Field-scale application of constructed wetlands for treating surface water contaminated by an informal settlement

Constructed Wetlands (CWs) are a cost-effective, versatile and sustainable choice for wastewater treatment. In these environments, microbial communities play a significant role in pollutant removal. However, little is known about how microbial communities in full-scale CWs contribute to maintaining water quality or how their dynamics change in response to pulse disturbances such as fire or freezes. Furthermore, few studies have examined the relationship between CW microbial community structure and performance in full-scale industrial operations. We characterized the water-column and leaf-litter layer microbial communities in a 110-acre free water surface CW that provides tertiary wastewater treatment to a plastics manufacturing plant. The CW’s sampling campaign was conducted over a 12-month period that included Winter Storm Uri, a 100-year freeze event. Analysis of 16S rRNA gene amplicon sequences revealed that the bacterial communities experienced a temporal shift. There was also a shift in microbial community structure between the influent and the first segment of the CW. However, no differences in microbial community structure were observed in the second segment of the CW. There was a negative association between microbial community diversity and chlorophyll a, as well as microbial community diversity and total suspended solids (TSS); demonstrating an increase in microbial biodiversity as water quality improved throughout the CW. Six months after the freeze, CW performance in terms of removal of water quality constituents began to return to former removal trends. Yet, there was still a significant difference in microbial community structure within the CW relative to the previous year. This suggests CW functional resilience despite a shift in microbial community structure in the wetland.

Constructed wetlands (CW) are built to improve water quality while serving as an alternative sustainable habitat for aquatic life. In Malaysia, CWs are designed according to the guideline for Urban Stormwater Management Manual for Malaysia (MSMA 2nd Edition) 2012. This study shall evaluate the performance of constructed wetland design as stipulated by MSMA through assessment of water quality and phytoplankton growth, which acts as a biodiversity indicator. A 5-month sampling period with phytoplankton abundance in a constructed wetland was correlated with the selected water quality index (WQI) parameters comprising dissolved oxygen (DO), ammoniacal oxygen (AN), chemical oxygen demand (COD), biological oxygen demand (BOD), total suspended solid (TSS), and pH. The constructed wetland consists of three main zones, namely the forebay, macrophytes and micropool zones. The highest WQI value was obtained from the micropool zone with a range of 78.98-85.45 (82.71±3.35) while the lowest WQI value was collected from the macrophytes zone with a range of 68.13-77.96 (73.25±3.42). A total of 15 phytoplankton species from 5 different algal phyla were identified in the constructed wetland. Phytoplankton distribution was high in the macrophytes zone (521 cell m-3) during dry season due to high nutrient concentration as opposed to the other zones. The phytoplankton distribution was found to be closely associated with DO, AN, TSS and total phosphorus. At the same time, the macrophyte zone design also affects the distribution of phytoplankton.

Removal of acidic pharmaceuticals by small-scale constructed wetlands using different design configurations

Water quality is declining due to the rise of urbanization, overpopulation, industrial production, climate change, non-compliance of wastewater treatment plants, and agricultural waste. The mushrooming of informal settlements along the bank of the Diep River due to population growth in Dunoon compromises the quality of water. Inadequate sanitation and waste disposal practices in the Dunoon informal settlement are a major problem, leading to the contamination of water resources. This research aimed to investigate the impact of Dunoon informal settlement on the Diep River water quality. Water samples were collected for 4 months from four sites of the river to cover the spatial distribution. The laboratory determined the concentrations of nitrates, phosphates, dissolved oxygen, chemical oxygen demand, total suspended solids, and E. coli, while the field study used a multiparameter reader to determine turbidity, temperature, electrical conductivity, pH, salinity, and dissolved oxygen. The results were compared with the South African water quality guidelines for irrigation, recreation, and aquatic ecosystems, and South African National Standards. The study revealed that the average concentrations of E. coli, dissolved oxygen, electrical conductivity, salinity, turbidity, chemical oxygen demand, and ammonia exceeded the recommended limits in both the wet and dry seasons. Based on the findings, the water quality in Diep River is poor and the Dunoon informal settlement has contributed to this to some extent. The pollution of the river may be linked to health problems and environmental degradation. Considering this, the waste discharged into the neighbouring aquatic environments needs to be monitored and managed frequently.

The research on the purification effect of artificial wetland on micro-polluted river and the detection of aquatic plants showed that TP, TN, NH3-N and COD in river were significantly lower than those in untreated river, indicating that the artificial wetland has a good purification effect on these water quality indicators; Testing from different wetland types, it can be seen that the effect of removing TP, TN, NH3-N and other factors in the subsurface wetland is the best, and the artificial surface wetland is second, while the effect of removing COD factor it is close to that of artificial surface wetland. As for the effect of removing pollution factors in artificial wetlands in different seasons, it can be drawn frow the test that the removal rate of TP and TN in artificial wetlands in different seasons can be obtained: wet season > normal season > dry season; and the removal rate of NH3-N and COD is normal season > dry season > wet season. In addition to the TN factor, the water quality during the dry season and normal season is significantly better than that during the wet season. Based on the analysis of the total amount of heavy metals absorbed by three kinds of aquatic plants, it can be concluded that different plant has different effect of removing TN and TP.

In this study, four large pilot-scale horizontal–vertical hybrid constructed wetlands (CWs) were constructed for the tertiary treatment of effluent of North Wastewater Treatment Plant in Isfahan, Iran. The plant effluent did not meet the regulation limits of wastewater reuse for various applications (e.g., irrigation of food and non-food crops, forests and green areas, groundwater recharge, and urban reuse applications). So the hybrid CW system was set up to provide a suitable effluent for this purpose. Each hybrid unit consisted of a 100-m2 horizontal flow (HF) and a 32-m2 vertical flow (VF) subsurface CW operating in series. Three emergent plants consisting of Phragmites australis, Typha latifolia, and Arundo donax were planted in the CWs and one unit left unplanted. The filling material was fine grain from 3–7 mm. The average organic load and the average hydraulic loading rate (HLR) of the system were 15 g biochemical oxygen demand (BOD5) m−1 day−1 and 5.3 cm day−1, respectively. The k-C* first-order model constant was computed for seven physical, chemical, and microbiological parameters—BOD5, chemical oxygen demand (COD), total suspended solids (TSS), NO3-N, NH4-N, total phosphorus (TP), and fecal coliforms—based on the influent/effluent concentration data for estimation of required surface area of full-scale CWs in the future. The results of 12-month sampling showed that the hybrid HF-VF CWs are highly efficient in removing of the BOD5 (85 % medium), COD (80 % medium), TSS (79 % medium), NH4-N (78 % medium), TP (74 % medium), and fecal coliforms (99 % medium). Also, there were no significant differences between various planted hybrid CWs in removal efficiency and first-order model constant for BOD5, COD, TSS, and coliforms, nor were there significant differences between planted and unplanted CWs for these parameters. But, for nutrients, the removal efficiencies of planted CWs were higher than those of control CW during the operation time. Among the CWs, the Phragmites showed the best efficiency for removal of nutrients followed by Arundo. It was observed that the removal efficiencies in HFCWs were higher than those in VFCWs due to longer hydraulic retention time (HRT), but for coliform removal, the VFCWs showed a higher efficiency. The effluent quality met the requirements for its reuse in various applications, but bacterial contents were equal to levels that permit the reuse of effluent in the non-food crop, forest and other green area irrigation, groundwater recharge, and some urban applications with restricted public exposure. The results of this pilot-scale research study showed that the performance of a single HFCW was probably not sufficient to achieve a suitable water quality for reuse of effluents and the hybrid CWs are more efficient and feasible systems for this purpose.

Macrophytes play an important role in natural and constructed wetlands (CWs). Their most important function is removal of excessive levels of some substances, such as nutrients, total suspended solids, trace elements, etc. CWs are widely used all around the world to treat many types of wastewater, with relatively high removal efficiency (5-day biochemical oxygen demand [BOD5]—around 80 %, total nutrients—approx. 40 % in the case of domestic sewage). Considering the purpose of CWs application, a few types were created with several variants in certain environmental conditions and for many effluent types with various loads of many substances. Two main types of flow through CWs are considered—surface and subsurface flow. The latter is further divided into horizontal and vertical flow. The most popular use of CWs is for domestic and municipal wastewater as secondary and tertiary treatment stages. Among macrophytes applied for phytoremediation, great diversity of plant species has been observed, especially native species and a wide range of ubiquitous species, such as Phragmites australis and Typha spp. Most macrophyte species also play an important role in natural ecosystems in improvement of surface water quality. Many species are utilized as indicators of water quality, even when low pollutant levels occur, while others are important for phytoextraction or phytostabilization.

New insights into the pollutant composition of stormwater treating wetlands

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.

Suspended solids and nutrient retention in two constructed wetlands as determined from continuous data recorded with sensors

Application of constructed wetlands in the PAH remediation of surface water: A review.

Compared to the conventional wastewater treatment plants, constructed wetlands (CWs) are low-cost and affordable green technologies for treating many types of wastewater. This study aimed to evaluate the sustainability of an old-single CW, after four years of operation, and compare its performance with a new-smaller CW, using Cyperus alternifolius plant and applying Hydraulic Retention Time (HRT) for one day. Two artificial wetlands, namely CW-B and CW-S, were used with dimensions (length x width x height) of 170 x 70 x 70cm and 71 x 42.5 x 52.5cm, respectively. The first operation of the CW-B was in September 2015 and the CW-S was in April 2019. Several concentrations of household greywater influent were loaded into the CWs to analyze their performance. Two aeration pipes were installed in the wetland system to increase the oxygen level in the systems. Water quality parameters namely Biological Oxygen Demand (BOD), Total Suspended Solid (TSS), detergent, and Dissolved Oxygen (DO) were laboratory tested before and after treatment. Research carried out during April to October 2019 resulted in the mean removal efficiencies for CW-B and CW-S being 94.13% and 96.84% for BOD; 95.04% and 95.62% for TSS; 97.11% and 94.61% for detergent; and 99.5% and 79.7% for DO increase, respectively. These findings indicate that the removal efficiencies of those parameters in both wetlands were not significantly different. Hence, the system of the old CW-B wetland still keeps a good working process. Referring to the national standards of water quality, the greywater effluents were safely discharged into water bodies and could be used for irrigation needs. A further study needs to be developed to maximize the detergent removal to meet the existing standard for hygiene sanitation. These results suggest that CWs are becoming a sustainable solution for the treatment of greywater at the household level and finally contributing to minimizing the pollution of water.

Constructed wetlands (CWs) are important plant filters used for wastewater treatment. The behavior of the Canna indica-planted CWs in the face of a highly variable composition of industrial wastewater has yet to be understood. Here, we show the effectiveness of Canna indica-planted and unplanted vertical subsurface flow CWs for the treatment of Algiers petroleum refinery’s effluent. The selected species was placed in the CWs containing light expanded clay aggregate (LECA) and sand as a substrate. The findings indicate that the planted constructed wetlands efficiently removed 85% of total suspended solids (TSS), 96.38% of total nitrogen (TN), 96.15% of nitrate nitrogen (NO3−-N), 99.15% of ammonium nitrogen (NH4+-N), and 99.87% of nitrite nitrogen (NO2−-N). The overall mean removal efficiencies for heavy metals in the vegetated CWs were considerably greater than those of the control. Concentrations of Cr, Cu, Fe, Pb, Zn, Al, Ni, and Cd were calculated in the roots, rhizomes, leaves, and stems of the plant; then, the bioaccumulation factor (BAF) and translocation factor (TF) were determined. An initial examination using scanning electron microscopy (SEM–EDX) was also included in the study. The analysis indicated that toxic elements were adsorbed on plant tissues, concentrated in the roots, and partially transported to the aerial parts. These results are useful for the design of CWs to treat industrial wastewater, enabling water of acceptable quality to be discharged into the environment, especially as a low maintenance and cost-effective technology in developing countries.

A review on performance of constructed wetlands in tropical and cold climate: Insights of mechanism, role of influencing factors, and system modification in low temperature

This paper reports a study on the performance of a multistage constructed wetland (CW) system adopted for winery wastewater and on the analysis of its suitability for irrigation reuse. The CW system treats about 3 m3·day−1 of wastewater produced by a small winery located in Sicily (insular Italy). Wastewater samples were collected at the CW inlet and outlet for physical–chemical and microbiological quality characterization. CW efficiency was evaluated on the basis of water quality improvement and of the achievement of Italian and EU irrigation reuse regulation limits. The CW system showed Chemical Oxygen Demand (COD) and Total Suspended Solids (TSS) mean removal rates of about 81% and 69%, and a maximum removal of about 99% (for both COD and TSS) occurred during grape harvest phase. The CW removal efficiencies for nutrients were 56% for TN and 38% for PO4-P, considering their low average concentrations at CW inlet. The CW system evidenced an effluent average quality compatible with the limits imposed by the Italian regulation and EU proposal regulation on the minimum requirement for water reuse. The CW vegetated area showed regular growth and vegetative development; phytotoxicity phenomena were not detected. The results of the study suggest the important role of CW systems in the treatment of winery wastewater and for their subsequent reuse in agriculture.