Microbial community shifts in the oxic-settling-anoxic process in response to changes to sludge interchange ratio

This particular study set out to demonstrate alterations on the microbial community of the oxic-settling-anaerobic/anoxic (OSA) process treating real domestic wastewater by changing interchange ratios (IRs). The sludge yield of systems operated at different IRs (1/13, 1/17 and 1/20) to assess sludge reduction was used to analyze microbial community composition variations. The highest IR (1/13) resulted in the highest sludge reduction (52.1%), while the OSA systems with IR of 1/17 and 1/20 reduced sludge production by 37.4% and 35.5%, respectively, in comparison to conventional systems. 16S rRNA gene amplicon sequencing analysis showed that the bacterial communities were composed of similar phylogenetic groups, Proteobacteria, Acidobacteria, and Bacteroidetes being dominant. The relative abundances differed due to the applied IRs. The highest abundance of Actinobacteria was determined at the highest IR (1/13) and increasing of the HRT to 1/20 caused a significant reduction in Actinobacteria species and the lowest abundance (6%) was determined in the OSA systems. The abundant of Thiothrix species that are boosted in the OSA trials may have a vital role in OSA systems, where its abundance was below the detection limits in the seed sludge sample. Therefore, they could be used as bioindicators in the OSA system

Combined sewer overflows: A critical review on best practice and innovative solutions to mitigate impacts on environment and human health

Combined sewer overflows (CSOs) are of major environmental concern for impacted surface waterbodies. In the last decades, major storm events have become increasingly regular in some areas, and meteorological scenarios predict a further rise in their frequency. Consequently, control and treatment of CSOs with respect to best practice examples, innovative treatment solutions, and management of sewer systems are an inevitable necessity. As a result, the number of publications concerning quality, quantity, and type of treatments has recently increased. This review therefore aims to provide a critical overview on the effects, control, and treatment of CSOs in terms of impact on the environment and public health, strict measures addressed by regulations, and the various treatment alternatives including natural and compact treatments. Drawing together the previous studies, an innovative treatment and control guideline are also proposed for the better management practices

Bioenergy production from diluted poultry manure and microbial consortium inside Anaerobic Sludge Bed Reactor at sub-mesophilic conditions

In this study, anaerobic treatability of diluted chicken manure (with an influent feed ratio of 1 kg of fresh chicken manure to 6 L of tap water) was investigated in a lab-scale anaerobic sludge bed (ASB) reactor inoculated with granular seed sludge. The ASB reactor was operated at ambient temperature (17-25 degrees C) in order to avoid the need of external heating up to higher operating temperatures (e. g., up to 35 degrees C for mesophilic digestion). Since heat requirement for raising the temperature of incoming feed for digestion is eliminated, energy recovery from anaerobic treatment of chicken manure could be realized with less operating costs. Average biogas production rates were calculated ca. 210 and 242 L per kg of organic matter removed from the ASB reactor at average hydraulic retention times (HRTs) of 13 and 8.6 days, respectively. Moreover, average chemical oxygen demand (COD) removal of ca. 89% was observed with suspended solids removal more than 97% from the effluent of the ASB reactor. Influent ammonia, on the other hand, did not indicate any free ammonia inhibition due to dilution of the raw manure while pH and alkalinity results showed stability during the study. Microbial quantification results indicated that as the number of bacterial community decreased, the amount of Archaea increased through the effective digestion volume of the ASB reactor. Moreover, the number of methanogens displayed an uptrend like archaeal community and a strong correlation (-0.645) was found between methanogenic community and volatile fatty acid (VFA) concentration especially acetate

Acute effects of various antibiotic combinations on acetoclastic methanogenic activity

Pharmaceutical production industries are one of the main sources of antibiotics, and they release considerable amounts of antibiotics to ecosystem. Antibiotics usually present as mixtures in treatment plants and have negative effect on biological processes. In this study, batch acute tests were performed to assess the inhibitory impacts of selected antibiotic combinations of sulfamethoxazole and tetracycline (ST), erythromycin and sulfamethoxazole (ES), and erythromycin and tetracycline (ET) on acetoclastic methanogenic activity. Each antibiotic was equally applied, making the total concentrations in the mixtures 0 (control), 2, 20, 50, 100, 250, and 500 mg/L. Results showed decline characteristic on methane production with increasing antibiotic concentrations. EC50 values were calculated as 275 mg/L for ES, 219 mg/L for ST, and 130 mg/L for ET. Mixture inhibition of ST and ET combinations were accurately predicted using the concept of independent action, while ES combination resulted in almost the same inhibition with that of single antibiotic response. Inhibition on acetate utilization followed similar trend with methane production inhibition