Removal Of Total Organic Matter Research Articles

A new enrichment strategy of dissimilatory iron-reducing bacteria for remediation of organic-contaminated river sediments: Process, performance, and mechanism

Dissimilatory iron-reducing bacteria (DIRB) have been widely applied to organic matter metabolism in sediments due to their specific biological properties, which are significantly affected by environmental factors. Until now, there has been no systematic study on applying these effects of environmental factors to DIRB enrichment. In this study, we identified the critical environmental factors through RDA, PLS-PM, and correlation analysis and then adjusted the proportion of these factors (C/Fe, C/N, and Fe/S) through single-factor and response surface experiments to enrich DIRB. The performance of the enriched DIRB in carbon metabolism of organic-rich sediments was analyzed by remediation experiment, and the metabolic mechanism was revealed through iron-reducing performance, community structure, and functional genes. The results showed that the carbon, nitrogen, phosphorus, and sulfur were crucial factors influencing the activity of DIRB in river sediments, and the enriched mud-bacteria mixture containing a large amount of DIRB (referred to as “DMB”) obtained by domestication under C/Fe = 0.492 and C/N = 13.659 showed the highest iron reduction rate of 55.51% ± 2.53%. The DMB exhibited better-sustained removal of total organic matter (TOM), which was higher than the control (MB) by 8.81%. Moreover, we discovered that the enriched DIRB: (1) had a better reduction effect on different Fe(III) forms, especially in carbon-limited and iron-limited conditions. (2) increased in abundance and established a beneficial symbiotic relationship with hydrolytic acidifying bacteria. (3) showed an increased abundance of functional pathways associated with organismal systems and signal processing (such as ABC transporters and Translation). These findings revealed the reasons for the improved efficiency of organic matter metabolism.

Induced domestication of humic reduction-denitrification coupled bacteria improved treatment of sediment: Performance, remediation effect, and metabolic mechanisms

The high organic matter in river sediment primarily induces black and odorous rebound. Traditional humic-reducing bacteria demonstrate relatively single metabolic functions and restrain the remediation within complex sediment environments. In addition, Ca(NO3)2 is commonly utilized in synergistic with bioremediation to improve the reducing environment of sediments. In this study, a multifunctional bacterial community with humic reduction-denitrification coupled bacteria was domesticated by the step-feeding strategy in an anaerobic baffle reactor (ABR). The performance, remediation effect, and metabolic mechanisms were analyzed. The results indicated that humic-reducing bacteria (HRB) and denitrifying-humic-reducing bacteria (DF/HRB) have quinone-reduction and denitrification capabilities. The synergistic effect of DF/HRBs and Ca(NO3)2 was superior to HRBs and Ca(NO3)2 on the removal of total organic matter(TOM). Microbial community structure analysis revealed an enhanced relative abundance of denitrification and humic-reducing bacteria (e.g., Thauera, Pseudomonas, Sulfurospirillum, Desulfovibrio, Geobacter) in the DF/HRB, resulting in a superior synergistic effect of DF/HRBs with Ca(NO3)2. This work helps to present an innovative approach to domesticate humic-reducing bacteria suited for the remediation environment effectively. It also expands the application of humic-reducing bacteria for in-situ anaerobic remediation of river sediments.

Biodegradation of TOC by Nano‐Fe2O3 Modified SMFC and Its Potential Environmental Effects**

AbstractIn this paper, sediment microbial fuel cell (SMFC) with nano‐Fe2O3 modified anode was investigated to enhance in‐situ remediation. Results showed that the modification led to higher removal of total organic matter (TOC) after 50 days. Anodic microbial community was further analyzed. It was found that the decrease of relative abundance of exoelectrogens and the suppression of methanogens led to the reduction of the power generation in SMFC with modified anode. Longilinea was one of key bacteria regarding TOC degradation. Besides, potential environmental effects resulting from SMFC and nano‐Fe2O3 modification were also discussed. The competition of exoelectrogens with methanogens for nutrient potentially resulted in the reduction of methane emission. The SMFC system could inhibit the growth of fecal bacteria and the nano‐Fe2O3 modified anode had stronger inhibitory effect, which further reduce the risks induced by fecal bacteria to human health. The modification could further maintain the biodiversity of eucaryon and achieve higher ecosystem stability.

Purification Efficiency and Influencing Factors of Combined Bio-filters for Aquaculture Wastewater

As an effective technology for wastewater treatment, bio-filter has been widely used. Nevertheless, there is still a lack of systematic report on purification efficiency and influencing factors of combined bio-filters. To this end, a novel combined system that consisted of aerated vertical-flow filter (AVF) followed by baffled horizontal-flow filter (BHF) was designed. After setting a series of hydraulic loading rates (131, 94 and 60 mm·d-1) and diversion ratios (8:2、6:4、4:6), we comprehensively assessed the impact of running condition adjustment on treatment performance by multiple statistical analyses. The results showed that, the average removal rates of organic matter, ammonia nitrogen and dissolved nitrogen in AVF were all above 80%, while the average removal rates of ammonia nitrogen, total nitrogen and dissolved nitrogen in BHF were all below 40%. Different running conditions had a significant (P<0.05) impact on treatment performance. Meanwhile, there were significant differences in purification efficiency between the two different kinds of filters. Oxidative degradation was one of the main ways to remove organic matter in the two kinds of filters. There were obvious nitrification and denitrification processes within the two kinds of filters. Nitrification followed by denitrification was the main way to remove total nitrogen since ammonium occupied the most portion of total nitrogen in the synthetic wastewater. Meanwhile, the intensity of nitrification and denitrification in AVF was obviously higher than that in BHF. Phosphorus removal was mainly controlled by hydraulic loading rate, temperature, dissolved oxygen, organic matter, etc. This might indicate that microbial absorption was one of the main ways to remove phosphorus for the two filters. Compared to the sole AVF, the removal of total organic matter and total phosphorus in the combined system was increased by 4.4% and 23.2%, respectively, but the removal of total nitrogen was reduced by 12.1%. Reducing the diversion ratio was helpful to improve the denitrification intensity in BHF. However, due to the introduction of excessive ammonia from the raw wastewater, as well as the limited nitrification capacity in BHF, the removal rate of total nitrogen for the combined system was decreased. Therefore, according to the composition of treated raw wastewater, the control of appropriate diversion ratio, residence time and redox conditions inside the filter bed was the key to enhance the overall performance of the combined system.

Examination of protein degradation in continuous flow, microbial electrolysis cells treating fermentation wastewater

Cellulose fermentation wastewaters (FWWs) contain short chain volatile fatty acids and alcohols, but they also have high concentrations of proteins. Hydrogen gas production from FWW was examined using continuous flow microbial electrolysis cells (MECs), with a focus on fate of the protein. H2 production rates were 0.49±0.05m3/m3-d for the FWW, compared to 0.63±0.02m3/m3-d using a synthetic wastewater containing only acetate (applied potential of 0.9V). Total organic matter removal was 76±6% for the FWW, compared to 87±5% for acetate. The MEC effluent became relatively enriched in protein (69%) compared to that in the original FWW (19%). Protein was completely removed using higher applied voltages (1.0 or 1.2V), but current generation was erratic due to more positive anode potentials (−113±38mV, Eap=1.2V; −338±38mV, 1.0V; −0.426±4mV, 0.9V). Bacteria on the anodes with FWW were primarily Deltaproteobacteria, while Archaea were predominantly Methanobacterium.

Membrane bioreactor for the treatment of pharmaceutical wastewater containing corticosteroids

Efficient removal of total organic matter, ammonia and four target corticosteroids, levonogestrel (Levo), bethametasone valerate (Betha-V), bethametasone dipropionate (Betha-D) and medroxyprogesterone acetate (Medro), was achieved in a laboratory-scale submerged membrane bioreactor (MBR) treating wastewater from a pharmaceutical industry. MBR was operated for a period of 20weeks under a constant flux of 2.87L h−1 m−2 without substantial membrane fouling. Total organic matter removal, measured in terms of chemical oxygen demand (COD), was on average over 99%. Regarding nutrients, 99% of the initial ammonia and 40% of phosphorous were eliminated. The industrial wastewater was spiked with four target corticosteroids at a final concentration of 100μg L−1 in order to assess their elimination. Chemical analysis of MBR effluent revealed that all corticosteroids were removed at percentages higher than 93% in all the cases.

Inert Soluble Organic Matter in Return Flow from Sludge Treatment Process and Its Control by Coagulation

In the wastewater reclamation plants, one of the important parameters is inert soluble organic matter for controlling fouling in the membrane processes. We studied the fate of inert soluble organic matter, SI, by field studies in municipal wastewater treatment plants including a sludge treatment train and a lab-scale experiment on coagulation of the sludge and the return flow. The filed survey showed: (1) the thermal treatment unit produced the SI load, about 60% of the total SI load to the water treatment train; (2) the sludge treatment trains consisted of thickening + chemical conditioning + filter press or the train with thickening + anaerobic digestion + filter press produced about 20% of the total SI load to the water treatment train; (3) a remarkable decrease in SI concentration occurred in chemical conditioning and the dewatering process of digested sludge, but in the conditioning of raw thickened sludge, the SI concentration was increased. The jar test using thickener overflow and digester supernatant showed: (4) in the coagulation of the thickener overflow, low pH condition gives higher performance in SI reduction, and a higher dose of Poly Silicate Iron (PSI) gives the higher removal percentage; (5) as to the digester supernatant, SI reduction strongly depends on pH rather than coagulant dosage and the removal performance of SI is far smaller than the removal of total organic matter.

Use of a lux‐modified bacterial biosensor to identify constraints to bioremediation of btex‐contaminated sites

AbstractSediment and groundwater samples obtained from a benzene, toluene, ethylbenzene, and xylene (BTEX)‐contaminated site were screened, using a bioluminescence‐based (lux gene‐marked) bacterial biosensor, to identify constraints to site remediation. Through a series of sample manipulations and linked biosensor responses, constraints to BTEX remediation such as adverse pH, presence of nonvolatile organic contaminants, and the presence of heavy metals were investigated. Conventional chemical analysis (gas chromatography, inductively coupled plasma mass spectroscopy) was used to confirm the reliable performance of the biosensor and to identify its potential contribution to site management to ensure effective remediation. The toxicity results of the biosensor were expressed in % maximum bioluminescence calculated against a blank of double deionized water with pH adjusted to 5.5. Untreated samples caused reductions in percentage bioluminescence from 10 to 95%. Water sample W1, containing a total BTEX concentration of 30,595 μg/L caused the highest decrease in bioluminescence (5.78%). This toxicity was significantly reduced after elimination of volatile organic compounds (VOCs) (42.01%) and bioluminescence was further increased to 87.80% after removal of total organic matter. This suggested that VOCs were not the only toxic organopollutants present. Water samples giving high values of bioluminescence contained BTEX concentrations of 17 to 31 μg/L.