ABSTRACT This study assessed the performance of monopolar electrocoagulation (EC) using aluminum electrodes to treat real wastewater generated from cassava starch extraction, a stream characterized by high organic loads, elevated suspended solids, and complex organic matter that can challenge conventional biological treatments. The research was conducted at pilot scale at the La Victoria facility in Sucre, Colombia, between June 2024 and March 2025. A multifactorial experimental design comprising 18 trials was applied, with electric potential (0, 12, 15, and 18 V) and interelectrode distance (2 and 3 cm) as independent variables. The primary response variable was chemical oxygen demand (COD), complemented by biochemical oxygen demand (BOD 5 ), total suspended solids (TSS), turbidity, total phosphorus (TP), and total nitrogen (TN). Among the discrete conditions evaluated, EC3‐15 (3 cm, 15 V) provided the most favorable overall performance, achieving removals of 75.8% for COD, 76.0% for BOD 5 , 57.4% for TSS, approximately 92.0% for turbidity, 72.8% for TP, and 62.7% for TN. EC3‐15 was therefore identified as the best‐performing condition within the experimental domain rather than as a mathematically optimized condition. At 15 V, the estimated specific energy consumption was 9.6 kWh/m 3 , substantially lower than the 17.5 kWh/m 3 estimated at 18 V. Unlike studies relying on synthetic wastewater or high‐energy, multistage reactors, this study shows that a single‐stage EC process operated under moderate electrical conditions can provide an effective decentralized treatment option for highly concentrated agroindustrial effluents. Future work should address sludge valorization and integrate this EC unit as a primary treatment stage before biological polishing.
ABSTRACT The recovery of partial nitritation and anammox (PN/A) process after starvation remains challenging. Substrate limitation disrupts microbial activity and delays the restoration of nitrogen removal performance. Therefore, PN/A nitrogen removal performance was evaluated in a 20‐L laboratory‐scale continuous stirred‐tank reactor (CSTR) containing sponge carriers across four operational phases. The four phases included 3‐month starvation, gradual substrate reintroduction under suspended‐growth conditions, transitional stabilization with sponge media, and attached‐growth recovery under higher nitrogen loading without external acetate supplementation. The laboratory reactor was operated at a nitrogen loading rate of 0.4–0.7 kg N/(m 3 ·d), dissolved oxygen below 0.1 mg/L, and without organic carbon addition. The nitrogen removal efficiency, microbial community composition, and microbial markers of the laboratory‐scale reactor were compared with those of two well‐operated full‐scale systems in Korea and the United States. Total nitrogen removal efficiency exceeded 90% across all three systems when the ammonia‐to‐nitrite ratio (NH₄ + :NO 2 − ) was maintained between 1:1 and 1:1.5 at low BOD/TN ratio of < 0.05. Next‐generation sequencing (Illumina MiSeq, 16S rRNA amplicon profiling at a sequencing depth of 41,120–57,097 reads/sample) was employed to determine the relative abundance of nitrogen‐transforming microbial communities, specifically the anammox group, across the three systems. The results showed that the anammox bacteria in all three systems belonged to Candidatus Brocadia. Following gene‐specific PCR amplification of the anammox community, denaturing gradient gel electrophoresis (DGGE) identified Candidatus Brocadia fulgida. This species exhibits high environmental adaptability and is commonly detected in full‐scale systems operated for > 5 years. Molecular analysis indicated that Candidatus Brocadia fulgida persisted in the system throughout the 3‐month starvation period, facilitating the re‐establishment of the attached‐growth PN/A process. The successful recovery of the laboratory‐scale reactor yielded nitrogen removal performance comparable to that of the full‐scale PN/A systems, demonstrating that the Brocadia group serves as a keystone taxon during process recovery.
ABSTRACT The widespread occurrence of microplastics (MPs) in aquatic environments has become a major environmental concern because conventional wastewater treatment plants primarily retain these particles in sewage sludge rather than achieving their degradation or mineralization. Microbial‐electro‐Fenton systems (MEFSs) have recently emerged as a promising bio‐electro‐chemical advanced oxidation technology that integrates microbial extracellular electron transfer (EET) with electro‐Fenton (EF) chemistry for the in situ generation of hydrogen peroxide (H 2 O 2 ) and hydroxyl radicals (•OH). This review critically evaluates recent advances in carbon‐based electrode engineering, microbial electron transfer mechanisms, molecular regulation of the two‐electron oxygen reduction reaction (2e − ORR), and photo‐bio hybrid enhancement for the treatment of MP‐contaminated wastewater. Emphasis is placed on the distinct roles of anodic biofilms and cathodic electrocatalysts, polymer‐specific degradation pathways, and the successive stages of MP transformation, including surface oxidation, polymer‐chain scission, fragmentation, and mineralization. The influence of reactor configuration, wastewater matrix, and carbon electrode properties on H 2 O 2 electro‐generation, reactive oxygen species production, and degradation efficiency is comprehensively discussed. In addition, current challenges associated with electrode fouling, long‐term durability, real wastewater treatment, scale‐up, and techno‐economic and environmental sustainability are critically assessed. Rather than presenting MEFS as a mature treatment technology, this review identifies the key mechanistic and engineering challenges that must be addressed before practical implementation. Finally, future research priorities are proposed to facilitate the transition of MEFS from laboratory‐scale investigations toward pilot‐scale validation and sustainable wastewater treatment for MP remediation.
ABSTRACT Although integrated wastewater‐fed fisheries in the Ramsar‐designated East Kolkata Wetlands (EKW) provide important ecosystem services, the long‐term spatial and temporal dynamics of microbial attenuation in these managed pond systems remain insufficiently characterized. This study assessed the spatiotemporal dynamics of chlorophyll‐a concentration and culturable bacterial abundance along a canal‐to‐pond transition system over 22 months. Water samples were collected from four fixed locations during 22 sampling months between September 2023 and August 2025 to determine total viable count (TVC), chlorophyll‐a concentration, and chlorophyll‐a‐based trophic state index (TSI). TVC decreased by 79.86%, from a geometric mean of 22,409 colony‐forming units (CFU/mL) at the canal source to 4513 CFU/mL at the distal pond site, and differed significantly among sampling locations ( p < 0.0001). TVC was also significantly higher during the dry season than during the wet season (Mann–Whitney U = 1244.5, p = 0.017). Chlorophyll‐a concentrations did not differ significantly among sampling locations ( p = 0.078), although the mean concentration was 82.8% higher across the three pond stations than at the canal source. Mean TSI values ranged from 47.1 to 52.3 across the sampled gradient. Predictive modeling with Analysis of covariance (ANCOVA) showed that chlorophyll‐a was not a significant predictor of log10‐transformed TVC after accounting for sampling location ( F = 0.48, p = 0.491). These results suggest that site‐associated differences, rather than a statistically detectable chlorophyll‐a effect, are associated with microbial decline within the sampled gradient. Because other physical, chemical, hydraulic, and biological factors were not measured, the observed spatial association cannot be attributed to location alone.
ABSTRACT Wastewater is increasingly not just seen as a burden on the environment but also a source of valuable water, nutrients, energy, carbon, and high value bioproducts for recovery. Integrated biovalorization is a promising strategy to develop conventional wastewater treatment systems into resource generating and circular ones. The review critically assesses the emerging biological platforms and integrated process configurations for wastewater biovalorization (WWB) processes such as anaerobic digestion, microbial fermentation, microalgae‐bacteria systems, microbial electrochemical technologies, biofertilizer production, and wastewater biorefineries: special focus on conversion of organic carbon to volatile fatty acids, biogas, biohydrogen, biopolymer, protein, enzymes, and other value‐added products, recovery of N, P, and water reclamation. The review is focused on the technological performance, resource recovery efficiency, process limitations, environmental sustainability, and commercialization opportunities of the integrated pathways. The potential of membrane technologies, nanomaterials, process intensification, and artificial intelligence and digital monitoring to enhance the process efficiency is also critically discussed. Furthermore, techno‐economic analysis, life cycle effects, contaminant risks, regulatory issues, and scale‐up issues are determined. Hence, future research directions towards smart, decentralized, low carbon, and commercially viable wastewater biorefineries are suggested.
