Decentralized Wastewater Treatment Systems Research Articles

Moving Bed Biofilm Reactor (MBBR) for Decentralized Grey Water Treatment: Technical, Ecological and Cost Efficiency Comparison for Domestic Applications

The reuse of greywater has several advantages, including reduced freshwater extraction from rivers, aquifers, and groundwater; reduced need for desalination; less environmental impact from septic tanks and water treatment plants; decreased energy consumption; and reduced chemical pollution. The main objectives of this review study are to assess the technical attributes, ecological impacts, and cost-efficiency of Moving Bed Biofilm Reactor (MBBR) water treatment technology compared to similar available technology for small to medium-sized, decentralized applications in residential and commercial settings such as home gardening, sanitation, and landfills. Previous studies indicate that hybrid technologies such as MBBR are the most promising methods for the total removal of contaminants in wastewater in a decentralized setting. However, the initial capital cost of this technology for small and medium-scale domestic applications worldwide is high and so is a limiting factor in the expansion of its utilization. Expansion of domestic use of such Decentralized Wastewater Treatment Systems (DWTS) could increase the economies of scale and therefore reduce the initial capital costs for this useful water treatment. For the MBBR system, Chemical Oxygen Demand (COD) removal efficiency was found to be 70%, Total Suspended Solids (TSS) removal was found to be 97%, and turbidity removal was 98%

A review on decentralized wastewater treatment systems in India

Pollution of water resources and a lack of potable water are two important issues that city dwellers in India encounter. The passage of untreated sewage down municipal drains is one of the most significant sources of water resource pollution. In densely populated areas, effective sanitation and wastewater management is becoming increasingly difficult. In many developing nations, centralized sewage and wastewater treatment facilities serve only a section of big cities, and on-site sanitation is frequently insufficient in heavily populated areas. There is a demand for complementary and intermediate solutions. DEWATS (community-managed anaerobic decentralized wastewater treatment systems) is a good option for the possibility of relatively fast sanitation improvements in high-priority neighbourhoods where the local authority is not providing a full sanitation service. The following technical treatment modules are typically seen in DEWATS. The primary treatment consists of sedimentation ponds, settlers, septic tanks or bio digester, secondary treatment consists of anaerobic baffled reactors, anaerobic filters or anaerobic and facultative pond systems, secondary aerobic/facultative treatment consists of horizontal gravel filters and post-treatment consists of aerobic polishing ponds. The experience of India in establishing community-managed DEWATS on a large scale is examined in this review.

Sustained Phosphorus Removal by Calcareous Materials in Long-Term (Two Years) Column Experiment

(1) Phosphorus (P) removal has proven difficult in decentralized wastewater treatment systems, and external filters installed with a highly P sorbent material have been proposed to improve the P removal. In particular, calcium (Ca) rich materials have shown promising results. (2) Eight materials (five calcareous materials, one quartz sand, and two Sol–Gel coated calcareous materials) were tested in columns fed with P-spiked tap water for two years. The experiment was operated under four periods with increased P concentration from 3.3 to 21.5 mg P L−1, and with increased surface loading rate from 18 to 227 mm d−1. After termination, the element content was measured in four column height fractions. (3) Initially, all columns removed P effectively and the calcareous materials (CAT, CAT A, and CAT C) maintained an effective removal until termination, while increases in effluent P concentration were detected already after 7 weeks for SAN and after 80–90 weeks for OPO, PHO, CAL, and HYG. The highest P content for materials were measured for the bottom fraction closest to the inlet distribution. For most materials, we observed a good agreement between the maximum sorption capacity (Qmax) and the P content in the bottom fraction; however, a discrepancy was observed for CAL, CAT A, and CAT C. (4) In conclusion, the calcareous materials provided a consistent P removal for all 24 months. Additionally, the Sol–Gel coating had a minimal effect on the P removal capacity contrary to previous findings in batch experiments for the coated materials.

Greening Urban Areas with Decentralized Wastewater Treatment and Reuse: A Case Study of Ecoparque in Tijuana, Mexico

In rapidly growing urban areas, such as Tijuana, Mexico, the presence of urban green spaces (UGSs) can help stem soil erosion, improve infiltration, slow runoff, decrease flooding, reduce air pollution, and mitigate climate change. In many water-scarce parts of the world, where centralized wastewater treatment is not accessible or practical, decentralized wastewater treatment systems (DEWATSs) have the potential to supply the water needed for irrigating UGSs. Here, we first review UGS systems supported by DEWATSs and the water quality guidelines and challenges associated with implementing DEWATSs for urban greening in different countries, including Mexico. We also critically examine the linkages between the lack of UGSs in Tijuana, Mexico, extensive soil erosion, and failing sanitation infrastructure that has led to the infamously poor water quality in the Tijuana River. Tijuana’s Ecoparque Wastewater Treatment Facility, a low-energy, aerobic DEWATS, which collects, treats, and discharges residential sewage for localized landscape irrigation, demonstrates how DEWATSs can meet the water demands for urban greening in rapidly urbanizing cities. The aerobic decentralized treatment using a gravity-fed trickling biofilter resulted in a >85% removal of chemical oxygen demand and dissolved organic carbon. Prior to treatment facility upgrades, there was a ~2 log reduction in total coliform and Escherichia coli and a <20% decrease in ammonia from the influent to final effluent. After the addition of a maturation pond in 2020, the effluent met Mexico standards for irrigation reuse, with a ~4 log reduction in fecal coliforms from the influent to final effluent. Case study results demonstrated the potential for decentralized wastewater treatment to meet effluent standards for landscape irrigation, provide water for urban greening, and prevent pollution in the Tijuana River and other urban waterways.

Correction: Gallagher, J.; Gill, L.W. The Life Cycle Environmental Performance of On-Site or Decentralised Wastewater Treatment Systems for Domestic Homes. Water 2021, 13, 2542

In the original publication [...]

Efficacy Assessment of Decentralized Wastewater Treatment Systems in treating Faecal Sludge within Dar es Salaam City

Dar es Salaam Water and Sewerage Authority (DAWASA) considers DEWATS as effective system for faecal sludge management especially from unplanned settlements. No study has been done in Tanzania to assess the treatment efficiency, adoptability and sustainability of the systems. That being the case, this study aimed at assessing the treatment efficiency of the Decentralized Treatment Systems installed within the city. Kigamboni and Mburahati DEWATS were selected as case study areas for the study whereby, quantitative method was used for data collection. The collected results showed that most of the physical parameters were within the allowable range specified by Tanzanian Standards for municipal wastewater discharge (TZS 860:2006). Nitrate and Phosphate levels were within the allowable range at both treatment plants. The BOD5 and COD for Kigamboni DEWATS were four times higher than the maximum allowable safe limit for each. Both Kigamboni and Mburahati DEWATS failed to lower the coliform levels of faecal sludge to meet the maximum allowable discharge standard (10,000 cfu/100 ml) by having the effluent quality of 115,000 cfu/ 100 ml and 22,875,000 cfu/100 ml respectively. Addition of dosing chamber between the gravel filter and polishing dosed at 6mg/l of chlorine remediated the state.

The Effect of Sol-Gel Coatings on the Phosphorus (P) Adsorption Capacity of Calcareous Materials for Use in Water Treatment

(1) Phosphorus (P) removal has proven difficult in decentralized wastewater treatment systems, and P binding material, installed as an external filter, has been proposed for improving P removal. Especially, calcium (Ca)-rich materials have shown promising results. (2) Five calcareous materials were tested with isotherm batch experiments. The material with the highest P adsorption capacity was selected to undergo different Sol-Gel coatings, i.e., different coating dilution ratios (1:10, 1:5, and 1:1) and exposure periods (5, 10, and 15 min). The seven coated materials were evaluated by isotherm experiments. (3) The maximum adsorption capacity (Qmax) was determined by fitting the Langmuir equation. Qmax for the non-coated materials, and ranged from 0.7 (sand) to 35.1 (Catsan) mg P g−1 DW, while the coated materials ranged from 7.8 to 24.7 mg P g−1 DW depending on the coating. Based on the rotated Principal Component Analysis, the most important parameters for Qmax were the texture and the Ca content. (4) Catsan was the most promising material, but when performing a Sol-Gel coating, a trade-off between preserving Qmax and the coating thickness were evident, as the materials with the thinner coating preserved more of the sorption capacity. The development of P binding materials constitutes a useful technology in decentralized wastewater treatment systems.

A novel approach to baseline water quality assessment at local and catchment scale: a case study from Berambadi, India.

Optimal design and maintenance are necessary for the sustainability of wastewater treatment systems. In this study, we present the outcome of a novel approach to baseline assessment conducted prior to the design and deployment of a decentralized wastewater treatment system at a school in rural India. The baseline water quality monitoring protocol was deployed to assess (a) the quality and quantity of wastewater (greywater and blackwater) flows from the school and (b) the status of surface water and groundwater quality in the catchment. Hourly greywater flows and water quality trends were monitored across four seasons at the school. Average freshwater consumption at the school was 518 ± 322 L/day for hand washing and 287 ± 97 L/day for cooking meals. Greywater generation showed high hourly variations in COD levels. Greywater generated from hand wash and kitchen sources contributed to 110g/day and 96g/day of BOD5 respectively and 214g/day and 141g/day of COD respectively. Based on additional data from a self-reporting sanitation survey, the organic contaminant load generated from the toilet was estimated to be 1.5 ± 0.1kg COD/day. At the catchment scale, both groundwater and surface water quality were monitored seasonally to assess the impact of raw sewage and stormwater inputs. Compared with borewells, high nitrate-N levels (> 10mg/L) were observed in the village hand pump samples throughout the year. Maximum nitrate-N (16mg/L) and fecal coliforms (3.9 log MPN/100mL) levels were observed in surface waters during monsoons, indicating the impact of sewage and surface runoff on water quality. The proposed approach is useful to estimate data on freshwater use and wastewater generation at the school and hence to make the case for, and design of, a sustainable water management intervention.

Systematic review of the last 20 years of research on decentralized domestic wastewater treatment in Brazil: state of the art and potentials.

A DEWATS (decentralized wastewater treatment system) is an alternative for expanding sanitation. In Brazil, DEWATS is acknowledged by law and is part of the National Sanitation Plan strategy for achieving the treatment of 85.6% of all the generated wastewater by 2033, improving the current treatment index of 49%. This review's aim is to identify DEWATS studies in Brazil and to verify their potential for narrowing the national wastewater treatment deficit. Hence, aspects such as cost, maintenance, and efficiency were assessed. The archival research method (ARM) was used to identify papers published in the last 20 years through the scientific databases of Scopus, Science Direct, and Web of Science. Data regarding the general characteristics of each study were collected and compared to Brazilian environmental regulation and sanitation status. The results showed the evaluation of different technologies such as DEWATS, highlighting their flexibility and potential use in 79% of Brazilian counties. However, although 81% of the studies conducted performance analysis, none covered the main parameters required by Brazilian law. Although legal gaps for DEWATS improvement and consolidation have been identified and the interest in studying DEWATS has been increasing in the last five years, many barriers to their widespread use remain.

Field-scale decentralized domestic wastewater treatment system: Effect of dynamic loading conditions on the removal of organic carbon and nitrogen

The field–scale decentralized wastewater treatment system (DWTS) was developed with an anaerobic baffled reactor (ABR) and a newly configured hybrid constructed wetland (HCW) vegetated with Typha angustifolia and Canna indica to treat 42 kLd of domestic wastewater. Biorack baffled constructed wetland (BBCW) and baffled vertical flow constructed wetland (BVFCW) were used in the first and second stage of HCW respectively. DWTS was assessed for its efficiency to remove COD, BOD and TKN under high (varying flow and varying COD) and moderate (constant flow and varying COD) dynamic loading conditions. The tracer study and pertinent computation showed the good performance of DWTS in its hydraulic efficiency. COD of raw wastewater was the treatment-limiting step in ABR. BBCW sustained larger fluctuations in loading rates [hydraulic (0.43–10.29 m3/m2.d) and organic (0.08–2.30 kgCOD/m2.d)]. The draining (unsaturated) conditions enhanced COD and BOD removal in BVFCW. DWTS was found to be efficient for the average removal of COD (70–90%) and TKN (40–65%). HCW contributed 50–60% and 70–80% to COD and TKN removal respectively. The quantification of impacts on treatment efficiency and sustainability of DWTS was demonstrated at field-scale under high and moderate dynamic conditions.

Digitalisation for Water Sustainability: Barriers to Implementing Circular Economy in Smart Water Management

“Clean water and sanitation” is listed as one of the 17 United Nations’ Sustainable Development Goals and implementing circular economy principles in the water sector has been widely regarded as an important approach in achieving this goal. In the era of Industry 4.0, research and practice in the digitalisation of the water sector to create a smart water system have attracted increasing attention. Despite the growing interest, limited research has been devoted to how digital technologies might enhance circularity. In practice, smart water systems often fail to promote circularity in such aspects as water reuse and resources recovery. This paper aims to identify the main barriers to implementing circularity in the smart water management system in Zhejiang, China. The research adopts a mixed research method that includes a literature review to identify the potential barriers from the existing studies, a case study to determine the most critical barriers in practice, and a fuzzy Delphi method to reach a consensus on the crucial barriers. The research identified 22 main barriers to implementing circular economy in smart water management. The barriers are divided into three categories: infrastructure and economic, technology, and institution and governance. The results show that the barriers related to recycling technologies, digital technology know-how, and the lack of CE awareness raise the most concern. Our findings also indicate that experts are interested in the decentralized wastewater treatment system. This research provides significant insights that practitioners, researchers, and policymakers can use in developing and implementing digital-based CE strategies to reduce water scarcity and pollution.

The Life Cycle Environmental Performance of On-Site or Decentralised Wastewater Treatment Systems for Domestic Homes

There is little knowledge regarding the environmental sustainability of domestic on-site or decentralised wastewater treatment systems (DWWTS). This study evaluated six unique life cycle environmental impacts for different DWTTS configurations of five conventional septic tank systems, four packaged treatment units, and a willow evapotranspiration system. Similar freshwater eutrophication (FE), dissipated water (DW), and mineral and metal (MM), burdens were noted between the packaged and conventional system configurations, with the packaged systems demonstrating significantly higher impacts of between 18% and 56% for climate change (CC), marine eutrophication (ME), and fossils (F). At a system level, higher impacts were observed in systems requiring (i) three vs. two engineered treatment stages, (ii) a larger soil percolation trench area, and (iii) pumping of effluent. The evapotranspiration system presented the smallest total environmental impacts (3.0–10.8 lower), with net benefits for FE, ME, and MM identified due to the biomass (wood) production offsetting these burdens. Further analysis highlighted the sensitivity of results to biomass yield, operational demands (desludging or pumping energy demands), and embodied materials, with less significant impacts for replacing mechanical components, i.e., pumps. The findings highlighted the variation in environmental performance of different DWTTS configurations and indicated opportunities for design improvements to reduce their life cycle impacts.

Environmental Concern Priming and Social Acceptance of Sustainable Technologies: The Case of Decentralized Wastewater Treatment Systems.

According to a report by the World Economic Forum, the water crisis is the fourth most serious global risk to society. The apparent limitations of the hydraulic paradigm to solving this crisis are leading to a change in water management approaches. Recently, decentralized wastewater treatment systems have re-emerged as a partial solution to this problem. However, to implement these systems successfully, it is necessary not only to design this technology but also to have social support and willingness among citizens to use it. Previous studies have shown that these technologies are often perceived as being too costly, and people often do not consider the need for adopting them. However, it has also been pointed out that thinking about these technologies as a sustainable endeavor to reduce human impact on the environment can help to overcome the barriers to usage. Thus, we test whether priming environmental concerns before presenting information about decentralized wastewater treatment plants will increase acceptance of those technologies. In this study, we test whether priming environmental concerns can enhance the acceptance of decentralized wastewater treatment plants even when presenting disadvantages of the technology. In order to do so, we designed an experimental study with a sample of 287 people (85.7% women, M age=20, 28). The experimental design was 2 (priming the environmental concern vs. no priming)×2 (type of information: only advantages vs. advantages and disadvantages). The results showed that those in the environmental concern priming condition had more positive attitudes and behavioral intentions toward decentralized wastewater treatment plants than those in the control condition group. Participants who received only advantages information had a more positive perception toward the decentralized wastewater systems than in the condition, where disadvantages were present, but in the priming condition this difference was not significant. This implies that priming environmental concern helps to overcome the possible disadvantages that act as barriers to acceptance.

Persistence and removal of trace organic compounds in centralized and decentralized wastewater treatment systems

The persistence of trace organic chemicals in treated effluent derived from both centralized wastewater treatment plants (WWTPs) and decentralized wastewater treatment systems (DEWATS) is of concern due to their potential impacts on human and ecosystem health. Here, we utilize non-targeted analysis (NTA) with comprehensive two-dimensional gas chromatography coupled with time of flight mass spectrometry (GC × GC/TOF-MS) to conduct an evaluation of the common persistent and removed compounds found in two centralized WWTPs in the USA and South Africa and one DEWATS in South Africa. Overall, removal efficiencies of chemicals were similar between the treatment plants when they were compared according to the number of chemical features detected in the influents and effluents of each treatment plant. However, the DEWATS treatment train, which has longer solids retention and hydraulic residence times than both of the centralized WWTPs and utilizes primarily anaerobic treatment processes, was able to remove 13 additional compounds and showed a greater decrease in normalized peak areas compared to the centralized WWTPs. Of the 111 common compounds tentatively identified in all three influents, 11 compounds were persistent in all replicates, including 5 compounds not previously reported in effluents of WWTPs or water reuse systems. There were no significant differences among the physico-chemical properties of persistent and removed compounds, but significant differences were observed among some of the molecular descriptors. These results have important implications for the treatment of trace organic chemicals in centralized and decentralized WWTPs and the monitoring of new compounds in WWTP effluent.

Initial Stage in Designing Household Constructed Wetlands: Selection of a Suitable Aquatic Plant

Constructing centralized wastewater treatment plant systems to serve and control city sanitation requirements is vastly expensive in developing countries. Consequently, employing decentralized wastewater treatment systems through utilizing constructed wetlands (CWs) for individual households should be promoted. In this study, the most appropriate aquatic species planted in constructed wetlands were examined for treating greywater at the household level in humid tropical regions. Three different decorative aquatic plants (i.e., Echinodorus palaefolius, Typha latifolia, and Cyperus alternifolius) were compared based on their performances. Also, three similar wetlands having a total working volume of 158.42 liters with a gravel sand filter were used in this study. One day, a period was allocated for the hydraulic retention time (HRT), which corresponds to the applied hydraulic loading rate of 115.5- and 150.5-mm d-1 for the first and second experiments, respectively. The high percentage removal of 5-day biological oxygen demand (BOD5), along with an aesthetic green view and minimum maintenance of decorative plants, was employed as the selection criteria. In- situ measurements were also undertaken for pH, temperature, and total dissolved solids. The findings indicate that the most significant BOD5 removal was with the Cyperus alternifolius plants, which showed a very high BOD5 removal rate (91.18%). The Cyperus alternifolus species were more resistant in full direct sunlight conditions and adaptable to grow in temporarily or fully submerged conditions. These results, therefore, suggest that Cyperus alternifolius is the most suitable plant species for the treatment of greywater in household CWs in the tropics.

Woven-Fiber Microfiltration (WFMF) and Ultraviolet Light Emitting Diodes (UV LEDs) for Treating Wastewater and Septic Tank Effluent

Decentralized wastewater treatment systems enable wastewater to be treated at the source for cleaner discharge into the environment, protecting public health while allowing for reuse for agricultural and other purposes. This study, conducted in Thailand, investigated a decentralized wastewater treatment system incorporating a physical and photochemical process. Domestic wastewater from a university campus and conventional septic tank effluent from a small community were filtered through a woven-fiber microfiltration (WFMF) membrane as pretreatment for ultraviolet (UV) disinfection. In domestic wastewater, WFMF reduced TSS (by 79.8%), turbidity (76.5%), COD (38.5%), and NO3 (41.4%), meeting Thailand irrigation standards for every parameter except BOD. In septic tank effluent, it did not meet Thailand irrigation standards, but reduced TSS (by 77.9%), COD (37.6%), and TKN (13.5%). Bacteria (total coliform and Escherichia coli) and viruses (MS2 bacteriophage) passing through the membrane were disinfected by flow-through UV reactors containing either a low-pressure mercury lamp or light-emitting diodes (LEDs) emitting an average peak wavelength of 276 nm. Despite challenging and variable water quality conditions (2% < UVT < 88%), disinfection was predictable across water types and flow rates for both UV sources using combined variable modeling, which enabled us to estimate log inactivation of other microorganisms. Following UV disinfection, wastewater quality met the WHO standards for unrestricted irrigation.

The Potential of BIM in Disseminating Knowledge about Decentralized Wastewater Treatment Systems: Learning through the Design Process

Despite the low rate of sewer service coverage in developing countries, especially in small towns and rural areas, decentralized wastewater treatment systems (DEWATS) are alternatives to ensure public health. Nonetheless, understanding the physical or functional aspects of these system constructions remains difficult when there is no bibliography, a teaching professional, or even a prototype that allows technical conclusions about specific processes. Although resource combination in a BIM environment works as a facilitator to obtain compact and sustainable results, the purpose of this collaboration is not only to simplify the design process. This paper aims to propose a way to use BIM concepts as a learning tool throughout the modeling process. To do so, we developed a BIM template with specific DEWATS characteristics in order to provide not only information needed for construction, but also information that can favor learning. We measured how much the level of development (LOD) can influence learning about these systems during the design process, directing users to make the best implementation choices. The adoption of qualitative analysis of a questionnaire answered by three groups of professionals (general CADD software users, BIM software with generic template users, and BIM software with specific DEWATS template users) allowed us to identify differences among them, such as the number of DEWATS known, considered LOD, learning, and handicaps in the design of these systems. The results pointed out that the BIM tools can influence learning about new and unknown specific systems, which is directly related to the LOD of a model.

Improved and promising fecal sludge sanitizing methods: treatment of fecal sludge using resource recovery technologies

AbstractThe global challenges that face sustainable sanitation services in developing countries are the lack of fecal sludge (FS) management; this is due to the rapid urbanization and population growth as it generates enormous quantities of fecal sludge. The extensive use of unimproved sanitation technologies is one of the main reasons for environmental and public health concerns. In dispersed rural areas, isolated slums or in urban areas where a sewerage system is costly, a decentralized wastewater system can be used. Therefore centralized management of decentralized wastewater systems along with proper institutional framework treatment of fecal sludge can be used to enhance the economies of developing countries from resource recovery. The discovery of new ways to inactivate pathogens contained in human waste is key in improving access to sanitation worldwide and reducing the impact of conventional waste management processes on the environment. The entire FS management system should include on-site sanitary treatment methods, collection, and transportation of FS, treatment facilities as well as resource recovery or disposal of the treated end products. This review paper addresses the hygienization of fecal sludge and improved treatment technologies for safe reuse or disposal of the end products and the significant economic revenues attained from the treatments of fecal sludge.

Bio-Tower Application for Improvement of a Decentralized Waste Water Treatment System for Residential Applications–Reduction of Nonpoint Source Pollution by Nitrogen

The application of decentralized wastewater treatment system, also known as septic system is very common in suburban and rural areas with no access to centralized sewage treatment plants. Minimizing water pollution and the effects on wildlife and humans is of specific concern in rural and urban areas.
 A packed bio-tower addition to a 1000 gallon septic tank was tested under pilot conditions using municipal residential sewage. The septic tank packed bio-tower pilot system is able to reduce the NH3-N influent level of 16.5 mg/l to 24.0 mg/l by 77.3% to 96.7% at influent flow levels between1060 l/d (280 gal/d) and 3997 l/d (1056 gal/d). 
 Biochemical oxygen demand levels reduction was 97.0% from 280 mg/l to 8.5 mg/l. for a flow rate of 1060 l/d (280 gal/d).
 Research showed that a bio-tower addition to a septic system has the potential to improve the systems overall performance.

Mitigation of emerging pollutants and pathogens in decentralized wastewater treatment processes: A review.

Emerging pollutants (such as micropollutants, microplastics) and pathogens present in wastewater are of rising concern because their release can affect the natural environment and drinking water resources. In this decade, with increasing numbers of small-scale decentralized wastewater systems globally, the status of emerging pollutant and pathogen mitigation in the decentralized wastewater treatment processes has received more attention. This state-of-the-art review aims to discuss the mitigation efficiencies and mechanisms of micropollutants, microplastics, and pathogens in single-stage and hybrid decentralized wastewater treatment processes. The reviewed results revealed that hybrid wastewater treatment facilities could display better performance compared to stand-alone facilities. This is because the multiple treatment steps could offer various microenvironments, allowing incorporating several mitigation mechanisms (such as sorption, degradation, filtration, etc.) to remove complicated emerging pollutants and pathogens. The factors (such as system operation conditions, environmental conditions, wastewater matrix) influencing the removals of emerging pollutants from wastewater in these systems have been further identified. Nevertheless, it was found that very limited research work focused on synergised or conflicted effects of operation conditions on various emerging pollutants naturally present in the wastewater. Meanwhile, effective, reliable, and rapid analysis of the emerging pollutants and pathogens in the complicated wastewater matrix is still a major challenge.