Kalu I. Ekpeghere

Full-scale biological treatment of tannery wastewater using the novel microbial consortium BM-S-1

In order to develop a more effective and eco-friendly treatment technology, a full-scale tannery wastewater treatment plant with a sludge digestion system was augmented with a novel microbial consortium (BM-S-1). The aim of this study was to determine if the BM-S-1 could successfully treat the tannery wastewater in a full-scale treatment system without chemical pretreatment and to investigate effect of the augmentation on sludge production. Chemical oxygen demand (COD), total nitrogen (TN), total phosphorus (TP), chromium (Cr) and mixed liquor suspended solids (MLSS) were measured to monitor treated water quality and treatment efficiency. Microbial community structures in the treatment were also examined using pyrosequencing analysis of 16S rRNA gene and quantitative PCR (qPCR) of the nitrous oxide reductase gene (nosZ). The removal efficiencies of COD, TN, TP, and Cr were estimated to be 98.3%, 98.6%, 93.6%, and 88.5%, respectively, while the system without a continuous augmentation was broken down. The pyrosequencing analysis showed Brachymonas denitrificans to be the most dominant microbial population in the buffering tank (B; 37.5%). Potential polymeric substance degraders (Clostridia), sulfate reducers (Desulfuromonas palmitatis), and sulfur oxidizers (uncultured Thiobacillus) were dominant in the sludge digestion (SD) tank. The denitrifiers assayed by nosZ qPCR were dominant in B and SD. These microbial communities appeared to play important roles in removing nutrients and odor, and reducing sludge in the wastewater treatment plant without chemical pretreatment.

Metagenomic insight of nitrogen metabolism in a tannery wastewater treatment plant bioaugmented with the microbial consortium BM-S-1.

ABSTRACT Nitrogen (N) removal in a tannery wastewater treatment plant was significantly enhanced by the bioaugmentation of the novel consortium BM-S-1. In order to identify dominant taxa responsible for N metabolisms in the different stages of the treatment process, Illumina MiSeq Sequencer was used to conduct metagenome sequencing of the microbial communities in the different stages of treatment system, including influent (I), buffering (B), primary aeration (PA), secondary aeration (SA) and sludge digestion (SD). Based on MG-RAST analysis, the dominant phyla were Proteobacteria, Bacteroidetes and Firmicutes in B, PA, SA and SD, whereas Firmicutes was the most dominant in I before augmentation. The augmentation increased the abundance of the denitrification genes found in the genera such as Ralstonia (nirS, norB and nosZ), Pseudomonas (narG, nirS and norB) and Escherichia (narG) in B and PA. In addition, Bacteroides, Geobacter, Porphyromonasand Wolinella carrying nrfA gene encoding dissimilatory nitrate reduction to ammonium were abundantly present in B and PA. This was corroborated with the higher total N removal in these two stages. Thus, metagenomic analysis was able to identify the dominant taxa responsible for dissimilatory N metabolisms in the tannery wastewater treatment system undergoing bioaugmentation. This metagenomic insight into the nitrogen metabolism will contribute to a successful monitoring and operation of the eco-friendly tannery wastewater treatment system.

Functions of effective microorganisms in bioremediation of the contaminated harbor sediments

The aim of this study was to apply loess balls containing effective microorganisms (EM) to the remediation of contaminated harbor sediments, and to thereby elucidate the functions of EM in remediation. Changes in physicochemical, biochemical, and microbiological parameters were measured to monitor the remediation process at a laboratory scale. Treatment with high concentrations of EM stock culture and EM loess balls (4%), and a low concentration of EM loess balls (0.1%) that contained molasses (0.05%) contributed to more rapid removal of malodor. Acetic acid, propionic acid, valeric acid, caponic acid, and lactic acid were rapidly removed in the presence of molasses (0.05% w/w) as a carbon nutrient source, indicating enhanced EM activity by amendment with molasses. Fermentation of molasses by EM showed that more acetic acid was produced compared with other organic acids, and that the majority of organic acids were eventually converted to acetate via intermediate metabolites. Sediment bioremediation tests showed there was no significant difference in eubacterial density with the control and the treatments. However, the density of a Lactobacillus sp. in sediments treated with 0.1% and 4.0% EM loess balls was significantly higher than the control, which indicated the bioaugmentation effect of EM loess balls in the polluted sediments. Treatment with EM loess balls and an appropriate amount of molasses, or other nutrients, will facilitate the remediation of polluted marine sediments by malodor removal, via EM degradation or utilization of offensive organic acids. To our knowledge, this is the first study to remediate contaminated marine (harbor) sediments using EM loess balls and to understand EM function during the bioaugmentation process, both in terms of organic acid metabolism and the dynamics of the engineered microbial community.