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To prevent water scarcity, wastewater must be discharged to the surface or groundwater after being treated. Another method is to reuse wastewater in some areas after treatment and evaluate it as much as possible. In this study, it is aimed to recover and reuse the caustic (sodium hydroxide, NaOH) used in the recycling of plastic bottles from polyethylene terephthalate (PET) washing wastewater. Chemical substances used in the industry will be significantly reduced with chemical recovery from wastewater. Ultrafiltration (UP150) and nanofiltration (NP010 and NP030) membranes were used for this purpose in our study. Before using nanofiltration membranes, pre-treatment was performed with coagulation-flocculation process to reduce the pollutant accumulation on the membranes. Different coagulants and flocculants were used to find suitable coagulants and flocculants in pre-treatment. The pre-treated wastewater using aluminum oxide, which supplied the highest chemical oxygen demand (COD) removal (76.0%), was used in a dead-end filtration system to be filtered through NP010 and NP030 membranes at different pressures (10–30 bar). In the same filtration system, raw wastewater was filtered through a UP150 membrane. Among these treatment scenarios, the best method that could remove pollutants and provide NaOH recovery was selected. After each treatment, pH, conductivity, COD, and NaOH analyses were performed. The maximum NaOH recovery (98.6%) was obtained with the UP150 membrane at 5 bar.

The energy self-sufficiency of wastewater treatment plants has become an essential aspect of sustainable water and energy resource management. On the other hand, due to the expansion of urban conglomerations and agricultural activities, as well as more frequent and erratic meteorological phenomena (e.g., droughts), the majority of EU nations are confronted with water scarcity and the deterioration of water quality. As a consequence, EU member states pledged to implement “tertiary treatment” in all municipal wastewater treatment facilities by the end of 2040. This publication presents an analysis of the efficiency of an energy-efficient gravity cloth disk filter used for treating municipal wastewater in a treatment plant located in a tourist resort in Poland, operating under variable hydraulic loading conditions. Gravity cloth disk filters appear to be the least energy-consuming. The energy consumption of disk filters was 13 Wh/m3 in 2024. The filter ensures the leveling of disturbances in the operation of earlier treatment stages, particularly in terms of retaining total suspended solids (TSSs). The achieved efficiency of TSS removal was 45%. The TSS value in the outflow from the filter did not exceed the limit value from the permit (35 mg/L). When operated correctly, additional filtration and disinfection may become essential components of a wastewater treatment plant, enabling the achievement of wastewater quality that supports water recovery for technological and agricultural purposes, particularly in small, non-industrial areas. They should also consume less energy than other advanced technologies used in the third and fourth stages of wastewater treatment.

Recovery of phosphorus (P) from wastewater is a topic of great interest. Besides being a non-renewable resource, P discharge in receiving waters can trigger algae blooms. The present study aimed to quantify the removal of P from two sites at a wastewater treatment plant using calcined eggshell (CES) as adsorbent. CES was prepared from raw shells calcined at 600 °C (CES600) and 800 °C (CES800). CES at 800 °C proved to be an efficient material for P removal. Efficiencies greater than 70% were achieved using CES800 concentrations of 0.1 g L−1 for synthetic sample, 0.3 g L−1 for preliminary treated wastewater and 20 g L−1 for supernatant from sludge anaerobic digester. The adsorption process was fast, occurring mostly in the first 30 min. Both Langmuir and Freundlich isotherms fitted the experimental data on adsorption. In kinetic experiments, a pseudo-second-order model fitted P adsorption from synthetic, preliminary effluent and digester supernatant. Thermogravimetric analysis showed a 54% eggshell mass loss at 800 °C. Calcination increased calcium and reduced carbon fractions in the eggshells, while increasing the surface area.

This study investigates the application of electrocoagulation for enhancing the biodegradability of organic matter in automobile service station wastewater, notorious for its contamination with polyaromatic hydrocarbons, heavy metals, and surfactants. Optimization of key variables such as electrode material, current density, and electrical consumption is conducted, with correlation analysis assessing their impact on water quality. Experimental setups utilize a vertical configuration comprising eight monopolar steel electrode plates as cathodes and eight counter electrodes (either iron or aluminum) connected in parallel. Results indicate that employing iron as the sacrificial electrode significantly increases the biochemical oxygen demand/chemical oxygen demand (BOD/COD) ratio, highlighting the efficacy of heightened power levels in enhancing organic matter degradation. Optimal removal efficiencies, including 87.5 for COD, 96.01 for BOD, and 92.2% for total solids, are achieved at a current density of 42 A/m2 and energy consumption of 360 kWh/m3, while maintaining pH levels between 6 and 9. The findings underscore the potential of electrocoagulation with Fe, Al as anodes, and stainless-steel cathodes as an efficient wastewater treatment approach, particularly for COD, BOD, and solid particle removal, thus contributing significantly to environmental sustainability.

Treatment of industrial wastewater by electrocoagulation (EC) is one of the most efficient methods to remove pollutants. Paper-recycling wastewater is a complex mixture containing toxic and recalcitrant substances, indicating complexity and difficulty of its treatment. The aim of the present study was to assess the effectiveness of paper-recycling wastewater treatment by EC process using aluminum (Al) and iron (Fe) plate electrodes. Removal of chemical oxygen demand (COD), total suspended solids (TSS), color and ammonia from paper-recycling mill effluent was evaluated at various electrolysis times (10–60 min), voltage (4–13 V) and pH (3.5–11). The optimum process conditions for the maximum removal of COD, TSS, color and ammonia from paper-recycling industry wastewater have been found to be pH value of 7, treatment time of 60 min and voltage of 10 V. Under optimum operating conditions, the removal capacities of COD, TSS, color and ammonia were 79.5%, 83.4%, 98.5% and 85.3%, respectively. It can be concluded that EC could be considered as an effective alternative for treatment of paper-recycling wastewater.

Bioelectrochemical anaerobic ammonium oxidation (anammox) systems allow eco-friendly removal of nitrogen from reject wastewater coming from biogas processing as the anammox bacteria have previously shown to have c-type cytochromes acting in the extracellular electron transport (EET) mechanism between the bacteria and electrode. The anammoxosome compartment present in anammox bacteria features a highly curved membrane and contains tubular structures along with electron-dense particles that contain iron, which could enhance the process of EET and enhance nitrogen removal by properly applied potentials. In this study, nitrogen removal was investigated in the electrostimulated anammox nitrogen removal (EANR) cells operated comparatively at open circuit and at applied potentials of − 300 mV, − 500 mV, and − 700 mV vs. Ag/AgCl. At peak performance (at − 700 mV vs. Ag/AgCl), the EANR showed up to 140% higher specific nitrogen removal rate (11.2 ± 0.3 g N/m 2 /day) compared to the control reactors without applied potential (8.3 ± 0.2 g N/m 2 /day). The microbial community on the cathode with the applied potential had a higher relative proportion of unclassified Candidatus Brocadia (7.5%) compared to inoculum (> 0.01%), in contrast to cathode without potential (0.74%) and control (0.2%). The EANR system demonstrated to achieve ammonium and nitrite removal efficiencies of 91% and 53%, respectively, during a 24-h test cycle from an initial TN concentration of ~ 100 mg N/L. After 150 h, it achieved complete removal of all nitrogen compounds, reaching a 100% removal efficiency. The EANR would be very useful in the establishment of field-scale bilateral anammox-bioelectrochemical technology combining microbial fuel cell bioanodes and EANR biocathodes for wastewater treatment.

Increased interest in sustainable agriculture and bio-based industries requires that we find more energy-efficient methods for treating cellulose-containing wastewaters. We examined the effectiveness of simultaneous electricity production and treatment of a paper recycling plant wastewater using microbial fuel cells. Treatment efficiency was limited by wastewater conductivity. When a 50 mM phosphate buffer solution (PBS, 5.9 mS/cm) was added to the wastewater, power densities reached 501 ± 20 mW/m², with a coulombic efficiency of 16 ± 2%. There was efficient removal of soluble organic matter, with 73 ± 1% removed based on soluble chemical oxygen demand (SCOD) and only slightly greater total removal (76 ± 4%) based on total COD (TCOD) over a 500-h batch cycle. Cellulose was nearly completely removed (96 ± 1%) during treatment. Further increasing the conductivity (100 mM PBS) increased power to 672 ± 27 mW/m². In contrast, only 144 ± 7 mW/m² was produced using an unamended wastewater (0.8 mS/cm) with TCOD, SCOD, and cellulose removals of 29 ± 1%, 51 ± 2%, and 16 ± 1% (350-h batch cycle). These results demonstrate limitations to treatment efficiencies with actual wastewaters caused by solution conductivity compared to laboratory experiments under more optimal conditions.

The development of efficient and sustainable water recycling systems is essential for long-term human missions and the establishment of space habitats on the Moon, Mars, and beyond. Humidity condensate (HC) is a low-strength wastewater that is currently recycled on the International Space Station (ISS). The main contaminants in HC are primarily low-molecular-weight organics and ammonia. This has caused operational issues due to microbial growth in the Water Process Assembly (WPA) storage tank as well as failure of downstream systems. In addition, treatment of this wastewater primarily uses adsorptive and exchange media, which must be continually resupplied and represent a significant life-cycle cost. This study demonstrates the integration of a membrane-aerated biological reactor (MABR) for pretreatment and storage of HC, followed by brackish water reverse osmosis (BWRO). Two system configurations were tested: (1) periodic MABR fluid was sent to batch RO operating at 90% water recovery with the RO concentrate sent to a separate waste tank; and (2) periodic MABR fluid was sent to batch RO operating at 90% recovery with the RO concentrate returned to the MABR (accumulating salinity in the MABR). With an external recycle tank (configuration 2), the system produced 2160 L (i.e., 1080 crew-days) of near potable water (dissolved organic carbon (DOC) < 10 mg/L, total nitrogen (TN) < 12 mg/L, total dissolved solids (TDS) < 30 mg/L) with a single membrane (weight of 260 g). When the MABR was used as the RO recycle tank (configuration 1), 1100 L of permeate could be produced on a single membrane; RO permeate quality was slightly better but generally similar to the first configuration even though no brine was wasted during the run. The results suggest that this hybrid system has the potential to significantly enhance the self-sufficiency of space habitats, supporting sustainable extraterrestrial human habitation, as well as reducing current operational problems on the ISS. These systems may also apply to extreme locations such as remote/isolated terrestrial locations, especially in arid and semi-arid regions.

This paper reports the effects of changing pH (5-7) and temperature (T, 40-60 °C) on the efficiencies of bacterial hydrolysis of suspended organic matter (SOM) in wastewater from food waste recycling (FWR) and the changes in the bacterial community responsible for this hydrolysis. Maximum hydrolysis efficiency (i.e., 50.5% reduction of volatile suspended solids) was predicted to occur at pH 5.7 and T = 44.5 °C. Changes in short-chain volatile organic acid profiles and in acidogenic bacterial communities were investigated under these conditions. Propionic and butyric acids concentrations increased rapidly during the first 2 days of incubation. Several band sequences consistent with Clostridium spp. were detected using denaturing gel gradient electrophoresis. Clostridium thermopalmarium and Clostridium novyi seemed to contribute to butyric acid production during the first 1.5 days of acidification of FWR wastewater, and C. thermopalmarium was a major butyric acid producer afterward. C. novyi was an important propionic acid producer. These two species appear to be important contributors to hydrolysis of SOM in the wastewater. Other acidogenic anaerobes, Aeromonas sharmana, Bacillus coagulans, and Pseudomonas plecoglossicida, were also indentified.

To address global concerns such as population expansion, urbanization, and industrialization, which are contributing to increased water pollution and shortages, sustainable water management relies on wastewater reuse. The purpose of this review is to investigate the significant role that hybrid catalytic materials and nanocatalysts play in the process of improving wastewater treatment technologies. By employing these materials and other advanced oxidation techniques, nanocatalysts are evaluated to assess their effectiveness in eliminating heavy metals and degrading persistent organic contaminants. The bibliometric assessment of research trends from 2015 to 2024 reveals a growing emphasis on the applications of nanotechnology in wastewater treatment. Within the scope of this review, the internal and extrinsic parameters that influence catalytic performance are investigated. These factors include particle size, light intensity, catalyst loading, and ambient pH conditions. Nanocatalysts hold great promise; however, several lingering concerns need to be addressed. These issues include high synthesis costs, scalability challenges, and environmental toxicity. These issues underscore the need to develop sustainable synthesis procedures, improved recovery mechanisms, and policy frameworks. Recent achievements in this sector include synthesizing nanomaterials that are safe for the environment, developing hybrid catalytic systems, and integrating these systems into existing treatment infrastructures to enhance efficiency and cost-effectiveness. The resolution of these issues will contribute to the establishment of nanocatalysts as transformative tools and green materials for wastewater treatment, for promoting the sustainability of water on a global scale and protecting the environment. The application of these hybrid materials for wastewater treatment is a topic of significant interest in environmental research.