Significance of Primary Treatment Selection in the Efficiency of Wastewater Treatment in Constructed Wetlands (CWs)

This research explores strategies to enhance the efficiency of secondary treatment in Vertical Flow Constructed Wetlands (CW) in Montenegro. The focus is on selecting appropriate primary treatment methods alongside three distinct substrate types to improve wastewater treatment efficacy. The study examines the combination of two primary treatments with different substrate types in constructed wetlands (CW1, CW2, and CW3). The primary treatments include the existing wastewater treatment plant (WWTP) in Podgorica, involving coarse material removal through screens, inert material separation in aerated sand traps, and sediment and suspended matter removal in primary sedimentation tanks. The Extreme Separator (ExSep) was employed to evaluate its efficacy as a primary treatment method. The research demonstrates that the efficiency of CW can be significantly enhanced by selecting suitable primary treatment methods and substrates in Podgorica’s conditions. The most promising results were achieved by combining ExSep as a primary treatment with secondary treatment in CW-3. The removal efficiencies after CW3 for COD, BOD, and TSS exceeded 89%, 93%, and 91%, respectively. The outcomes underscore the significance of primary treatment in mitigating pollutant loads before discharge into the constructed wetlands, emphasizing potential areas for further optimization in wastewater treatment practices to enhance environmental sustainability and water quality management.

Efficiency and effectiveness of systems for the treatment of domestic wastewater based on subsurface flow constructed wetlands in Jarabacoa, Dominican Republic

Constructed wetlands(CwW)are well known nature-based systems for water treatment.This study evaluated the efficiency and effectiveness of seven domestic wastewater treatment systems based on horizontal flow CWs in Jarabacoa,the Dominican Republic.The results showed that the CWs were efficient in reducing the degree of contamination of wastewater to levels below the Dominican wastewater discharge standards for parameters such as the 5-day biochemical oxygen demand(BOD5)and chemical oxygen demand,but not for the removal of phosphorus and fecal coliforms.In addition,a horizontal flow subsurface wetland in the peri-urban area El Dorado was evaluated in terms of the performance of wastewater treatment in tropical climatic conditions.The concentrations of heavy metals,such as zinc,copper,chromium,and iron,were found to decrease in the effluent of the wetland,and the concentrations for nickel and manganese tended to increase.The levels of heavy metals in the effluent were lower than the limit values of the Dominican wastewater discharge standards.The construction cost of these facilities was around 200 USD per population equivalent,similar to the cost in other countries in the same region.This study suggested some solutions to the improved performance of CWs:selection of a microbial flora that guarantees the reduction of nitrates and nitrites to molecular nitrogen,use of endemic plants that bioaccumulate heavy metals,combination of constructed wetlands with filtration on activated carbon,and inclusion of water purification processes that allow to evaluate the reuse of treated water.

Significance of Substrate Selection in the Efficiency of Wastewater Treatment in Constructed Wetlands (CWs)

Constructed wetlands (CWs) can achieve a high-quality wastewater treatment and a quality that meets the prescribed standard, defined by legislation on wastewater discharge. A limitation in the application of constructed wetlands (CWs) is the large area requirement, which limits their application. The subject matter of this research is to check the possibility of improving the efficiency of wastewater treatment and reducing the required area for constructed wetlands (CWs) by using an adequate substrate under the conditions found in Montenegro. In the described experiment, the constructed wetlands (CW) have a vertical flow system and play the role of a secondary wastewater treatment, receiving water from the existing WWTP in Podgorica after the primary treatment. These vertical flow systems reflect experience with the use of similar systems in Slovenija, Austria and Italy. Measurements to date show that the substrate plays an important role and that wastewater treatment efficacy varies significantly with respect to the type of substrate when used under the conditions available in Montenegro.

Treatment and utilization of septic tank effluent using vertical-flow constructed wetlands and vegetable hydroponics

Vertical flow constructed wetlands is a typical ecological sanitation system for sewage treatment. The removal rates for COD, BOD 5, SS, TN, and TP were 60%, 80%, 74%, 49% and 79%, respectively, when septic tank effluent was treated by vertical flow filter. So the concentration of COD and BOD\-5 in the treated effluent could meet the quality standard for irrigation water. After that the treated effluent was used for hydroponic cultivation of water spinach and romaine lettuce, the removal efficiencies of the whole system for COD, BOD\-5, SS, TN and TP were 71 4%, 97 5%, 96 9%, 86 3%, and 87 4%, respectively. And it could meet the integrated wastewater discharge standard for secondary biological treatment plant. It was found that using treated effluent for hydroponic cultivation of vegetables could reduce the nitrate content in vegetables. The removal rates for total bacteria and coliform index by using vertical flow bed system with cinder substrate were 80%—90% and 85%—96%, respectively.

Performance evaluation of hybrid constructed wetlands for the treatment of municipal wastewater in developing countries

In developing countries,high cost of conventional wastewater treatment is a major hindrance in its application.Constructed wetlands(CWs)offer low-cost and effective solution to this issue.The current study aimed to evaluate an innovative maneuver of CWs i.e.hybrid flow constructed wetlands(HCWs)for municipal wastewater(MWW).The HCWs included two lab scale CWs;one horizontal and one vertical,in series.Local plant species were used.HCWs were operated in both,batch and continuous mode.Batch mode was used to(1)optimize detention time and(2)find pollutants removal efficiency.Continuous operation(at batch optimized retention time)was carried out for the evaluation of mass removal rate,r(g·m-2·d-1),volumetric rate constant,Kv(per day)and areal rate constant,Ka(m·d-1).Among two local plants tested,Pistia stratiotes gave better removal efficiency than Typha.Optimum detention time in HCWs was found to be 8 days(4+4 each).The optimum COD,BOD,TSS,TKN and P removal observed for Pistia stratiotes planted HCWs was 80%,84%,82%,71%and88%respectively.Effluent standards for COD,BOD and TSS were met at optimum conditions.The values of Kaand Kv demonstrated that more removal occurred in vertical flow as compared to horizontal flow CW.

Application of Constructed Wetlands on Wastewater Treatment for Aquaculture Ponds

A group of constructed wetlands （CWs） were applied to the recirculating aquaculture system. This study assessed the performance of CWs in treating the aquaculture wastewater, examined the water quality condition of aquaculture ponds and the growth and the survival rate of ＂target＂ species （Ictalurus punctatus and Megalobrama amblycephala）. The results showed that CWs were effective on reducing the concentrations of 5-day biochemical oxygen demand （BOD5, at 70.5%）, total suspended solids （TSS, at 81.9%）, chlorophyll a （Chl-a, at 91.9%）, ammonium （NH4^＋, at 61.5%） and nitrate nitrogen （NOa-N, at 68.0%）. Effect of CWs on phosphate （PO43 -P） removal was relatively lower （at 20.0%）. The concentrations of BODs, TSS, Chl-a, NH4^＋ and TN, TP in the recirculating culture pond were significantly lower than that in the control pond（ p〈0.05 ）. CWs could help to increase total yield, survival rate of the ＂target＂ species and significantly decrease feed conversion ratio （ p〈0.05 ）.

Optimization of Four Kinds of Constructed Wetlands Substrate Combination Treating Domestic Sewage

Based on the static and dynamic experiments, this paper has analyzed the adsorbing capacity for domestic wastewater pollutant （COD, NH4^＋-N and TP） of four kinds of constructed wetlands substrate which were fly ash, hollow brick crumbs, coal cinder and activated carbon pellets in single and combined condition. In the static experiments, the adsorbing capacity of four substrates all grew as the adsorbing dose increased. In adsorbing COD, each substrate＇s adsorbing capacity rises with the adsorbing dosage. Simultaneously, experiments show that all the adsorption of the four kinds of substrate for COD, NH4^＋-N and TP follows the Freundich Rule. The dynamic experiment demonstrated that the adsorbing capacity of combined substrates is bigger than that of single substrate. Fly ash in combination with small coal cinder adsorbs COD the best, while it takes in NH4^＋-N and TP the best when working with hollow brick crumbs. The combination of the two raises the removal rates up to 89% and 81% respectively. Given high cost and low adsorbing effect, activated carbon is not a suitable candidate for constructed wetlands substrate.

Modeling on Residence Time Distribution in Subsurface Flow Constructed Wetlands by Multi Flow Dispersion Model

As an important design factor for constructed wetlands,hydraulic retention time and its distribution will affect the treatment performance.Instantaneously injected sodium chloride tracers were used to obtain residence time distributions of the lab scale subsurface flow constructed wetland.Considering the presence of trailing and multiple peaks of the tracer breakthrough curve,the multi flow dispersion model(MFDM)was used to fit the experimental tracer breakthrough curves.According to the residual sum of squares and comparison between the experimental values and simulated values of the tracer concentration,MFDM could fit the residence time distribution(RTD)curve satisfactorily,the results of which also reflected the layered structure of wetland cells,thus to give reference for application of MFDM to the same kind of subsurface flow constructed wetlands.

Contributions of Different Wetland Plants to Nitrogen and Phosphorus Removal in Constructed Wetlands

Constructed wetlands with Cyperus altrnlifolius,Pennisetum sinese Roxb and elephant grass as vegetation were built to study the nitrogen and phosphorous removal from domestic sewage in cold climate.It was found that these three plants could all grow slowly and stably under low temperature stress in winter,and the biomass,nitrogen and phosphorus absorption characteristics and absorbing capacity of the three plants were different.The growth rate and biomass were as follows:P.sinese Roxb>elephant grass>C.altrnlifolius,and these three plants could be used as winter wetland decontamination plants in Southwest China;the absorption characteristics of nitrogen and phosphorus in different tissues of the three plants were as follows:nitrogen content in leaf>nitrogen content in stem,phosphorus content in stem>phosphorus content in leaf;the removal of total nitrogen(TN)by three plants in the wetland was ranged form 4.3%to 7.8%,and the removal of total phosphorus(TP)was ranged from 3.3%to 5.3%.Different plants had different absorption effects on nitrogen and phosphorus.There was a significantly positive correlation between plant nitrogen and phosphorus accumulation and biomass,and nitrogen removal rate in wetland showed a significantly positive correlation with biomass.

Phosphorus and Nitrogen Removal by Saturated Vertical-Flow Constructed Wetlands (SVCWs) Type Micro-Pilot Using Shale from Ivory Coast as a Substrate

This study evaluates the performance of shale from Ivory Coast used as substrate in vertical-flow constructed wetlands in removal of phosphates and nitrogen. The pilot-scale artificial wetland has been duplicated: filter planted with Panicum maximun and unplanted. They were set up outdoors, and fed with a municipal wastewater. The wetlands have been fed with three batches per week (intermittent) over a period of 3 months. During the operation period, the hydraulic residence time (HRT) 52 h was used, while wastewater temperatures varied from about ~33°C. The removal performance of the constructed wetland units was very good, since it reached on an average 98%, 89.4%, 89.4%, 84%, 80%, 84.8% and 92% for TSS, DOC, BOD5, , TKN, TP and respectively. In addition, the vegetation did not demonstrate superior performance to unplanted controls. Therefore, this study focuses on the role of shale in the phosphorus and nitrogen removal from wastewater by constructed wetland.

Purification Effect of Constructed Wetlands for Treating River Water Flowing from Phosphate Mine Areas into Fuxian Lake

[ Objective] The study aimed at discussing the purification effect of constructed wetlands for treating river water flowing from phosphate mine areas into Fuxian Lake. [Method] The running parameters of the constructed wetlands were investigated for one year, and the purification effect of the constructed wetlands for treating the sewage from phosphate mine areas was analyzed. [Result] With the aid of the constructed wet- land, the average removal rates of total nitrogen （TN）, total phosphorus （TP） and CODcr were 52%, 32% and 54%, and the removal effects were best when the designed hydraulic load was 0.67 m3/（ m2 · d）. Running stably for six years, the constructed wetlands had advantages of no power, low resistance and high removal rate. [ Conclusion] The constructed wetlands reduced the load of pollutants from phosphate mine areas into Fuxian Lake effectivelv, which Dlaved important roles in the Drotection of water aualitv of Fuxian Lake.

Effect of carbon source on the denitrification in constructed wetlands

The ability of constructed wetlands with different plants in nitrate removal were investigated. The factors promoting the rates of denitrification including organic carbon, nitrate load, plants in wetlands, pH and water temperature in field were systematically investigated. The results showed that the additional carbon source （glucose） can remarkably improve the nitrate removal ability of the constructed wetland. It demonstrated that the nitrate removal rate can increase from 20% to more than 50% in summer and from 10% to 30% in winter, when the nitrate concentration was 30-40 rag/L, the retention time was 24 h and 25 mg/L dissolved organic carbon （DOC） was ploughed into the constructed wetland. However, the nitrite in the constructed wetland accumulated a little with the supply of the additional carbon source in summer and winter, and it increased from 0.15 to 2 mg/L in the effluent. It was also found that the abilities of plant in adjusting pH and temperature can result in an increase of denitrification in wetlands. The seasonal change may also impact the denitrification.

Clogging processes caused by biofilm growth and organic particle accumulation in lab-scale vertical flow constructed wetlands

The accumulation of organic matter in substratum pores is regarded as an important factor causing clogging separately in the subsurface flow constructed wetlands.In this study,the developing process of clogging caused by biofilm growth or organic particle accumulation instead of total organic matter accumulation was investigated in two groups of lab-scale vertical flow constructed wetlands（VFCWs）,which were fed with glucose（dissolved organic matter） and starch（particulate organic matter） influent.Results showed that the growth of biofilms within the substratum pores certainly caused remarkable reduction of effective porosity,especially for the strong organic wastewater,whereas its influence on infiltration rate was negligible.It was implied that the most important contribution of biofilm growth to clogging was accelerating the occurrence of clogging.In comparison with biofilm growth,particles accumulation within pores could rapidly reduce infiltration rate besides effective porosity and the clogging occurred in the upper 0-15 cm layer.With approximately equal amount of accumulated organic matter,the effective porosity of the clogged layer in starch-fed systems was far less than that of glucose-fed systems,which indicated that composition and accumulation mode in addition to the amount of the accumulated organic matter played an important role in causing clogging.

Characteristics of the microbial communities in the integrated vertical-flow constructed wetlands

Microorganisms play an important role in removing pollutants from constructed wetlands. We investigated the microbial characteristics in a novel integrated vertical-flow constructed wetland （IVCW）, which has been in operation in Wuhan, China since 1998. We used phospholipid fatty acid （PLFA） and amoA gene to analyze the structure and diversity of the microbial community within the IVCW. PLFA results suggested that the amount of bacterial PLFA was significantly higher than that of fungal PLFA, but the total microbial biomass represented by PLFA index was low in the system. Microbial spatial distribution showed significantly higher bacterial （both G^＋ and G^-） and fungal biomass in the surface than in the subsurface layers. The ratios of monounsaturated to branched PLFA demonstrated that an anaerobic layer sandwiched by two aerobic layers existed in the IVCW, consistent with the redox potential results. Analysis of the amoA revealed the presence of Nitrosomonas-like sequences in the surface substrate of the downflow chamber and apparent diversities of ammonia-oxidizing bacteria in the system. These results suggest that microorganisms, despite their relatively low biomass, have inhabited the IVCW, and the results will offer some valuable information on microbe to system designers and managers.

Effect of Different Factors on Nitrogen Removal Rate in Constructed Wetlands

Factors affecting total nitrogen(TN) removal rates in constructed wetland were investigated by intermittent operation in the subsurface flow(SSF) constructed wetland system.The results demonstrated that removal rates of TN increased with the rising of TN pollution load(1.40-12.40 g/m2) when the retention time was determined by 60% TN removal efficiency(n=180,p<0.05) in SSF wetlands.The maximum TN removal rate was 1.71 g/(m2·d) in SSF Phragmites australis-soil-slag system.TN removal rates were affected by total phosphorus load in case of higher TN load.TN removal rates in SSF Phragmites australis wetlands were greater than that in SSF Calamagrostis angustifolia wetlands at the same experimental cycle.Effect of wetland substrates on TN removal rates varied with the pollutants loading in SSF constructed wetland system,plant species and plant-growing period.

Distribution characteristics of ammonia-oxidizing bacteria in the Typha latifolia constructed wetlands using fluorescent in situ hybridization(FISH)

A molecular biology method, fluorescent in situ hybridization（FISH）, in which the pre-treatment was improved in allusion to the media of the constructed wetlands（CW）, e.g. the soil and the grit, was used to investigate the vertical distribution characteristics of ammonia-oxidizing bacteria（AOB） quantity and the relation with oxidation-reduction potential（ORP） in the Typha latifolia constructed wetlands under three different Ioadings in summer from May to September. Results showed that the quantity of the AOB decreased in the Typha latifolia CW with the increase of vertical depth. However, the AOB quantity was 2-4 times the quantity of the control in the root area. Additionally, ORP in the rhizosphere was found to be higher than other areas, which showed that Typha latifolia CW was in an aerobic state in summer when using simulated non-point sewage at the rural area of Taihu Lake in China and small town combined sewage.

Employing Constructed Wetlands to Sustainably Manage Nutrient-Bearing Water: A Review with an Emphasis on Soil Behavior and Effluent Nutrient Reduction

Constructed wetlands are engineered structures designed to simulate processes of natural wetlands to mitigate anthropogenic organic and inorganic materials to shelter soil and water resources. This review focuses on the global interest in constructed wetland application to sustain soil health and water quality and water abundance. Engineering criterion remains a function of nutrient chemistry and load with suitability factors including the local soil and hydrogeology constraints, climate, vegetation selection, the degree of required influent improvement, and reactor types and sizes. Future research needs to focus on: 1) reactor designs criteria, 2) the biology of the microbial community, 3) selection criteria for native vegetation, and 4) criteria to reapply treated water to foster land productivity, especially for region’s experiencing water deficiencies.

Simultaneous enhanced ammonia and nitrate removal from secondary effluent in constructed wetlands using a new manganese-containing substrate

Constructed wetlands(CWs)are widely used to treat secondary effluent.However,simultaneously removing ammonia(NH_(4)^(+)-N)and nitrate(NO_(3)^(–)–N)is challenging because of insufficient oxygen and carbon sources.In this study,a novel composite material(MPCM)comprising MnO2 and polycaprolactone was developed as a substrate for CWs to enhance the synchronous removal of NH_(4)^(+)–N and NO_(3)^(–)–N.The CWs with a higher MPCM content(H-CW),lower MPCM content(LCW),and controlled CW(C-CW)exhibited average NH_(4)^(+)–N removal efficiencies of 75.69%,70.49%,and 52.40%,respectively.The 15N isotope tracking technique showed that NH_(4)^(+)–N removal was attributed to anaerobic ammonia oxidation mediated by MnO2 reduction(Mnammox),which accounted for 17.16%–27.24%of the NH_(4)^(+)–N removal in the composite material layers(0–20 cm)of the H-CW and L-CW.The richness of ammonia oxidizers in the upper layers(40–50 cm)of the HCW and L-CW further facilitated NH_(4)^(+)–N removal.Moreover,the average total nitrogen(TN)removal efficiencies of the H-CW and L-CW were 1.99 and 1.59 times that of C-CW,respectively,owing to enhanced denitrification by MPCM.Furthermore,N2O emissions were reduced by 81.31%and 70.83%in the H-CW and L-CW,respectively.This study provides an effective approach for improving nitrogen removal and reducing N2O emissions during the treatment of secondary effluent by CWs.

Construction of hybrid constructed wetlands for phosphorus chemical industry tailwater treatment in the middle Yangtze river basin:Responses of plant growth and root-associated microbial communities

Constructed wetlands are commonly utilized to treat industrial wastewater due to their effectiveness,affordability,and environmental benefits.Many phosphorus chemical enterprises in the middle Yangtze River basin are facing high pollution load challenges and efforts are needed to improve removal efficiency of pollutants.This work was the first to use constructed wetlands for phosphorus chemical industry tailwater(PCITW)treatment.The new hybrid constructed wetlands(CWs)proposed were the aeration horizontal subsurface flow constructed wetland(AHSCW)and the integrated vertical flow constructed wetland(IVCW),which were constructed on a pilot scale.Here,the effectiveness of pollutant removal along hybrid CWs,wetland plant growth,and rootassociated microbial community responses to the PCITW were investigated.The results showed that there was spatial variation in removal of carbon,nitrogen,and phosphorus in the hybrid CWs,and that the AHSCW and the IVCW played synergistic roles in the removal of pollutants.Compared with influent,the toxic effect of effluent to embryos of a rare minnow(Gobiocypris rarus)was alleviated.Exposure to the effluent resulted in no malformation or death for embryos.Plants and microorganisms in the wetland system of the phosphate chemical tailwater were then compared with the control system of municipal tailwater.Plants in the former system had lower root density,and higher average root diameter,root shoot ratio,specific root length,and specific surface area.Plant roots also had decreased NH_(4)^(+)uptake ability but increased Ca^(2+)uptake to adapt to the high load and complex pollution stress.Unlike the control system,stochastic mechanisms had a more important role than deterministic processes in shaping the microbial community assembly associated with the PCITW.Meanwhile,analysis of microbial network-level topological characteristics demonstrated substantial reduction in network interactions complexity and microbiome stability in the treatment system.Findings from this study suggest wetlands will be helpful for efficient purification of phosphorus chemical industry wastewater in the Yangtze River basin.

Synergistic improvement of nitrogen and phosphorus removal in constructed wetlands by the addition of solid iron substrates and ferrous irons

Sanjiang Plain is intensively used for rice production,and ditch drainage diffuse pollution prevention is crucial.Groundwater,rich in Fe ions,is the main source of irrigation water in this region.In this study,pyrite and zero-valent iron(ZVI)(sponge iron and iron scraps)were used as substrates to identify the synergistic influence of exogenous Fe^(2+)addition and solid iron substrates on pollutant removal in constructed wetlands.Based on the results,iron substrates hardly improved the ammonia removal,mainly because of the physical structure and oxidation activity.At a hydraulic retention time longer than 8 h,the pollution removal efficiency in the zero-valent iron(ZVI)substrate treatment increased significantly,and the removal of nitrate(NO_(3)^(−)-N)and total phosphorus(TP)in the iron scrap substrate treatment reached about 60%and 70%,respectively.The high-throughput sequencing results showed a significant increase in the abundance of microorganisms involved in denitrification and phosphate accumulation in biofilms on ZVI substrates.The highest diversities of such microorganisms in biofilms on iron scraps were found for denitrifying bacteria(Pseudomonas),nitrate-reducing Fe(II)-oxidizing bacteria(Acidovorax),and Dechloromonas with autotrophic denitrification and phosphate accumulation,with a 43%cumulative abundance.Dechloromonas dominated in the iron sponge substrate treatment.The highest relative abundance of Acidovorax was found in the mixed iron substrate(pyrite,sponge iron,and iron scraps)treatment.The addition of ZVI substrate significantly improved the removal of NO^(3)_(−)-N and TP and reduced the hydraulic retention time through the continuous release of Fe^(2+)and the promotion of microbial growth.When designing constructed wetlands for treating paddy field drainage,the appropriate addition of iron scrap substrates is recommended to enhance the pollutant removal efficiency and shock load resistance of CWs.