Acute and Chronic Toxicity of Acid Mine Drainage to the Activated Sludge Process

Abstract

The combined treatment of acid mine drainage (AMD) and municipal wastewater using the activated sludge process is an innovative approach to AMD remediation. The toxicity of synthetic AMD to activated sludge was evaluated using oxygen uptake rate (OUR) inhibition tests, which showed that activated sludge can withstand high proportions of AMD (EC 50 19-52% AMD by volume). The EC 50 values of municipal and industrial activated sludges were significantly different (p \ 0.05), with municipal sludges exhibiting higher tolerance to AMD. Although the EC 50 values for heterotrophic and nitrifying activated sludges were not statistically significantly different, the EC 50 values for heterotrophic bacteria were generally higher. Laboratory-based sequencing batch reactors were used to examine the treatability of AMD. Increased concentrations of COD and suspended solids, associated with turbidity and poor floc morphology, were observed in the final effluent after extended AMD loading. Protozoan community structure changed during the AMD loading period, and overall abundance tended to decrease over time. OUR decreased in the AMD-loaded reactors, particularly in the reactor receiving the highest AMD load, indicating reduced biomass activity over the acclimatization period. Results from OUR inhibition tests on the acclimatized activated sludge indicated that over a relatively short timescale (21 days), the activated sludge microbial community can adapt to AMD sufficiently so that shock loads of metals and acidity do not significantly inhibit OUR. These preliminary studies indicate that it is possible to treat AMD successfully in admixture with municipal wastewater using the activated sludge process.

Effect of arsanilic acid on anaerobic methanogenic process: Kinetics, inhibition and biotransformation analysis

“…After 5 days incubation, the methane production began to recovered, indicating that anaerobic methanogenic bacteria had adapted to arsanilic acid concentration. The elimination of inhibition after a certain exposure time could be attributed to factors such as acclimatization to contaminant of microorganisms, transition of dominant methanogenic species [23,24], adsorption of toxic compounds on flocs of sludge, and/or biological transformation of a toxic compound to a less toxic species [25] during exposure. As shown in Fig.…”

Impacts of Gadolinium and Yttrium on the Performance and Microbial Community Composition of a Bench-Scale-Activated Sludge System

“…Test reactors were exposed to synthetic wastewater spiked with gadolinium (Gd) or yttrium (Y). Synthetic wastewater enabled a constant composition feed and allows for interpretation of wastewater treatment performance data independent of influent variability. − Gd was selected based on its documented presence in WRRFs and their receiving waters (recognizing that the majority of Gd occurs as a soluble chelate), − and Y was chosen to build on prior research, indicating impacts from this element to model nitrifying organisms. , The total Gd and Y treatment concentrations in test reactors ranged between 1 and 50 mg/L. These concentrations were selected to align with REE loading concentrations between tens and hundreds of mg/L that have been identified in REE extraction and leaching processing water − and to further explore the findings of Fujita et al (2015), who identified inhibition to nitrifying pure cultures when exposed to Y at concentrations exceeding 10 mg/L.…”