbon (TOC) removal efficiency of activated sludge process decreased from 98% to 88% in the presence of Ni (II) while the same Ni (II) loading rate exerted slight influence on aerobic granules system (Ong et al, 2004;Wang et al, 2010). Table 4 gives the metal/VSS ratios causing 50% inhibition of microbial activity of anaerobic granules and flocculent sludge.…”

“…However, the oxygen consumption zone was stretched, implying the migration of aerobe into inner space to avoid metal toxicity or/and the metabolism switch of facultative aerobic microorganisms to aerobic respiration which is more efficient than the original fermentation. Wang et al (2010) applied Biolog tests to analyze the substrate utilization patterns of aerobic granules before and after long-term metal addition. Principal component analysis of the Biolog tests and the hierarchical cluster analysis showed different groups based on metal treatment, indicating changes in microbial community structure induced by Cu and Ni (Fig.…”

Chemicals and Allied Products Waste Treatment

“…Wang et al experimented using aerobic granules in three sequencing batch reactors (SBR, One SBR was a control, while two had Cu(II) and Ni(II) with the heavy metal concentrations increasing to 15 mg/L. The results determined that Cu(II) was affected by biomass concentration, bioactivity, and biodiversity of the aerobic granules [46].…”