Identifying prospective water plants for reducing nutrients and total coliform in sub-surface constructed wetlands with limited oxygen

A review on the main affecting factors of greenhouse gases emission in constructed wetlands

The mining industry is the major producer of acid mine drainage (AMD). The problem of AMD concerns at active and abandoned mine sites. Acid mine drainage needs to be treated since it can contaminate surface water. Constructed wetlands (CW), a passive treatment technology, combines naturally-occurring biogeochemical, geochemical, and physical processes. This technology can be used for the long-term remediation of AMD. The challenge is to overcome some factors, for instance, chemical characteristics of AMD such a high acidity and toxic metals concentrations, to achieve efficient CW systems. Design criteria, conformational arrangements, and careful selection of each component must be considered to achieve the treatment. The main objective of this review is to summarize the current advances, applications, and the prevalent difficulties and opportunities to apply the CW technology for AMD treatment. According to the cited literature, sub-surface CW (SS-CW) systems are suggested for an efficient AMD treatment. The synergistic interactions between CW components determine heavy metal removal from water solution. The microorganism-plant interaction is considered the most important since it implies symbiosis mechanisms for heavy metal removal and tolerance. In addition, formation of litter and biofilm layers contributes to heavy metal removal by adsorption mechanisms. The addition of organic amendments to the substrate material and AMD bacterial consortium inoculation are some of the strategies to improve heavy metal removal. Adequate experimental design from laboratory to full scale systems need to be used to optimize equilibria between CW components selection and construction and operational costs. The principal limitations for CW treating AMD is the toxicity effect that heavy metals produce on CW plants and microorganisms. However, these aspects can be solved partially by choosing carefully constructed wetlands components suitable for the AMD characteristics. From the economic point of view, a variety of factors affects the cost of constructed wetlands, such as: detention time, treatment goals, media type, pretreatment type, number of cells, source, and availability of gravel media, and land requirements, among others.

Surface water pollution is one of the serious environmental problems in urban centers ofNepal due to the discharge of untreated wastewater. Almost all conventional type wastewaterplants are not functioning well and practically not sustainable due to lack of regularmaintenance and high operation cost. To overcome this, Constructed Wetland (CW)technology for wastewater treatment arises as alternative technology in Nepal. Now, there are12 sub-surface flow CW systems in operation all over the country.This study aims to checking the efficiency and performance evaluation of three CW located atvarious locations in Nepal. The performance evaluation was conducted through collection ofwastewater samples from inlet and outlet sources of treatment plants and measuringsignificant water qualities determining physical and chemical parameters such as BiochemicalOxygen Demand (BOD), Chemical Oxygen Demand (COD), Hydrogen ion concentration(pH), Conductivity, Phosphorus, Total Suspended Solids (TSS), Total Dissolved Solids (TDS)and Total Solids (TS).The CW systems were found efficiently removing and reducing different pollutionparameters. Performance of CW system were excellent for Kathmandu University (KU) andMalpi International School (Malpi) where the efficiency levels ranged between 82% to 96%for BOD, 68% to 85% for COD, 91 % to 99% for TSS, 60% to 83% for TDS and for TS 84%to 92%. The performance efficiency was relatively lower for Thimi Community ScaleWastewater Treatment Plant (Thimi) where the efficiency levels was 56% for BOD, 64% forCOD, 17% for Conductivity, 88% for TSS, 59% for TDS and 80% for TS. The results showthat, the CW systems are useful and efficient for waste water treatment in growing urbanareas. They are cost effective and easy to maintain. It is recommended that CW system couldbe replicate in other growing urban areas.

Both bacteria and archaeal communities can play important roles in biogeochemical processes in constructed wetland (CW) system. However, the influence of plant type on microbial community in surface water CW remains unclear. The present study investigated bacterial and archaeal communities in five surface water CW systems with different plant species. The abundance, richness, and diversity of both bacterial and archaeal communities considerably differed in these five CW systems. Compared with the other three CW systems, the CW systems planted with Vetiveria zizanioides or Juncus effusus L. showed much higher bacterial abundance but lower archaeal abundance. Bacteria outnumbered archaea in each CW system. Moreover, the CW systems planted with V. zizanioides or J. effusus L. had relatively lower archaeal but higher bacterial richness and diversity. In each CW system, bacterial community displayed much higher richness and diversity than archaeal community. In addition, a remarkable difference of both bacterial and archaeal community structures was observed in the five studied CW systems. Proteobacteria was the most abundant bacterial group (accounting for 33-60%). Thaumarchaeota organisms (57%) predominated in archaeal communities in CW systems planted with V. zizanioides or J. effusus L., while Woesearchaeota (23 or 24%) and Euryarchaeota (23 or 15%) were the major archaeal groups in CW systems planted with Cyperus papyrus or Canna indica L. Archaeal community in CW planted with Typha orientalis Presl was mainly composed of unclassified archaea. Therefore, plant type exerted a considerable influence on microbial community in surface water CW system.

This paper describes a two-year performance evaluation of four different constructed wetland (CW) treatment systems designed by IRIDRA Srl, located in central Italy. All four CW systems were established to treat wastewater effluent from different tourist activities: (1) one single-stage CW for secondary treatment of domestic wastewater (30 p.e.) at a holiday farm site; (2) a hybrid compact system consisting of two stages, a horizontal flow (HF) system followed by a vertical flow (VF) system for the secondary treatment of effluent from a 140 p.e. tourist resort; (3) a single-stage vertical flow (VF) CW for a 100 p.e. mountain shelter; and (4) a pair of single-stage, HF CWs for the secondary treatment of segregated grey and black water produced by an 80 p.e. camping site. These tourism facilities are located in remote areas and share some common characteristics concerning their water management: they have high variability of water consumption and wastewater flow, depending on the season, weather and weekly regularities; they have no connection to a public sewer and most sites are located in a sensitive environment. Total suspended solids (TSS), chemical oxygen demand (COD), biochemical oxygen demand (BOD5), ammonium (N-NH4+), nitrate (N-NOx), total nitrogen (Ntot), total phosphorus (Ptot), total coliform (TC), faecal coliform (FC), E. coli removal efficiencies for all four CW systems are presented. The results from this study demonstrate the potential of CWs as a suitable technology for treating wastewater from tourism facilities in remote areas. A very efficient COD reduction (83-95%) and pathogen elimination (3-5 logs) have been achieved. Furthermore, the CWs are easily maintained, robust (not sensitive to peak flows), constructed with local materials, and operate with relatively low cost.

Growth and biomass production of different plant species in two different constructed wetland systems in Sicily

The depth of substrate in constructed wetlands (CWs) has a significant effect on the construction investment and the purification performance of CWs. In this study, a pilot scale CW system was operated in a domestic sewage treatment plant in Xi’an, China. The experimental systems included three-series CWs systems with substrate depths of 0.1m, 0.3 m and 0.6 m, respectively. Each series was composed of a hydroponic ditch, a horizontal subsurface flow CW and a vertical flow CW. The effluent from the primary clarifier in the sewage treatment plant was intermittently conducted to the wetlands at a flow rate of 0.3 m3/d. The hydraulic loading rate of each CWs system was regulated at 0.1 m3/m2.d and the hydraulic retention time was 3 days. Canna indica L. was planted both in the hydroponic ditches and the CWs systems. Results showed that the highest removal efficiency of NH+ 4-N and TP was obtained in the hybrid CW with 0.1 m substrate depth. The average removal efficiency for NH+ 4-N and TP were 90.6 % and 80.0 %, respectively. The highest average removal efficiency of COD was obtained in hybrid CWs system with 0.6 m substrate depth. Therefore, a simultaneous removal of COD and nutrients can be achieved through the combination of different wetlands using different substrate depths. In addition, the substrate depth presents significant effects on the concentration of DO and root growth characteristics of canna in the system. As a result, the highest concentration of DO (>2 mg/L) and the highest amount of roots production were achieved in the 0.1 m substrate depth horizontal and vertical flow CWs.

Wetland’s concept are becoming a popular alternative to traditional technologies for processing wastewater from domestic as well as industrial, especially for tertiary treatment of wastewater. Constructed Wetland (CW) is the assemblage which performs the treatment of wastewater by the process of unit operation techniques using natural process. It helps in achieving effective treatment efficiency in a sustainable manner. Due to an increase in wastewater loading, insufficient arrangement of sterilization and sewage treatment prompts in ecological impact and contamination of water bodies. It leads to water stress and depletion of good quality of ground water. Therefore, wastewater and reusing techniques will be essential in the coming days to overcome the crisis. CW is an effective alternative to overcome this situation. CW systems seem to be viable alternative in treating predominantly domestic wastewater and some type of industrial wastewater. In this method, the readied wet soil is successful for eliminating natural and suspended solids, while the evacuation of nitrogen is moderately low, however, can be improved by utilizing a combination of various sorts of wet soil arranged to satisfy water system reusing guidelines. In this research study, feasibility analysis has been carried out with domestic wastewater and industrial wastewater to ascertain the efficiency of CW in treating the wastewater and also the problems and limitations in handling the same was also assessed. General instruction regarding CW operation built for the treatment of specific wastewater types also ascertained in this research study. The important points that should always include suggestions about the pre-treatment stage, plants, and permeable media and built wetland operation strategies, etc., are discussed in this research paper. CW with integrated/hybrid model by linking both horizontal and vertical flow units was fabricated in a lab-scale hybrid wetland unit for treating the wastewater. Based on several trail study, it was observed that CW are very effective in treating organic wastewater. The treatment efficiency of some of the common parameter like Biological Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) was around 70–80%. Several researchers have also proved that this one of the viable alternative technique for urban environment and semi-urban environment were availability of space for developing the CW unit is not a problem. It was evident from the study that CW is effective sustainable technology for the near future to solve the water crisis and to implement 3R concept in wastewater treatment.KeywordsWetlandsConstructed wetlandsWastewaterHybrid wetlandOrganic wastewater

Removal of selected emerging PPCP compounds using greater duckweed (Spirodela polyrhiza) based lab-scale free water constructed wetland

Hybrid constructed wetlands system for domestic wastewater treatment under tropical climate: Effect of recirculation strategies on nitrogen removal

The wine industry generates large volumes of wastewater originating from various processes and operations carried out during wine production. Winery wastewater (WWW) is characterized by highly variable flows and loadings. Indeed, more than half of the annual wastewater flow and load is produced during the vintage season, when grape is harvested and grape juice is handled and managed. Spain is one of the world's largest wine-producing countries. Nevertheless, in most of the Spanish wineries wastewater is still not properly treated or managed. In this context, constructed wetlands (CWs) constitute a suitable alternative to conventional systems (e.g. activated sludge systems, membrane bioreactors) for WWW treatment due to their low cost, low energy requirement, easy operation and maintenance and their integration into the landscape. From a technical point of view, full-scale applications of CWs have demonstrated to reduce more than 90% of the organic pollutants and solids from WWW producing suitable water for multiple reuse purposes such as irrigation. Moreover, primary treatments of CWs can produce sludge which can be stabilised in sludge treatment wetlands (STWs) producing biofertilizers and soil conditioners. The production of reclaimed water and biofertilizers from WWW can promote the circular economy in the wine sector increasing their sustainability. Although CWs application in the wine sector has been widely proved from a technical point of view, there are still no studies which assess and quantify their environmental benefits in the context of circular economy. This PhD Thesis aims to assess and quantify the environmental benefits of CWs for WWW treatment compared with existing and conventional solutions. To address this objective, a life cycle assessment (LCA), greenhouse gas (GHG) emissions measurements and a carbon footprint (CFP) evaluation were carried out comparing CW systems with conventional technologies and other existing alternatives (i.e. activated sludge system and third-party management). This research has been carried out in the frame of the WETWINE project (http://wetwine.eu/) which aimed to promote environmentally friendly and innovative solutions to treat effluents produced by wine industries in the South-West of Europe. Thus, this research was based on the study of different full-scale systems implemented in wineries located in Galicia (Spain), Portugal and Southern France. In particular, a CW system has been designed and implemented in a winery located in Galicia, in which experimental activities have been carried out. The results of the LCA showed that the environmental impacts of CWs were between 1.5 and 180 times lower than the third-party management alternative and between 1 and 10 times lower than the activated sludge system. GHG emissions (carbon dioxide (CO2), nitrous oxide (N2O) and methane (CH4)) were monitored in a CW and an activated sludge systems using an on-site Fourier transform infrared spectroscopy (FTIR) gas analyser. Results highlighted that surface emission rates from the CW system were lower than those released by the activated sludge system. Furthermore, seasonally, daily and instantaneous variability in emissions as well as spatial variability were recorded and reported. The CFP of the CW system was up to 42 times lower in comparison with the third-party management and up to 4 times lower than the activated sludge system. Finally, an economic assessment was conducted. CWs can reduce winery costs associated with WWW treatment up to 50% for the construction and up to 98% for the operation and maintenance. Finally, this PhD Thesis assessed and quantified, for the first time, the environmental benefits of CWs for WWW treatment. CWs were proven to be a sustainable solution for WWW and sludge treatment, since they are an environmentally friendly and cost-effective alternative which can promote the circular economy in wineries enabling sludge and water treatment and reuse on-site. La indústria del vi genera grans volums d’aigües residuals procedents de diversos processos i operacions realitzats durant la producció del vi. Les aigües residuals de celler (ARC) es caracteritzen per tenir uns cabals i càrregues molt variables. De fet, més de la meitat del cabal i càrrega produïts durant l’any es concentren durant l’època de verema, quan es recull el raïm i es produeix el suc de raïm. Espanya és considerada un dels països amb major producció de vi. No obstant això, a la majoria dels cellers Espanyols les aigües residuals encara no són tractades o gestionades adequadament. En aquest context, els aiguamolls construïts (AC) són una alternativa als sistemes convencionals (p. ex. Sistema de fangs activats, bioreactors de membrana) per al tractament de les ARC ja que tenen un baix cost, baix requeriment d’energia, fàcil operació i manteniment i una bona integració al paisatge. Des d’un punt de vista tècnic, s’ha demostrat que les aplicacions d’AC a escala real redueixen més d’un 90% dels contaminats orgànics i dels sòlids de les ARC produint aigua apta per múltiples usos de reutilització com el reg. A més, el tractament primari dels AC pot produir fangs que poden ser estabilitzats a aiguamolls de tractament de fangs per a produir biofertilitzants i adobs orgànics. La producció d’aigua regenerada i biofertilitzants a partir de les ARC pot promoure l’economia circular al sector vitivinícola augmentant la seva sostenibilitat. Tot i que l’aplicació dels AC al sector vitivinícola ha estat àmpliament provada des d’un punt de vista tècnic, encara no existeixen estudis que avaluïn i quantifiquin els seus beneficis ambientals en el context de l’economia circular. Aquesta tesi doctoral té com a objectiu avaluar i quantificar els beneficis ambientals dels AC per al tractament de les ARC en comparació amb les solucions existents i convencionals. Per abordar aquest objectiu, s’ha dut a terme una avaluació del cicle de vida (ACV), mesures de gasos d’efecte hivernacle (GEH) i una avaluació de la petjada de carboni comparant els sistemes d’AC amb tecnologies convencionals i altres alternatives existents (és a dir, el sistema de fangs activats i la gestió per tercers). Aquesta investigació s’ha realitzat en el marc del projecte WETWINE (http://wetwine.eu/) que va tenir com a objectiu promoure solucions innovadores i respectuoses amb el medi ambient per al tractament d’efluents produïts per la industria vitivinícola al sud-oest d’Europa. Per això, aquesta investigació s’ha basat en diferents sistemes a escala real implementats a bodegues ubicades a Galícia (Espanya), Portugal i sud de França. En particular, s’ha dissenyat i implementat un sistema d’AC a un celler situat a Galícia, on s’ha dut a terme activitats experimentals. Els resultats de l'ACV van mostrar que els impactes ambientals dels AC eren entre 1,5 i 180 vegades inferior que la gestió per tercers i entre 1 i 10 vegades inferior que el sistema de fangs activats. Les emissions de GEH (és a dir, diòxid de carboni (CO2), òxid nitrós (N2O) i metà (CH4)) es van monitoritzar en un sistema de fangs activats i AC utilitzant un analitzador de gasos d'espectroscòpia infraroja per transformada de Fourier (FTIR) in situ. Els resultats van destacar que les taxes d'emissió superficial del sistema d'AC van ser més baixes que les generades pel sistema de fangs activats. A més, es va registrar i documentar variabilitat estacional, diària i instantània a les emissions, així com variabilitat espacial. La petjada de carboni del sistema d'AC era fins a 42 vegades inferior en comparació amb la gestió per tercers i fins a 4 vegades inferior al sistema de fangs activats. Finalment, aquesta tesi ha avaluat i quantificat, per primera vegada, els beneficis ambientals dels AC per al tractament d’ARC. S’ha demostrat que són una solució sostenible per al tractament d’aigües residuals i fangs a les bodegues ja que són una alternativa respectuosa amb el medi ambient i rentable econòmicament que pot promoure l’economia circular permetent el tractament i reutilització de fangs i aigües in situ. Els resultats de la investigació d’aquesta tesi poden ajudar a impulsar la implementació dels AC al sector vitivinícola, així com a difondre els seus beneficis ambientals per guanyar més acceptació social.

Although constructed wetlands (CWs) are widely used around the world with various substrates, the mechanisms of how these modified substrates affect wastewater treatment are still unknown. In this study, CW microcosms were established with and without ceramsite as a substrate, and the wastewater treatment efficiencies were evaluated during 71 days of incubation. Using the 16S rRNA high-through sequencing, the mechanisms of how CW substrate changed the microbial community was quantified. The results showed that compared to soil as substrate, the use of ceramsite as substrate material enhanced the removal of pollutants from CW systems, particularly under a short retention time (1.5-day) condition. There were more beneficial microorganism groups (nitrogen, sulfur, phosphate) in the ceramsite CW system than the non-ceramsite CW system, particularly in the bottom layers. Moreover, the CW with ceramsite substrate had more nitrification function. All of these results suggested that the ceramsite CW system enhanced the removal of pollutants because it increased the concentration of key microbes that are necessarily for nutrient cycles.

In aquaculture, constructed wetland (CW) has recently attracted attention for use in effluent purification due to its low running costs, high efficiency and convenient operation,. However, less data are available regarding the long-term efficiency of farm-scale CW for cleaning effluents from inland freshwater fish farms. This study investigated the effectiveness of CW for the removal of nutrients, organic matter, phytoplankton, heavy metals and microbial contaminants in effluents from a blunt snout bream (Megalobrama amblycephala) farm during 2013–2018. In the study, we built a farm-scale vertical subsurface flow CW which connected with a fish pond, and its performance was evaluated during the later stage of fish farming. The results show that CW improved the water quality of the fish culture substantially. This system was effective in the removal of nutrients, with a removal rate of 21.43–47.19% for total phosphorus (TP), 17.66–53.54% for total nitrogen (TN), 32.85–53.36% for NH4+-N, 33.01–53.28% NH3-N, 30.32–56.01% for NO3−-N and 42.75–63.85% for NO2−-N. Meanwhile, the chlorophyll a (Chla) concentration was significantly reduced when the farming water flowed through the CW, with a 49.69–62.01% reduction during 2013–2018. However, the CW system only had a modest effect on the chemical oxygen demand (COD) in the aquaculture effluents. Furthermore, concentrations of copper (Cu) and lead (Pb) were reduced by 39.85% and 55.91%, respectively. A microbial contaminants test showed that the counts of total coliform (TC) and fecal coliform (FC) were reduced by 55.93% and 48.35%, respectively. In addition, the fish in the CW-connected pond showed better growth performance than those in the control pond. These results indicate that CW can effectively reduce the loads of nutrients, phytoplankton, metals, and microbial contaminants in effluents, and improve the water quality of fish ponds. Therefore, the application of CW in intensive fish culture systems may provide an advantageous alternative for achieving environmental sustainability.

Constructed wetland (CW) could be an attractive alternative for wastewater treatment in Sarawak, particularly in rural areas with low population densities, due to its advantage of being cost- and energy-effective, as well as its simplicity in operation and maintenance. CW has been widely used as a decentralized wastewater treatment system in developed and developing countries to treat various types of wastewater, including domestic sewage, surface runoff, agricultural wastewater, and sewage sludge. However, CW is still a relatively new wastewater treatment method in Sarawak, where only two CW systems are available in the entire state. This paper presents a review of existing CW systems treating domestic sewage and a pilot-scale study of subsurface flow CW system treating septage in Sarawak. In addition, the cost-effectiveness, environmental impact, public perception, and legislative requirement of CW systems are discussed in the context of wastewater management policies in Sarawak. This study gains important insight into the feasibility of CW systems as a long term solution to wastewater management in the rural areas of Sarawak.

A review on the fate of micro and nano plastics (MNPs) and their implication in regulating nutrient cycling in constructed wetland systems