Search Results (251)

The uMlazi River receives effluents from wastewater work before feeding the Shongweni Dam. However, local communities are consuming fish from this dam for protein supplements. This study was undertaken to investigate the metal concentrations in the water and sediment, the general health of Coptodon rendalli and Oreochromis mossambicus, and metal bioaccumulation. Sampling was conducted during the dry (July–August) and wet seasons (November and December) in 2021. Water was sampled using acid-pre-treated sampling bottles, whereas sediment was collected using the Van Veen grab at the inflow, middle, and dam wall. Fish were collected, and their tissues were digested using aqua regia. Metal concentrations were measured using inductively coupled plasma optical emission spectroscopy (ICP-OES). This data manuscript reports the physical parameters of the water and concentrations of antimony, arsenic, cadmium, copper, iron, manganese, lead, selenium, and strontium in the water and sediment from the Shongweni Dam. Moreover, the fish morphometric data and metal concentrations observed in the muscle are also presented. This data could be used as baseline information on metal concentrations in the Shongweni Dam. Moreover, it provides insight into the potential impact of wastewater effluents on metal increases in freshwater bodies. Full article

This work studies and analyzes the transition from a linear to a circular economy through wastewater treatment and resource recovery. As wastewater volumes grow, sustainable management becomes critical. This study highlights the reuse of treated effluent, beneficial sludge utilization, and energy generation via anaerobic digestion. Wastewater treatment plants should be envisioned as hubs for recovering water, materials, and energy, rather than disposal facilities. Emphasizing resource efficiency, the circular economy approach offers viable solutions to challenges related to resource scarcity, climate change, and ecological impact. Full article

This study evaluated the effects of different doses of limonene essential oil (LEO) and a blend of cinnamaldehyde and carvacrol (BCC) on the fermentative quality and chemical–bromatological composition of total mixed ration (TMR) silages. Two independent trials were conducted, each focused on one additive, using a completely randomized design with four treatments (0, 200, 400, and 600 mg/kg of dry matter), replicated across two seasons (summer and autumn), with five replicates per treatment per season. The silages were assessed for their chemical composition, fermentation profile, aerobic stability (AS), and storage losses. In the LEO trial, the dry matter (DM) content increased significantly by 0.047% for each mg/kg added. Dry matter recovery (DMR) peaked at 97.9% at 473 mg/kg (p < 0.01), while lactic acid (LA) production reached 5.87% DM at 456 mg/kg. Ethanol concentrations decreased to 0.13% DM at 392 mg/kg (p = 0.04). The highest AS value (114 h) was observed at 203.7 mg/kg, but AS declined slightly at the highest LEO dose (600 mg/kg). No significant effects were observed for the pH, neutral detergent fiber (NDF), acid detergent fiber (ADF), crude protein (CP), or non-fiber carbohydrates (NFCs). In the BCC trial, DMR reached 98.2% at 548 mg/kg (p < 0.001), and effluent losses decreased by approximately 20 kg/ton DM. LA production peaked at 6.41% DM at 412 mg/kg (p < 0.001), and AS reached 131 h at 359 mg/kg. BCC increased NDF (from 23.27% to 27.73%) and ADF (from 35.13% to 41.20%) linearly, while NFCs and the total digestible nutrients (TDN) decreased by 0.0007% and 0.039% per mg of BCC, respectively. In conclusion, both additives improved the fermentation efficiency by increasing LA and reducing losses. LEO was more effective for DM retention and ethanol reduction, while BCC improved DMR and AS, with distinct effects on fiber and energy fractions. Full article

Industrial wastewater management remains a critical barrier to achieving Sustainable Development Goal 6 (SDG 6) in many developing countries, where regulatory frameworks exist but affordable and scalable treatment solutions are lacking. In Pakistan, the textile sector is a leading polluter, with untreated effluents routinely discharged into rivers and agricultural lands despite stringent National Environmental Quality Standards (NEQS). This study presents a pilot-scale case from Faisalabad’s Khurrianwala industrial zone, where a decentralized, nature-based bioreactor was piloted to bridge the gap between policy and practice. The system integrates four treatment stages—anaerobic digestion (AD), floating treatment wetland (FTW), constructed wetland (CW), and sand filtration (SF)—and was further intensified via nutrient amendment, aeration, and bioaugmentation with three locally isolated bacterial strains (Acinetobacter junii NT-15, Pseudomonas indoloxydans NT-38, and Rhodococcus sp. NT-39). The fully intensified configuration achieved substantial reductions in total dissolved solids (TDS) (46%), total suspended solids (TSS) (51%), chemical oxygen demand (COD) (91%), biochemical oxygen demand (BOD) (94%), nutrients, nitrogen (N), and phosphorus (P) (86%), sulfate (26%), and chloride (41%). It also removed 95% iron (Fe), 87% cadmium (Cd), 57% lead (Pb), and 50% copper (Cu) from the effluent. The bacterial inoculants persist in the system and colonize the plant roots, contributing to stable bioremediation. The treated effluent met the national environmental quality standards (NEQS) discharge limits, confirming the system’s regulatory and ecological viability. This case study demonstrates how nature-based systems, when scientifically intensified, can deliver high-performance wastewater treatment in industrial zones with limited infrastructure—offering a replicable model for sustainable, SDG-aligned pollution control in the Global South. Full article

This study investigated the treatment of unsterilized, undiluted, and unfiltered liquid digestate in a large-scale photobioreactor over a period of 33 weeks using a consortium of microalgae and bacteria. The generated biomass was analyzed for a wide spectrum of value-added compounds. The impact of organic loading rates (OLR) on the microbial culture was determined, and the influence of the biomass storage method on its qualitative composition was also analyzed. The experiment showed optimal growth of microalgae at OLR = 0.1 gCOD/L/day (where COD is Chemical Oxygen Demand), while a higher OLR value led to culture destabilization. Microglena sp., an algae not commonly applied for digestate treatment, showed low tolerance to changes in process conditions (OLR increase) but high readaptation potential when the OLR was lowered to its initial value. Significant changes in the microbial community were observed during the treatment. In Phases 1 and 2, Desmodesmus subspicatus and Actinomycetota phylum dominated in the community, while in Phase 3, Microglena sp. and Firmicutes were the most abundant. Total nitrogen, orthophosphates, and soluble COD were reduced by 89–99%. The biomass storage method had a notable impact on the content of lipids, fatty acids, and pigments. The protein amount was 32.75–33.59% of total solids (TS), while total lipid content was 15.76–19.00% TS, with stearic and palmitic acid being dominant. The effect of the storage regime on the potential biomass valorization was also discussed. Full article

The ongoing global population growth and the corresponding rise in energy demand have contributed to increased greenhouse gas (GHG) emissions. The integration of alternative, locally sourced energy solutions such as biogas presents a promising strategy to partially offset conventional energy consumption. In this context, countries like Colombia—characterized by a high availability of organic waste such as palm oil mill effluent (POME), rice straw, and pig manure—have the potential to harness these residues for biogas production. This study integrates experimental assays of anaerobic co-digestion tests with the spatial analysis of substrate distribution through GIS tools, enabling the identification of optimal regions for biogas production. Methane yields reached 412 mL CH₄/g VS, comparable or superior to those reported in similar studies. In addition to laboratory assays, Geographic Information System (GIS) tools were used to generate a weighted heatmap index based on feedstock availability (POME, rice straw, pig manure) across 40 municipalities in Colombia. This integrated approach supports decentralized renewable energy planning and helps identify optimal locations for biogas plant development. Full article

An integrated process scheme is developed for valorizing filtered liquid digestates (FLD) from an industrial anaerobic digestion (AD) plant treating dairy-processing effluents with relatively low nutrient concentrations. The process scheme involves FLD treatment by nanofiltration (NF) membranes, followed by struvite recovery from the NF-retentate. An NF pilot unit (designed for this purpose) is combined with a state-of-the-art NF/RO process simulator. Validation of simulator results with pilot data enables reliable predictions required for scaling up NF systems. The NF permeate meets the standards for restricted irrigation and/or reuse. Considering the significant nutrient concentrations in the NF retentate (i.e., ~500 mg/L NH4-N, ~230 mg/L PO4-P), struvite recovery/precipitation is investigated, including determination of near-optimal processing conditions. Maximum removal of nutrients, through production of struvite-rich precipitate, is obtained at a molar ratio of NH₄:Mg:PO₄ = 1:1.5:1.5 and pH = 10 in the treated stream, attained through the addition of Κ₂HPO₄, ΜgCl₂·6H₂O, and NaOH. Furthermore, almost complete struvite precipitation is achieved within ~30 min, whereas precipitate/solid drying at modest/ambient temperature is appropriate to avoid struvite degradation. Under the aforementioned conditions, a significant amount of dry precipitate is obtained, i.e., ~12 g dry mass per L of treated retentate, including crystalline struvite. The approach taken and the obtained positive results provide a firm basis for further development of this integrated process scheme towards sustainable large-scale applications. Full article

This study explores the feasibility of producing biohydrogen from winery wastewater using a dual-chamber microbial electrolysis cell (MEC). A mixed microbial consortium pre-adapted to heavy-metal environments and enriched with Geobacter sulfurreducens was anaerobically cultivated from diverse waste streams. Over 5000 h of development, the MEC system was progressively adapted to winery wastewater, enabling long-term electrochemical stability and high organic matter degradation. Upon winery wastewater addition (5% v/v), the system achieved a sustained hydrogen production rate of (0.7 ± 0.3) L H₂ L⁻¹ d⁻¹, with an average current density of (60 ± 4) A m⁻³, and COD removal efficiency exceeding 55%, highlighting the system’s resilience despite the presence of inhibitory compounds. Coulombic efficiency and cathodic hydrogen recovery reached (75 ± 4)% and (87 ± 5)%, respectively. Electrochemical impedance spectroscopy provided mechanistic insight into charge transfer and biofilm development, correlating resistive parameters with biological adaptation. These findings demonstrate the potential of MECs to simultaneously treat agro-industrial wastewaters and recover energy in the form of hydrogen, supporting circular resource management strategies. Full article

Palm oil production generates substantial underutilized biomass wastes, including empty fruit bunches, fiber, palm kernel shells, and palm oil mill effluent (POME). Waste-to-energy systems offer a viable pathway to convert these residues into electricity and fertilizer, supporting circular economy goals and sustainability targets. This study takes an example of palm oil waste from the Indragiri Hulu region in Riau Province in Indonesia. It develops a multi-objective optimization framework to evaluate palm oil mill WtE systems from economic, environmental, and energy output. Three scenarios are analyzed: maximal profit (MP), maximal profit with carbon tax (MPCT), and all waste processing (AWP). The MP scenario favors high-return technologies such as gasification and incineration, leading to significant greenhouse gas emissions. The MPCT scenario favors lower-emission technologies like composting and excludes high-emission, low-profit options such as POME digestion. In contrast, the AWP scenario mandates the processing of all wastes, leading to the lowest profits and the highest emissions among all scenarios. The sensitivity analysis reveals that POME processing is not feasible when electricity prices are below the government-set rate, but becomes viable once prices exceed this threshold. These findings offer valuable insights for companies and policymakers seeking to develop and implement effective strategies for optimal waste utilization. Full article

An integrated hybrid system was developed, incorporating sedimentation, anaerobic digestion, biological filtration, and a two-stage hybrid subsurface flow constructed wetland, horizontal subsurface flow constructed wetland (HSSFCW) and vertical subsurface flow constructed wetland (VSSFCW), to treat rural sewage in southern Jiangsu. To optimize nitrogen and phosphorus removal, the potential of six readily accessible industrial and agricultural waste byproducts—including plastic fiber (PF), hollow brick crumbs (BC), blast furnace steel slag (BFS), a zeolite–blast furnace steel slag composite (ZBFS), zeolite (Zeo), and soil—was systematically evaluated individually as substrates in vertical subsurface flow constructed wetlands (VSSFCWs) under varying hydraulic retention times (HRTs, 0–120 h). The synergy among substrates, plants, and microbes, coupled with the effects of hydraulic retention time (HRT) on pollutant degradation performance, was clarified. Results showed BFS achieved optimal comprehensive pollutant removal efficiencies (97.1% NH₄⁺-N, 76.6% TN, 89.7% TP, 71.0% COD) at HRT = 12 h, while zeolite excelled in NH₄⁺-N/TP removal (99.5%/94.5%) and zeolite–BFS specializing in COD reduction (80.6%). System-wide microbial analysis revealed organic load (sludges from the sedimentation tank [ST] and anaerobic tanks [ATs]), substrate type, and rhizosphere effects critically shaped community structure, driving specialized pathways like sulfur autotrophic denitrification (Nitrospira) and iron-mediated phosphorus removal. Annual engineering validation demonstrated that the optimized strategy of “pretreatment unit for phosphorus control—vertical wetland for enhanced nitrogen removal” achieved stable effluent quality compliance with Grade 1-A standard for rural domestic sewage discharge after treatment facilities, without the addition of external carbon sources or exogenous microbial inoculants. This low-carbon operation and long-term stability position it as an alternative to energy-intensive activated sludge or membrane-based systems in resource-limited settings. Full article

The present study investigates a two-stage process aimed at producing biogas from food waste leachates (FWL) through an experimental approach. The first stage involves biohydrogen production via dark fermentation (DF), while the second focuses on biomethane production through anaerobic digestion (AD). The substrate consists of leachates derived from fruit and vegetable waste, which are introduced into two continuous stirred-tank reactors (CSTR1) with two different inoculum-to-substrate ratios (ISR). Dark fermentation occurs in these reactors. The effluent from the CSTRs is then fed into two additional reactors for methanogenesis. All reactors operated under mesophilic conditions. During the DF stage, hydrogen yields were relatively low, with a maximum of 8.2 NmL H₂/g VS added (ISR = 0.3) and 6.1 NmL H₂/g VS added (ISR = 0.5). These results were attributed to limited biodegradation of volatile solids (VS), which reached only 21.9% and 23.6% in each respective assay. Similarly, the removal of organic matter was modest. In contrast, the AD stage demonstrated more robust methane production, achieving yields of 275.2 NmL CH₄/g VS added (ISR = 0.3) and 277.5 NmL CH₄/g VS added (ISR = 0.5). The system exhibited significant organic matter degradation, with VS biodegradability reaching 66%, and COD removal efficiencies of 50.8% (ISR = 0.3) and 60.1% (ISR = 0.5). The primary focus of the study was to monitor and quantify the production of the two biofuels, biohydrogen and biomethane. In conclusion, this study provides an assessment of the two biochemical conversion pathways, detailing the generation of two valuable and utilizable gaseous products. This research examines the process-specific operational conditions governing gas production, with a focus on optimizing process parameters to enhance yield and overall efficiency. Full article

The construction of an anaerobic digester coupled with post-digestion low-level aeration for agricultural wastewater treatment is described. The digester employs underwater speakers to accelerate the anaerobic digestion process while retaining solids to reduce the strength of the effluent. The effluent is sent to a holding tank and fed at a low flow rate to an aeration tank to effect partial nitrification of the wastewater. The outlet of this tank is sent to a settling tank to retain biomass that developed in the aeration tank, and the effluent is sent to a small constructed wetland to further reduce wastewater nitrogen and phosphorus. The wetland was planted with the broadleaf cattail, Typha latifolia, and hence led to the formation of a retention basin. The system has reduced energy consumption due to the use of underwater sonic treatment and low-level aeration that is not designed to achieve full nitrification/denitrification but rather to achieve a mixture of ammonium, nitrite, and nitrate that might foster the development of a consortium of organisms (i.e., nitrifiers and Anammox bacteria) that can remediate wastewater ammonium at low cost. The system is meant to serve as a complex where various technologies and practices can be evaluated to improve the treatment of agricultural wastewater. Preliminary data from the system are presented. Full article

Palm oil mill effluent (POME), a byproduct of palm oil processing, has substantial resource recovery potential. Its rich biodegradable content supports methane (CH₄) production via anaerobic digestion, enabling renewable energy generation. Additionally, the significant water content of POME can be reclaimed for use in boiler feed, irrigation, and drinking water. However, selecting appropriate technologies to recover valuable resources from POME is challenging, particularly for the purification and upgrading of biogas. Membrane technologies offer an effective approach for transforming POME treatment from an energy-intensive process into a resource recovery system, supporting the decarbonization of palm oil production and advancing global sustainability objectives. This technique is cost-effective and ecofriendly for biogas purification and water reclamation. For biogas purification and upgrading, membrane systems offer the lowest capital and operational costs at 5.654 USD/m³, compared to other technologies, such as 6.249 USD/m³ for water scrubbers and 6.999 USD/m³ for chemical absorbers. This review primarily explores the potential of membranes for gas purification from POME and examines their integration with other processes to develop advanced systems, such as ultrasonicated membrane anaerobic systems and membrane anaerobic systems, to enhance biogas production. In addition, water reclamation from POME is discussed, with ultrafiltration membranes emerging as the most promising candidates. Proton exchange membranes, such as Nafion, are used extensively in microbial fuel cells to improve electricity generation, and this is also summarized. Finally, challenges and future perspectives are highlighted, emphasizing the broader potential of membrane technology in POME wastewater resource recovery. Full article

Aquaponics integrates aquaculture and hydroponics, promoting circularity through the recirculation of water and nutrients. However, waste management remains a challenge. This study aimed to evaluate the anaerobic digestion (AD) of aquaponic effluent (AE) combined with cattle manure (CM) for biogas production. An Indian model biodigester was fed with AE, CM and 1:1, 1:3, and 3:1 W (Water):CM, under anaerobic mono-digestion (MoAD) and 1:1, 1:3, and 3:1 AE:CM under anaerobic co-digestion (CoAD) conditions. The chemical characteristics of the substrates and digestates were assessed, as well as the potential for biogas production over 19 weeks. Overall, CoAD provided better results regarding the chemical characterization of the substrates aimed at biogas production. Notably, the 1:3 AE:CM ratio resulted in the most promising outcomes among the tested conditions. This ratio demonstrated higher efficiency, initiating biogas production by the third week and reaching the highest accumulated volume. It is probable that AE increased the dissolved organic load, optimizing the conversion of organic matter and eliminating the need for additional water in the process. Thus, the CoAD of AE and CM emerged as a promising alternative for waste valorization in aquaponics, contributing to renewable energy generation, agricultural sustainability, and the promotion of the circular economy. Full article

Tannic acid (TA), a prevalent polyphenolic contaminant in industrial effluents, significantly inhibits microbial activity in anaerobic digestion, thereby diminishing wastewater treatment efficiency. In this study, a sulfidized nano zero-valent iron (S-nZVI) composite incorporated into sludge biochar (SB), abbreviated as SB-S-nZVI, was synthesized via a one-step hydrothermal method. The composite’s adsorption capacity for TA and its impact on anaerobic digestion were systematically evaluated. Experimental results showed that SB-S-nZVI achieved a TA removal efficiency of 99.31% under optimal conditions (S/Fe = 0.05, dosage = 0.3 g·L⁻¹), with a maximum adsorption capacity of 337.08 mg·g⁻¹. In anaerobic digestion, the addition of 0.03 g·L⁻¹ SB-S-nZVI enhanced chemical oxygen demand (COD) removal by 3.32%, increased specific methanogenic activity by 62.66%, and improved the microbial community composition, particularly enriching hydrolytic bacteria (Georgenia) and methanogenic archaea (Methanosaeta). The mechanistic analysis revealed that the FeS protective layer of SB-S-nZVI inhibited nano zero-valent iron oxidation and facilitated chemisorption-driven TA removal. This study presents an innovative approach for the integrated treatment of TA-contaminated wastewater by combining adsorption, degradation, and energy recovery. Full article