Carlos G. Dosoretz

This study focused on the evaluation and characterisation of carrier colonisation of a deammonification moving-bed biofilm reactor (dMBBR) at a low carrier-inoculation ratio (≤5%v/v), applying multiple methodologies. The dMBBR (5 L working volume) was filled with Aqwise carriers (50%v/v filling ratio) and fed with synthetic feedstock. Carrier colonisation was differentially tracked using grey colour for new carriers and white colour for pre-colonised seed carriers. The reactor operated for 190 days at a nitrogen loading of 125-140 gN/m³/d. Multivariant heatmap analysis of the process parameters indicated stable deammonification performance from day 85 onwards albeit some occasional malfunctions occurred, with NH₄⁺ and total nitrogen removal rates amounting to 85% and 61%, respectively. Biofilm development on new carriers, evaluated by bulk density measurements via pycnometry, proved to be a reliable, simple, and non-destructive methodology. Anammox of genus Candidatus Brocadia and ammonia oxidising bacteria of genus Nitrosomonas were well established on the new carriers, in line with theoretical and empirical specific activity tests. This multi-parameter evaluation provides a broad insight into deammonification biomass development on the carriers and may assist in shortening the start-up period of dMBBRs.

This study aimed at evaluating the concomitant electrochemical reduction and separation of organic and inorganic model contaminants from water. A highly conductive (40,000 S/m) support free carbon nanotube (CNT) membrane was used as a cathode in a three-electrode electrochemical crossflow membrane filtration system. Diatrizoate (DTZ), a recalcitrant iodinated contrast media; resazurin (RZ), a redox indicator; and hexavalent chromium ion (Cr(VI)), a ‘gold’ standard for characterization of reducing systems, were tested as model contaminants. Voltages 0.6-1.0 V were enough to remove between 90-95% of the three model contaminants tested. Removal of Cr(VI) proceeded by reduction to Cr(III) followed by adsorption onto the cathode, which could be efficiently regenerated (up to 95%) applying reversal (anodic) potential. Preliminary findings applying AC current (0.6-1.5 V, 10 Hz-1kHz) suggest that it could be a feasible approach for detoxification with minimization of membrane clogging. Resazurin was immediately transformed into resorufin to near completion which was in turn further reduced to dihydroresorufin. The reductive transformation of DTZ resulted in almost complete deiodination, leading to accumulation of 3,5-diacetamidobenzoic acid as the main end-product. Although other five secondary transformation products were detected, four of them were fully deiodinated. Concluding, the proposed electrochemical filtration cell equipped with a highly conductive CNT-cathodic membrane can be regarded as a potential technique for water decontamination and effective dehalogenation of organic compounds.

The present study explored bacterial aerobic biodegradation of reduced carbon-contaminants (RCC) in a pilot system mimicking remediation of a saturated aquifer in a permeable reactive biobarrier (PRBB). Bioaugmentation was performed with a pure culture of Pseudomonas putida macro-encapsulated in a cellulose-acetate porous envelope and integrated transversely to the flow trajectory of the fluid in the biobarrier and compared with controls without capsules. The macro-encapsulation technique applied allowed the incorporation of a built-in nutrient core for the slow release of macronutrients, i.e., N,P, instead of exogenous nutrients supply. 3-Chlorophenol (3CP) at a concentration range of 350-500 mg/L was chosen as an RCC model compound. The findings indicate efficient 3CP biodegradation during the PRBB operation with similar degree of transformation (76±2% and 72±2%) and mineralization (55±4% vs. 49±3%) for exogenous and built-in nutrients supply, respectively. The extent of dechlorination in both cases (54±10% vs. 40±2%, respectively) followed mineralization rather than transformation suggesting that Cl^- release took place in late transformation stages. Negligible decontamination was observed in the control system without bioaugmentation. Concluding, tailored PRBB with macro-capsules incorporating a built-in nutrient core to support bacterial growth presents a significant environmental advantage controlling excess nutrients release required in bioremediation of oligotrophic systems.

Increased awareness regarding water pollution and resources conservation due to water scarcity and climate change, combined with intensive urbanization and agricultural production, have raised the need for removal of contaminants of emerging concern (CEC) from treated effluents. CEC include, among others, pharmaceuticals, cleaning and sanitation products, endocrine disrupting compounds, suspected carcinogens, and nanomaterials at trace concentration. Added to this are antibiotic‐resistant bacteria (ARB) and antibiotic‐resistant genes (ARG). Conventional wastewater treatment removes bulk organic contaminants leaving CEC in the effluents. This article discusses the incorporation of advanced treatments such as oxidation processes, adsorption, and tight membrane separation, i.e. reverse osmosis (RO), aimed at removing CEC from effluents. Owing to its generic capability to remove dissolved organic and inorganic contaminants at once, RO appears as the core technology for effluents purification. Besides improvements of existing municipal effluents, changes in conception, management and planning of the urban water systems, e.g. reduction at source and decentralization approaches, are required. Removal of dissolved organic pollutants and mineral contaminants at trace levels cannot be done without consuming energy. The water–energy nexus and related life cycle analyses need to be rethought in terms of environmental and health risks and deterioration of water resources and soils.

Among the factors that obstruct the application of anammox-based technology for nitrogen removal from mainstream municipal wastewater is the water’s high organic loads. We hypothesized that some anammox species can adapt and grow in mainstream wastewater in which a minimal temperature of 13–15 °C is maintained. Using the AMX368F and AMX820R PCR-primers, anammox bacteria were detected in influent wastewater (COD/N ratio > 13) and in the anaerobic, anoxic, and aerobic chambers of a full-scale municipal wastewater treatment plant, reaching 10⁷ copies/g VSS of the16S rRNA gene. Furthermore, anammox activity was demonstrated by ¹⁵N-isotopic tracing. The DNA sequences of clones randomly selected from a clone library were mainly clustered with Candidatus Brocadia flugida in addition to Ca. Brocadia sinica, Ca. Jettenia asiatica, and Ca. Anammoxoglobus propionicus. However, Ca. Brocadia was the only genus detected by high-throughput next-generation sequencing and denaturing gradient gel electrophoresis. The nitrite producers, ammonia-oxidizing archaea and bacteria, were both detected in the influent wastewater and the other chambers, while the nitrite consumers, Nitrospira nitrite oxidizers and the nirS-type denitrifiers, dominated all chambers. The results indicate the occurrence and potential activity of anammox bacteria in mainstream wastewater under certain conditions (proper temperature). The dominance of Brocadia flugida and Anammoxoglobus propionicus suggests a role for volatile fatty acids in selecting the anammox community in wastewater.