Performance and microbial community profiles in pilot-scale biofilter for ammonia, iron and manganese removal at different dissolved oxygen concentrations

Depth profiles of biological aerated contactors: Characterizing microbial activity treating reduced contaminants

The biological treatment process consisting of an aerated contactor and filter is effective for groundwaters containing elevated ammonia and other reduced contaminants, including iron, manganese, arsenic, and methane. Depth profiles characterizing microbial activity across aerated contactors are lacking. A 1-year pilot study comparing gravel- and ceramic-packed contactors was conducted, and media depth profile samples were collected at the conclusion of the study. Media and water samples also were collected from pilot-scale aerated contactors at 4 other water systems. Water quality, media surface metals concentrations, and a suite of biofilm parameters were analyzed. Media surface metals concentrations were greatest at the influent end. ATP concentrations, extracellular polymeric substances, and extracellular enzyme activities tended to be similar across depth. Bacteria and functional genes involved in contaminant oxidation co-occurred and tended to decrease across depth, but were not correlated to the media metals concentration. Microbial community composition changed with depth, and the diversity either decreased or remained similar. The microbial activity profiles through aerated contactors differed from what is typically reported for groundwater biofilters, suggesting that the different reactor flow and dissolved oxygen profiles impacted the microbial community.

Efficient utilization of biogenic manganese oxides in bioaugmentation columns for remediation of thallium(I) contaminated groundwater

Little attention has been paid to the in situ-generated biogenic manganese oxides (BMnOx) for practical implementation in continuous groundwater remediation systems. The enrichment effects of manganese oxidizing bacteria (MOB) in bioaugmentation columns and the in situ-generated BMnOx for continuous thallium(I) (Tl(I)) removal from groundwater were investigated. Results indicated that Pseudomonas Putida MnB1 (strain MnB1) attached on the groundwater sediments (GS) can achieve a maximum of 97.37 % Mn(II) oxidation and generate 29.6 mg/L BMnOx, which was superior than that of traditional quartz sand (QS). The in situ-generated BMnOx in MOB_GS column effectively removed 10-100 μg/L Tl(I) under the interference of high concentrations of Fe(II) and Mn(II) in groundwater. Distinctive microbial enrichment effects occurred in the bioaugmentation columns under the competition of indigenous microbes in groundwater. The release of Mn(II) from the BMnOx inhibited with the decrease in Tl(I) removal efficiency. XAFS analysis revealed Tl(I) was effectively adsorbed by BMnOx and Mn-O octahedra with Tl-O tetrahedral coordination existed in BMnOx. This study provides an in-depth understanding of the in situ-generated BMnOx for the Tl(I) removal and contributes to the application of BMnOx in groundwater remediation.

Mixotrophy broadens the ecological niche range of the iron oxidizer Sideroxydans sp. CL21 isolated from an iron-rich peatland

Sideroxydans sp. CL21 is a microaerobic, acid-tolerant Fe(II)-oxidizer, isolated from the Schlöppnerbrunnen fen. Since the genome size of Sideroxydans sp. CL21 is 21% larger than that of the neutrophilic Sideroxydans lithotrophicus ES-1, we hypothesized that strain CL21 contains additional metabolic traits to thrive in the fen. The common genomic content of both strains contains homologs of the putative Fe(II) oxidation genes, mtoAB and cyc2. A large part of the accessory genome in strain CL21 contains genes linked to utilization of alternative electron donors, including NiFe uptake hydrogenases, and genes encoding lactate uptake and utilization proteins, motility and biofilm formation, transposable elements, and pH homeostasis mechanisms. Next, we incubated the strain in different combinations of electron donors and characterized the fen microbial communities. Sideroxydans spp. comprised 3.33% and 3.94% of the total relative abundance in the peatland soil and peatland water, respectively. Incubation results indicate Sideroxydans sp. CL21 uses H2 and thiosulfate, while lactate only enhances growth when combined with Fe, H2, or thiosulfate. Rates of H2 utilization were highest in combination with other substrates. Thus, Sideroxydans sp. CL21 is a mixotroph, growing best by simultaneously using substrate combinations, which helps to thrive in dynamic and complex habitats.

A review on the use of chitosan and chitosan derivatives as the bio-adsorbents for the water treatment: Removal of nitrogen-containing pollutants

Chitosan and its derivatives have been widely used as the adsorbents for different types of water pollutants. This review paper lists various physically and chemically modified chitosan-based adsorbents such as chitosan beads, cross-linked chitosan, chitosan-polymer composites, chitosan-inorganic material composites, and chitosan-metal complexes for the removal of nitrogen-containing pollutants (nitrate, nitrite, ammonia, and ammonium ions) from aqueous solutions. It covers preparation strategies, the effect of modification on adsorbent structure, and the impact of adsorption variables using batch and fixed-bed column studies. In addition to demonstrating the applications of chitosan and its derivatives in the removal of nitrogenous pollutants from water, it helps researchers understand the influence of modification of chitosan on its adsorption capacity as well as physical and chemical properties.

Advanced treatment of dye wastewater using a novel integrative Fenton-like/MnO2-filled upward flow biological filter bed system equipped with modified ceramsite

The deposal of residual hydrogen peroxide (H₂O₂) in Fenton-like system and the requirement of oxygen in bioreactor are essential parts for the treatment of integrative Fenton-like/bioreactor. A novel low-cost integrative Fenton-like and MnO₂-filled upward flow biological filter bed (Fenton-like/MBFB) equipped with the modified ceramsite was constructed to evaluate the main properties and catalytic activity of modified ceramsite, and the optimal conditions of integrative system and compare integrative and traditional systems. In this study, the Fenton-like reactor with modified ceramsite had higher catalytic ability whose Acid Orange 7 (AO7) degradation efficiency reached to 79.3% due to large surface area and high porosity, compared with that with raw ceramsite (44.3%). Furthermore, total utilization efficiency of H₂O₂ in integrative system (from 32.41% to 53.51%) and removal efficiencies of COD and AO7 were remarkably improved, which would effectively decrease the waste of H₂O₂ and the setting of regulation pool and aeration tank. Thus, the integrative system can save 0.51 CNY/m³ in construction cost and 0.21 CNY/m³ in operating cost. The average COD removal efficiency, AO7 degradation efficiency and effluent DO concentration were achieved to 64.8%, 79.5% and 9.3 mg/L respectively in integrative system were achieved in integrative system during sixty successive runs. Also, the potential degradation pathway of contaminants was also proposed according to the OH-enhanced at Fenton-like reactor due to catalyst and adsorption of modified ceramsite and the removal of microorganisms and modified ceramsite for contaminants at MBFB. This study demonstrated the feasibility of integrative Fenton-like/MBFB filled with modified ceramsite for simultaneously decreasing operational cost and complexity and enhancing removal efficiency, thus provided a one-step alternative for refractory dye wastewater.

Chitosan Modified Zeolite Molecular Sieve Particles as a Filter for Ammonium Nitrogen Removal from Water

Drinking water containing a high amount of ammonium-nitrogen (NH₄⁺-N) is not effectively removed by conventional treatment processes and can cause eutrophication. In this research, a composite adsorbent based on chitosan crosslink with zeolite molecular sieve (CTS-ZMS) was prepared for NH₄⁺-N removal through dynamic adsorption filter experiments. Effect of bed depth (30, 50 and 70 cm), flow rate (32, 49 and 65 mL/min), initial pH value (4.5, 6.5 and 8.5) and influent NH₄⁺-N concentration (3, 5 and 7 mg/L) was examined by using a filter column packed with CTS-ZMS particles. The Thomas model was applied to study the breakthrough curves and adsorption capacity. The optimal process parameters of the aforementioned factors were obtained at bed depth of 70 cm, flow rate of 32 mL/min, pH of 6.5 and initial NH₄⁺-N concentration of 7 mg/L. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS) and Fourier Transform Infrared Spectroscopy (FTIR) were investigated to analyze the structure and morphology of the CTS-ZMS adsorbents before and after 3 months running. The EDS and FTIR results showed Na⁺ and the active functional groups of -OH, -NH₂ and -COO⁻ on CTS-ZMS adsorbent particles reacted with ammonium nitrogen. The results of this study supported the use of CTS-ZMS to improve drinking water filtration processes by increasing ammonium nitrogen reductions.