Effluent Standards Research Articles

Effects of artemia and tilapia density on the ability to treat organic matter in wastewater from white leg shrimps (Litopenaeus vannamei) farming

White leg shrimp (Litopenaeus vannamei) farming effluent contains pollutants that include high levels of total suspended solid (TSS), chemical oxygen demand (COD) and growth promoting substances. This study investigated the possibility of using artemia to filter suspended solids and Tilapia (Oreochromis niloticus) to consume organic waste of shrimp, uneaten food at the bottom of wastewater tanks of industrial shrimp farming. Both artemia and Tilapia had the ability to rapidly reduce organic matter content in wastewater of industrial shrimp farming in tanks. This contributed to reducing total suspended solid in wastewater when discharged into the environment. The biochemical oxygen demand (BOD₅), chemical oxygen demand (COD), total suspended solid (TSS) met effluent standards in Circular No. 44/2010/TT-BNNPTNT and QCVN 11-MT:2015/BTNMT in all of the investigated plots. In the surface wastewater of wastewater tanks, the remaining TSS, BOD₅, and COD contents were the lowest at 6.2 ± 1.1 mg/L, 3.9 ± 0.5 mg/L, and 8.6 ± 1.4 mg/L, respectively, in the stocking density of 300 artemia individuals/L. In the bottom wastewater, the remaining TSS, BOD₅, and COD contents were the lowest at 21.4 ± 5.1 mg/L, 8.5 ± 1.5 mg/L, and 11.6 ± 3.6 mg/L, respectively, in the stocking density of 16 Tilapia individuals/m3.

Effects of Tin Mining on Water Sources in Mwerasandu Tin Mine, Ntungamo District, Uganda

Tin mining is a widespread economic activity across various regions worldwide. Understanding the consequences of such operations is crucial for sustainable water management and environmental conservation. The current study aimed at determining the concentrations tin, lead and mercury in the water sources of Nyakahiimbura Stream in Mwerasandu, and assessed the physico-chemical properties including pH, turbidity, and chemical oxygen demand (COD) of the water from the Nyamuhimbura stream, Ntungamo district. Water samples from three locations, that is; the upstream, impact area and downstream of the Nyakahiimbura water stream were collected during the dry and wet seasons of the year 2024. The samples collected were analyzed for the physico-chemical properties in the laboratory while the Inductively Coupled Plasma-Optical Emission Spectrometry (ICP – OES) was used to determine the concentration of heavy metals in the water samples. The pH, COD values obtained were within the acceptable effluent standards while the turbidity values at the upstream and downstream of the dry season and downstream during the wet season were above the acceptable effluent Standards. The tin concentration was high in the dry season (0.09mg/L) as compared to concentration (0.118mg/L) in the wet season. Lead concentration was the same (0.015mg/L) in both seasons. The concentrations of the heavy metals showed some variations in both dry and wet seasons in the upstream, impacted area and the downstream of the study area as compared to the values of the effluent standards. The study recommends that alternative sources of water for domestic use should be sought of. Also, the government officials especially from the Ministry of Health should carry out awareness campaigns to members of the community about the health risks associated with the uptake of the contaminated waters for domestic purposes. Constructed wetlands should be in place around the mining sites to act as filters for the dangerous metals before the water enters the surrounding environment.

Removal of contaminants in paper dyeing wastewater by Fenton and photo-Fenton processes with biological treatment

Due to the production of huge quantity of potentially toxic and recalcitrant pollutants, which cannot be completely decomposed with conventional biological wastewater treatment processes, in the paper industry, reliable treatment processes are highly required. This study conducted effective experiments of different series of processes to decompose persistent contaminants in the paper wastewater under controlled conditions of the used processes to meet the effluent quality standards of Korea Ministry of Environment in terms of CODMn (< 130 mg/L). For Biological treatment, Fenton, and photo-Fenton processes, various operational parameters were adjusted to determine the optimal conditions for CODMn value. Due to large quantity of refractory contaminants in the wastewater, single treatment process was not enough to meet the requirement of CODMn. Herein, we achieved the goal with two approaches: (1) secondary Fenton oxidation after biological and primary Fenton treatments, and (2) photo-Fenton treatment after biological treatment alone. The secondary Fenton oxidation process is an additional process operated under the same condition of the primary Fenton treatment to treat the effluent from the primary Fenton treatment. Ultimately, the residual CODMn concentrations of the secondary Fenton and single photo-Fenton treatment were 62.7 and 85.3 mg/L, respectively. However, the secondary Fenton required larger amounts of reagents and produced significant amounts of sludge, which require post-treatment, compared to single photo-Fenton treatment. Therefore, it suggests that the application of photo-Fenton was more efficient than the secondary Fenton in terms of economic feasibility and post-treatment requirement.

Removal performance and adsorption behaviour on Mg-based adsorbents in As(III) and F simultaneous removal as in comparison with As(V)

In this study, simultaneous removal tests, with fixed initial arsenic (As) concentration of 1 mg l −1 , for arsenite [As(III)] and fluoride (F) were performed using three types of Mg-based adsorbents. Their As(III) removal performance was of the order of MgCO 3 &lt;&lt; Mg(OH) 2 &lt; MgO. MgO met the environmental standards for As (0.01 mg l −1 ) at initial F concentrations ( C F0 ) of 15 and 30 mg l −1 . MgO and Mg(OH) 2 met the As effluent standard (0.1 mg l −1 ) even at C F0 = 60 mg l −1 . In contrast, MgCO 3 did not meet the effluent standards under the test conditions. The F removal performance of the Mg-based adsorbents followed the order of MgCO 3 &lt; Mg(OH) 2 &lt; MgO. MgO and Mg(OH) 2 met the environmental standard of F (0.8 mg l −1 ), whereas MgCO 3 met the effluent standards for F in non-marine areas (8 mg l −1 ) at C F0 = 15 and 30 mg l −1 , and in marine areas (15 mg l −1 ) even at C F0 = 60 mg l −1 . The As(III) adsorption data fit the Langmuir model for MgO and the Freundlich model for MgO and Mg(OH) 2 , but not MgCO 3 for either model. Notably, the As(III) adsorption behaviour of MgO was strongly influenced by C F0 . Meanwhile, the F adsorption data fit both the Langmuir and Freundlich models for all Mg-based adsorbents.

Treatment of aircraft maintenance wastewater by coupling low-temperature evaporation with Fe–C micro-electrolysis-configured ozonation

ABSTRACT A novel approach combining low-temperature evaporation with Fe–C micro-electrolytic ozone oxidation has been devised for treating substantial volumes of high-concentration organic cleaning wastewater generated during aircraft maintenance activities. The findings from experiments demonstrate impressive average removal rates for various contaminants, including chemical oxygen demand (93.1%), oil concentration (94.0%), suspended solids (98.9%), turbidity (98.8%), chroma (93.8%), total nitrogen (93.7%), and total phosphorus (99.2%). Within this integrated system, the synergistic effects between ozone oxidation, catalytic fillers, and electrochemical processes significantly enhance pollutant removal efficiency. The chemical oxygen demand reduction rates of the cleaning wastewater derived from engine maintenance, mechanical and electrical maintenance, aircraft accessory maintenance, and mixed wastewater exceed 98%. The optimal reaction times for four types of wastewater are 150, 120, 90, and 120 min, respectively. The time can be adjusted according to the different treatment objects in actual operation projects. Moreover, the average concentration efficiency achieved surpasses 92% while meeting all effluent quality standards set forth by municipal sewage networks, and it has reduced the disposal cost of the enterprise by about 80%. This technology provides enterprises with an effective way to reduce energy consumption and expenses.

Field Study and Numerical Modeling to Assess the Impact of On-Site Septic Systems on Groundwater Quality of Jeju Island, South Korea

Septic-derived nitrogen (N) sources have harmful effects on water resources, humans, and ecosystems in several countries. On Jeju Island, South Korea, the rapid increase in personal sewage treatment facilities (PSTFs, also known as on-site septic systems) raises concerns regarding the deterioration of groundwater quality, as groundwater is the sole water resource on the island. Therefore, this study employed a field study and numerical modeling to assess the impact of PSTF effluents on groundwater quality in the Jocheon area of northeastern Jeju. Water quality analysis revealed that the total nitrogen (T-N) concentrations in the effluent exceeded the effluent standards (75–92% PSTFs). The numerical model simulated the transport of N species, showing limited NH4+ and NO2− plume migration near the surface due to nitrification and adsorption. However, NO3− concentrations increased and stabilized over time, leaching on the water table with higher levels in lowland areas and clustered PSTFs. The predictive model estimated a 79% reduction in NO3− leaching when the effluents followed standards, indicating the necessity of effective PSTF management. This study highlights the importance of managing improperly operated septic systems to mitigate groundwater contamination based on an understanding of the behavior of N species in subsurface hydrologic systems.

Decolorization of Textile Dyes by Extracellular Enzymes Produced from Trametes sanguinea and Perenniporia taephropora Immobilized on Natural Media

The color of textile wastewater is still a main problem in wastewater treatment by biological processes. The colored effluents from textile factories usually exceed effluent standards. Therefore, various innovations were developed to treat textile wastewater for decolorization in the effluents. This research aims to decolorize textile wastewater by immobilizing white rot fungi degradation. At first, the 11 fungal stains were tested to find the decolorized efficiency then the high decolorized efficiency fungal stains were immobilized on four material media, namely water hyacinth stalks, coconut husk, corn cob, and loofah. After that, the immobilized fungi were cultivated in the culture media at 30, 60, and 120 C/N ratios, respectively. The results showed that Trametes sanguinea and Perenniporia tephropora were two stains with a high decolorized efficiency of 68.8% and 67.5% respectively, and the decolorized efficiency was increased when immobilized on loofahs and fed with 120 C/N ratio medium. In a comparison of two fungal stains, P. tephropora was found more suitable for the decolorization of textile wastewater than T. sanguinea because T. sanguinea could produce red-orange pigments that induced the colored enhancement in wastewater over time. Finally, immobilized P. tephropora was cultivated in a 120 C/N ratio medium within a 10 L continuous stirred tank reactor (8 L working volume) to investigate the decolorized efficiency, enzymatic activity, and repeated batch. It was found that three repeated cycles were carried out by reusing the immobilized P. tephropora and the highest decolorized efficiency was 63.4%. The enzymatic activity of laccase, manganese peroxidase, and lignin peroxidase was 15.5 U/L, 85.9 U/L, and 0 U/L, respectively

A superstructure-based model for the evolution of park-wide water infrastructure

Industrial parks are crucial to improve material efficiency, economic growth, as well as environmental protection. The increasing demand of freshwater poses a significant challenge for the sustainable development for industrial parks. This work reviews the evolution process of park-wide water infrastructure. A superstructure-based model was used to address the trade-off between water reuse and its impact on the wastewater treatment for the evolutionary state of water infrastructure. In the evolution process of park-wide water infrastructure, five scenarios were defined based on the evolution process of water infrastructure. For wastewater treatment system, centralized or decentralized wastewater treatment plants were deployed according to the evolutionary process of park-wide water infrastructure. The relationship among freshwater consumption, wastewater treatment, and discharge quality were investigated by optimizing the configuration of park-wide water infrastructure. The results indicate that the cost of park-wide water infrastructure with centralized wastewater treatment plant is lower than that with decentralized wastewater treatment plants. Improving the effluent standards for centralized wastewater treatment increases the total cost. For regeneration and reuse, improving the effluent standard for centralized wastewater treatment does not necessarily increase the total cost. The findings indicate that improvement in the discharge standard of centralized wastewater treatment depends on the specifications of the centralized wastewater treatment.

Pilot scale application of a hybrid process based on ozone and BAF process: Performance evaluation for livestock wastewater treatment in a real environment

Environmental pollution was generated continuously because of the slack standard of effluent from livestock wastewater treatment even though the specific treatment process was applied. Despite the continuous ecological pollution caused by livestock wastewater effluent, a comprehensive treatment process for livestock wastewater effluent has not been investigated. This study utilized an ozone-biological aerated filter (BAF) hybrid process at a pilot scale (1st ozone–BAF–2nd ozone), with a 1 m3/day capacity for real-livestock wastewater treatment. Compared with each process configuration, the single-ozone process showed effective performance in removing chromaticity, but the removal ratio of suspended solids, organic matter (OM), and trace-organic compounds (TrOCs) was insufficient, even at high ozone concentrations. The ozone–BAF hybrid process improved the removal ratios of suspended solids and biochemical oxygen demand (BOD) by 61.61 and 17.70 %, respectively, due to aeration and filtration by the BAF; however, TrOC removal ratios remained low, at <75 %. The removal ratios of TrOCs of the 1st ozone–2nd ozone hybrid process were better than those of the ozone–BAF hybrid process (by 28.2–77.9 %) owing to enhanced oxidation from increased ozone exposure to livestock wastewater. Nevertheless, the removal ratios of suspended solids and BOD were below 40 %. Owing to the complementarity between the BAF and 2nd ozone process, the removal ratios of chromaticity, suspended solids, and TrOCs reached 98, 95, and 92 %, respectively, by the optimized 1st ozone–BAF–2nd ozone hybrid process. Our results highlight the necessity of developing a new hybrid process based on ozone and BAF for treating livestock wastewater, and provide guidelines for livestock wastewater treatment.

Novel Cu(200)/Ti cathode for the enhancement of N2 selectivity in direct ammonia electrolysis: The controls of Cu cathode facet orientation

Direct electrochemical ammonia oxidation reaction (AOR) using NiCu-based anodes is effective in removing ammonia from wastewater. However, this type of anode frequently produces undesired byproducts NO3−. Here, we investigated three configurations of novel Cu/Ti cathodes (Cu(111)/Ti, Cu(200)/Ti, Cu(220)/Ti) coupled with Cu/Ni foam (Cu/NF) anode to enhance N2 selectivity (SN2) in a direct ammonia electrolysis cell. Cu(200)/Ti cathode improved SN2 from 35 % (bare Ti cathode) to 60 % and it achieved 10–15 % higher SN2 compared to Cu(111)/Ti and Cu(220)/Ti. The improvement of SN2 on Cu(200) facet was ascribed to the high nitrate electroreduction activity and its conversion to N2. In real wastewater, Cu/NF anode-Cu(200)/Ti cathode paired electrolysis system demonstrated its excellent capability of 88 % NH3 removal with 95 % SN2. Our electrolysis system was capable to maintain the residual NH3-N and the NO3-N below 8 mg L−1, meeting effluent discharge standards. Our findings highlighted the importance of the control of Cu cathode facet orientations for an efficient elimination of NO3– and improvement of N2 production during direct ammonia electrolysis.

Analyzing the variation of greenhouse gas emissions from typical municipal wastewater treatment plants in Beijing during 2007–2021

With the proposal of dual carbon goals and stringent effluent standards, the path of mitigating greenhouse gas (GHG) emissions from wastewater treatment plants (WWTPs) has gained significant research attention. Here, we evaluate the impact of season, elevated standards, operating parameters, and using clean energy on GHG emissions from 8 typical WWTPs in Beijing based on 180 monthly monitoring data. Coupled with the increasing demand for wastewater treatment and 77% more chemical oxygen demand being removed in 2017, total GHG emissions from 5 WWTPs increased by 89% compared to the status quo in 2007, and after energy structure reform total GHG emissions decreased by 17% in 2021. Scenario analysis reveals that energy recovery and clean energy utilization provide 64% and 48% mitigation potential by 2050, respectively. We argue stricter effluent standard leads to GHG emissions growth in WWTPs; meanwhile, process optimization, proper temperature and targeted policies at WWTPs can reduce GHG emissions.

Accurate prediction and intelligent control of COD and other parameters removal from pharmaceutical wastewater using electrocoagulation coupled with catalytic ozonation process.

In this study, we employed the response surface method (RSM) and the long short-term memory (LSTM) model to optimize operational parameters and predict chemical oxygen demand (COD) removal in the electrocoagulation-catalytic ozonation process (ECOP) for pharmaceutical wastewater treatment. Through RSM simulation, we quantified the effects of reaction time, ozone dose, current density, and catalyst packed rate on COD removal. Then, the optimal conditions for achieving a COD removal efficiency exceeding 50% were identified. After evaluating ECOP performance under optimized conditions, LSTM predicted COD removal (56.4%), close to real results (54.6%) with a 0.2% error. LSTM outperformed RSM in predictive capacity for COD removal. In response to the initial COD concentration and effluent discharge standards, intelligent adjustment of operating parameters becomes feasible, facilitating precise control of the ECOP performance based on this LSTM model. This intelligent control strategy holds promise for enhancing the efficiency of ECOP in real pharmaceutical wastewater treatment scenarios. PRACTITIONER POINTS: This study utilized the response surface method (RSM) and the long short-term memory (LSTM) model for pharmaceutical wastewater treatment optimization. LSTM predicted COD removal (56.4%) closely matched experimental results (54.6%), with a minimal error of 0.2%. LSTM demonstrated superior predictive capacity, enabling intelligent parameter adjustments for enhanced process control. Intelligent control strategy based on LSTM holds promise for improving electrocoagulation-catalytic ozonation process efficiency in pharmaceutical wastewater treatment.

Distinct comammox Nitrospira in high-rate down-flow hanging sponge reactor treating municipal wastewater

A down-flow hanging sponge (DHS) reactor is a trickling filter system used for wastewater treatment, which employs sponges to retain biomass. This study assessed the process performance of a compact DHS combined with a sedimentation tank with seven phases at varying hydraulic retention times (HRT) over 500 days. The BOD of the DHS effluent was maintained at 4.0 ± 0.5 mg·L-1 for the shortest HRT 0.3 ± 0.1 h. The nitrification efficiency was considerably impacted by the reduced HRT, with NH4+-N and NO3–-N concentrations of 9.0 ± 1.2 mgN·L-1 and 2.2 ± 0.5 mgN·L-1, respectively. Nevertheless, the effluent complied with effluent discharge standards throughout the trial period. The number of comammox 16S rRNA gene copies ranged from 5.58 to 13.2 × 107 copies·mL−1, indicating that sponges biomass retained carrier can provide favorable conditions for comammox growth and could contribute to nitrification in the high-rate DHS reactor.

A strategic approach to sustainable wastewater management and reuse in Saudi Arabia

The Kingdom of Saudi Arabia (KSA) faces challenges in protecting its limited natural water resources. The centralized sewage treatment plants (STPs) contribute to conserving natural water resources in various regions of KSA. For sustainable wastewater management strategies in arid environments, the performance of STPs needs to be assessed for various beneficial uses in addition to the existing regulations. The present study used extensive effluent quality data of four STPs to develop a performance assessment approach using multi-criteria and principal component analyses. The performance levels were derived from the compliance rate of effluent standards with different reuses and the efficacy of biosolids management. The proposed approach evaluated the STPs based on the planned applications of treated effluents, considering the land use characteristics of each plant’s disposal point. The factors loadings obtained for the STPs, encompassing total suspended and dissolved solids, and total dissolved solids, oxidizing demanding pollutants (BOD and COD), and nutrients (NO3 and PO4), with 3 to 4 principal components demonstrating above 60% of the effluent monitoring data, established the importance of the effluent quality parameters. The effluent quality index (EQI) was developed for existing and potential reuses, e.g., irrigation, landscaping, fishery, and recreation, during dry (summer) and wet (winter) periods. All STPs showed high EQI for both periods for the present reuse standards of unrestricted irrigation and landscaping. The overall performance index, aggregating EQI and the efficacy of sludge management practices, illustrated declining performance, suggesting staged improvements (tertiary-level treatment, air floatation, sludge digestion, and waste-to-energy) through a periodic assessment process. STPs must enhance their sludge management efficacy to produce Class-A biosolids and waste-to-energy. The proposed approach will help make strategic decisions regarding improvements for STPs and the allocation of financial resources to protect natural resources in various regions across KSA.

Horizontal-flow constructed wetlands by phytoremediation using vetiver grass, common reed, and canna lily as tertiary wastewater treatment for the reduction of pollutant concentrations of ammonia, phosphates, and nitrates

Abstract The discharge of untreated wastewater into rivers and water bodies poses significant environmental and public health risks. High concentrations of contaminants like heavy metals and pharmaceuticals disrupt rivers, exacerbating waterborne diseases, and leading to unsafe water in the Philippines. This study proposed the use of horizontal-flow constructed wetlands as a tertiary treatment method utilizing the plants: vetiver grass, common reed, and canna lily, to reduce pollutant concentrations in wastewater. This is to ensure compliance with water quality guidelines and general effluent standards under the Class SB Category, water suitable for fishery, tourist zones, and recreational activities. The research investigated the efficiency of phytoremediation beds in removing pollutants from wastewater under fixed hydraulic retention times. The efficiency of reducing pollutants and adsorption isotherms (Freundlich and Langmuir) were calculated to analyze the results of the sampling. Phytoremediation bed 1 demonstra ted efficient ammonia removal by 64.64%. Phytoremediation bed 2 was proficient in reducing nitrates at 83.85%, while phytoremediation bed 3 effectively reduced phosphate to an average of 26.26%, achieved after a 6-hour retention time. In addition, Freundlich adsorption isotherm was observable in most parameters in phytoremediation bed 1 such as ammonia as nitrogen, TDS, COD, and DO. Phytoremediation bed 3 exhibited the same adsorption isotherm on ammonia as nitrogen. Conclusively, the phytoremediation system met the Department of Environment and Natural Resources - Updated Water Quality Guidelines and General Effluent Standard (GES) for all parameters tested.

Planning Evaluation of Wastewater Treatment System of Jakarta Islamic Hospital Sukapura Kelapa Gading

This study aims to evaluate the effectiveness of the Wastewater Treatment Plant (WWTP) at the Jakarta Islamic Hospital Sukapura Kelapa Gading in meeting government regulations and effluent quality standards. Using evaluation and observation methods, primary and secondary data were collected to analyze the condition of the WWTP, including wastewater quality based on regulated parameters. The results showed that although the WWTP utilizes an anaerobic-aerobic biofilter system, there are still problems in maintenance and inadequate containment capacity. This resulted in the inability of the WWTP to meet quality standards for parameters such as Total Coliform and E.coli. Recommendations for improvement include increasing storage capacity, improving equipment, and increasing maintenance frequency.

Water-Energy Nexus Flow Analysis of a Wastewater Treatment Plant in Thailand

Abstract The Wastewater Treatment Plant in Thailand plays a vital role in treating raw domestic wastewater. As the demand for treating wastewater grows, the energy requirements associated with treatment processes become essential. This study aims to identify energy-intensive areas in wastewater treatment plants and provide inventory data for the indirect environmental impact. It also determines the suitable opportunities to recover energy from wastewater treatment plants. The water-energy nexus was examined through Material Flow Analysis (MFA) using Substance Flow Analysis (STAN) Software. The wastewater treatment plant is extended to produce water for reuse. System allocation is adopted to separate the treated wastewater and reuse water products. In Thailand, the aeration tank unit is the most energy-intensive. This condition can be explained by operating the aeration tank, which accounts for 33.87% of the total energy demand. The research found that around 0.155 kWh/m3 is needed for treating raw domestic wastewater to meet the effluent standard. The extended treatment for converting the raw wastewater into reuse water requires 0.3286 kWh/m3. Reuse water is beneficial for providing sustainable water resources but requires a 112% energy increase. The plant relies on Thailand’s EGAT Energy Mix (58.09% Natural Gas, 29.01% Lignite, 10.21% Hydropower, 2.52% Diesel, 0.16% Fuel Oil, 0.002% Geothermal Energy and 0.008% remain unidentified). Rather than fully relying on Thailand EGAT, the research suggests renewable energy installations and nutrient recovery options. Solar panels and micro-hydro power generation are promising ideas to install. Moreover, recovering the nutrients from wastewater can address environmental problems and offer valuable resources simultaneously. The findings of this Study provide profound benefits for developing sustainability in wastewater treatment plants.

Analyzing greenhouse gas emissions and influencing factors of 247 actual wastewater treatment plants in China using emission factor and operational data integrated methods (ODIM).

In response to China's policies on pollution control and carbon emission (CE) reductions, more stringent regulations have been implemented to evaluate CE in wastewater treatment facilities. In this study, we have analyzed CE from China's wastewater treatment plants (WWTPs) and influencing factor. Emission factor (EF) and operational data integrated methods (ODIM) were utilized to measure emissions, using data collected from 247 WWTPs over a 1-year period across seven regions in China. The average CE intensity was 0.45 kgCO2-eq/m3, affected by region, season, influent water quality, treatment processes, effluent discharge standards, and facilities. The scale effect was obvious only in the range of 2 × 105 m3/day. Underground WWTPs exhibited significantly higher CE compared to aboveground WWTPs. In summary, the assessment of CE in 247 actual WWTPs not only identifies emission reduction potential but also provides a scientific basis for formulating targeted emission reduction measures.

Nutrient Removal and Recovery from Municipal Wastewater

With the ongoing amendment of the EU legislation on the treatment of urban wastewater, stricter requirements for the removal of pollutants are expected, which calls for the need for innovative wastewater treatment technologies. Biological systems are still the first choice. A survey of typical bioreactors applied in wastewater treatment is presented. The wastewater treatment objective, biochemical environment, and microbial growth are selected as the main criteria for the classification of these bioreactors. Hydraulic and kinetic aspects are considered, along with the advantages and drawbacks of these bioreactors regarding the selection of the appropriate type of reactor; as well, details regarding the operation of reactors are mentioned. The aim of this paper is to provide operators and designers with a brief overview of the selected traditional and advanced processes, reactors, and technologies for nutrient removal from municipal wastewater. The possibilities and limitations in complying with more strict effluent standards are also discussed. Methods of nutrient recovery are added value. From the evaluation of the published papers, we determine that the currently applied traditional methods for nutrient removal have the potential to also convey the expected stricter limits.

Fe(II)-driven spatiotemporal assembly of heterotrophic and anammox bacteria enhances simultaneous nitrogen and phosphorus removal for low-strength municipal wastewater

The mainstream anaerobic ammonium oxidation (anammox) faces considerable challenges with low-strength municipal wastewater. A Fe(Ⅱ)-amended partial denitrification coupled anammox (PD/A) process was conducted and achieved a long-term and efficient nitrogen and phosphorus removal, yielding effluent total nitrogen and phosphorus concentrations of 1.97 ± 1.03 mg/L and 0.23 ± 0.13 mg/L, respectively, which could well meet more stringent effluent discharge standard of some wastewater treatment plants in specific geographical locations, e.g., estuaries. Fe(Ⅱ)-driven vivianite formation provided key nucleuses for the optimization of the spatial distribution of heterotrophic and anammox bacteria with enhanced extracellular polymeric substances as key driving forces. Metagenomics analysis further revealed the increase of key genes, enhancing anammox bacteria homeostasis, which also bolstered the resistance to environmental perturbations. This study provided a comprehensive sight into the function of Fe(Ⅱ) in mainstream PD/A process, and explored a promising alternative for synergetic nitrogen and phosphorus removal for low-strength municipal wastewater treatment.