Wetland Wastewater Treatment System Research Articles

Bioenergy-producing two-stage septic tank and floating wetland for onsite wastewater treatment: Circuit connection and external aeration

This study designed a two-stage, electrode-integrated septic tank-floating wetland system and assessed their pollutant removal performances under variable operational conditions. The two-stage system achieved mean organic, nitrogen, phosphorus, and coliform removal percentages of 99, 78, 99, and 97%, respectively, throughout the experimental run. The mean metals (chromium, cadmium, nickel, copper, zinc, lead, iron, and manganese) removal percentages ranged between 81 and 98%. Accumulated sludge, filler media, and the hanging root mass contributed to pollutant removals by supporting physicochemical and biological pathways. The mean effluent organic concentration and coliform number across the two-stage system were 20 mg/L and 1682 CFU/100 mL, respectively, during the closed-circuit protocol, which was beneath the open-circuit-based performance profiles, i.e., 32 mg/L and 2860 CFU/100 mL, respectively. Effluent organic, nitrogen, phosphorus, metals, and coliform number ranges across the two-stage system were 9–17 mg/L, 13–24 mg/L, 1–1.5 mg/L, 0.001–0.2 mg/L, and 1410–2270 CFU/100 mL, respectively during intermittent and continuous aeration periods. The air supply rate differences influenced pollutant removal depending on the associated removal mechanisms. The non-aeration phase produced higher effluent pollutant concentrations than the aeration periods-based profiles. The overall mean power density production of the septic tank ranged between 107 and 596 mW/m3; 110 and 355 mW/m3 with the floating wetland. The bioenergy production capacity of the septic tank was positively correlated to external air supply rates. This study demonstrates the potential application of the novel bioenergy-producing septic tank-floating wetland system for wastewater treatment in decentralized areas.

Performance evaluation of a pilot wetland system for wastewater treatment

Wetland systems are inexpensive and easy-to-operate wastewater systems and are widely used globally at different scales for the safe treatment of wastewater. This study aims to evaluate a pilot-scale vertical flow wetland system treating wastewater under different loadings. The wetland system was constructed using indigenous plants (Imperata cylindrical) and operated using actual wastewater for twelve-months. Samples from influent and effluent of the wetland system were collected weekly. They were analyzed for parameters listed in the Kuwait Environment Public Authority standards for reuse in irrigation, such as organic matter, nutrients, heavy metals, and microorganisms. The results showed that the high hydraulic loading rate (1.67 m3/m2.d) phase was more efficient than the low hydraulic loading rate (1.04 m3/m2.d) phase in terms of organics and nutrient removal efficiency. The range of the removal efficiency of organic matter in low and high loading rates was around 48.5–49.0% and 59.1–59.1%, respectively. In addition, the range of the removal efficiency of nutrients in low and high loading rates was around 43.7–67.7% and 24.7–76.6%, respectively. Moreover, the range of the removal efficiency of heavy metals under the low and high loading rates was − 134.3–93.8% and − 1545.7–92.6%, respectively. It was evident that he metals were leaching from the soil. Moreover, it was found that the system performance was closely linked to the ambient temperature effects during the start-up (r = 0.59) and high hydraulic loading (r = 0.43) phases for example. While ambient temperature has wider effects on wetland biota, its effects on the plants are more pronounced. In conclusion, wetland systems can be constructed using indigenous plants to treat office wastewater efficiently under the harsh climate conditions of Kuwait with adjustments in capacity, loading rates, and operational conditions.

Comparing the potential treatment of biogas effluent by two artificial wetland wastewater treatment systems

Comparing the potential treatment of biogas effluent by two artificial wetland wastewater treatment systems

Phytoextraction and nutritional quality of forages cultivated in a constructed wetland system for wastewater treatment

This study aimed to evaluate the effects of different concentrations of sodium on the phytoextraction of nutrients and nutritional quality of forages (P. purpureum Schum and C. dactylon Pers) grown in wetland system constructed for wastewater generated in cattle slaughterhouses (WGCS) treatment. The experiment was conducted in a randomized complete block design with three replications. The treatments were tested using 2 x 5 factorial scheme, as follows: two species of grass (P. purpureum Schum and C. dactylon Pers) and five concentrations of sodium in WGCS: 70, 100, 150, 200 and 250 mg L-1. The phytoextraction potential of nutrients and the nutritional quality of forages grown in pots simulating a wetland system constructed for WGCS with sodium concentrations were assessed in terms of the contents of the nutrients nitrogen, phosphorus, potassium, calcium, magnesium and sodium in leaf tissues. The accumulations of these nutrients in the produced forages were also evaluated. Both species presented different behaviors regarding their nutrient phytoextraction potentials. The nutritional quality was changed in the forages due to the cultivation in constructed wetlands. Forage C. dactylon Pers presented higher phytoextraction potential of sodium and potassium and P. purpureum Schum presented a higher nutritional quality.

Integrated Anaerobic-Aerobic and Wetland System for Wastewater Treatment and Recycling in Fish Canning Industry

Fish canning industry is one of the top priority industries in Indonesia that is competitive in international market and essential to food security. It is also an industry with high water consumption due to its water-intensive processes such as thawing and washing that produces large amount of wastewater containing very high load of organic pollutants which must be treated properly before disposal into the environment. This study was conducted using wastewater characteristics from one of the fish canning plants in Bali, Indonesia, that already implemented wastewater treatment using a combination of aerobic treatments with trickling filter and activated sludge. The treatment system has difficulty to achieve a good and stable effluent quality, especially during high load production season. It is necessary to find a better system that can treat the high load of organic content in wastewater and produce a cleaner effluent that can be recycled back into the production process. This study is aimed to develop a model of integrated system comprised of sedimentation, coagulation-flocculation, Upflow Anaerobic Sludge Blanket (UASB) and Modified Ludzack-Ettinger (MLE) that can be used as a base design for further implementation in pilot-scale facility. The integrated system was designed to remove 99 % of BOD, 99 % of oil and grease, 98 % of TSS and 87.8 % of total nitrogen achieving effluent quality of 59.9 mg/L BOD, 0.6 mg/L oil and grease, 27.4 mg/L TSS, and 30.0 mg/L total nitrogen in nitrates form. Compared to the existing treatment system with effluent quality of 351.4 mg/L BOD, 337 mg/L TSS and 111.1 mg/L ammonia, this system could improve the effluent quality significantly by maintaining a hydraulic retention time (HRT) of 55.3 h. Combining constructed wetland with HRT of 28.8 h as water reclamation system to refine the water quality, the nitrogen content could be reduced to less than 10 mg/L to meet the requirement as raw water for clean water production process. The design in this study could be used to replace the existing aerobic treatment system and enable the industry to solve the environmental problems of wastewater disposal and water conservation and expand further the production capacity simultaneously.

The potential of anaerobic-constructed wetland system for wastewater treatment of rice straw pulping

Wastewater of cooking rice straw in the manufacture of pulp contains high levels of pollutants that must be treated first before being discharged into the environment. The purpose of this research is to study the potential of anaerobic and constructed wetland systems in treating pulp-making wastewater from rice straws. Anaerobic reactor with a volume of 30 L was filled with 5 L domestic sludge as sludge seed. Wastewater with COD of 762 - 17,900 mg/L, BOD5 of 354 – 8,000 mg/L, and TSS of 123 - 350 mg/L was fed into the anaerobic reactor. The organic loading rate was varied from 0.15 to 2.13 kg COD/m3 day, during the residence of wastewater for 5-8 days. Anaerobic reactor effluent was further processed in a constructed wetland reactor that varies in height from a mixture of sandy soil of 10-30 cm. The hydraulic residence time of wastewater in the constructed wetland reactor was 6.7 - 11.6 days. Influent and effluent of anaerobic and constructed wetland reactors were analysed for COD, BOD5, TSS, and pH parameters. The result indicated that wastewater treatment with anaerobic system could reduce COD of 63-72% and BOD5 of 65-75%, and the constructed wetland system could reduce COD and BOD5 of 96.5% and 96.1%, respectively.

Influence of Phragmites communis and Zizania aquatica on rhizosphere soil enzyme activity and bacterial community structure in a surface flow constructed wetland treating secondary domestic effluent in China.

The present study aims to investigate the effects of Phragmites communis and Zizania aquatica on rhizosphere soil enzyme activity and bacterial community structure in a surface flow constructed wetland (SFCW) for the treatment of domestic sewage from the Shanxi province of China. The basic physical and chemical properties of the soil, the contents of soil urease (UE), alkaline phosphatase (ALP), soil microbial biomass carbon and nitrogen (SMBC, SMBN), and bacterial community structure were measured in the Phragmites communis group (PG), Zizania aquatica group (ZG), and control group (CG), respectively. The results showed that (1) the contents of UE, ALP, SMBC, and SMBN in rhizosphere soil of PG were more than those of ZG; (2) the highest bacterial abundance and α-diversity appeared in PG, in which Gp6 was the most abundant bacterial genus in PG; (3) the main functions of the dominant bacteria Gp6 and Longilinea in PG were involved in metabolizing multiple carbohydrates and participating in the carbon cycle in the soil based on the clusters of orthologous groups pathway analysis data; (4) the bacterial community of PG was mainly affected by the positive correlation with arsenic, nickel, or SMBC via the redundancy analysis. Collectively, Phragmites communis is a recommended species for wastewater wetland treatment system in Shanxi province, and the special enzymes and dominant bacteria in plant rhizosphere soil had obvious functions of removing organic pollutants. Besides, the influences of environmental factors on rhizosphere bacteria and the combined effects of Phragmites communis and dominant bacteria in wetland wastewater treatment system should be taken seriously.

Research on perfermance improvement of constructed wetland wastewater treatment system

Constructed wetland is a kind of wastewater ecological treatment technology. It has the advantages of low investment, convenient operation and management, stable water quality, and has certain landscape effects. Therefore, it is widely used in the field of wastewater treatment. However, this technology still has certain problems in practical engineering applications, such as irregular design and clogging, resulting in limited service life and processing performance of the wetland. The type selection of constructed wetlands, matrix type and particle size, plant type and configuration, and water inflow mode and operating parameters are the main factors affecting the operating life and purification effect of constructed wetlands. Based on the author’s practice, the article introduces in detail the current process structure, basic design methods and economic and technical comparison of constructed wetland wastewater treatment for reference by relevant scientific research and design units.

Effective Purification in Constructed Wetlands Using Strontium-Doped TiO2 Coated on Porous Ceramic Filter Media

This research is the first report on the purification of domestic wastewater in respect to the application of strontium-doped TiO2 coated on porous ceramic filter media (Sr-TiO2/PCFM) in eight laboratory-scale vertical flow constructed wetlands under irradiation of UV light. All the major pollutant parameters of wastewater were investigated. The online parameters showed that the decrease of dissolved oxygen (DO) reached 68.89% and in the constructed wetlands group which had the Sr-TiO2/PCFM material and had a certain anti-clogging ability. By the presence of photocatalyst Sr-TiO2/PCFM material, the removal efficiency of COD reached over 80% and eventually stabilized at a higher level (over 71%). Besides that, the Sr-TiO2/PCFM material in constructed wetlands improved the average removal efficiency of total phosphorus (TP), total nitrogen (TN), NH4+-N, total suspended solids (TSS), and turbidity by 60.89%, 34.89%, 41.87%, 21.10%, and 36.85%, respectively. With Sr-TiO2/PCFM material, under the irradiation of UV light, the overall removal efficiency of organic matter removal in terms of dissolved organic carbon (DOC) was 52% in 4 h, which was the best compared with other constructed wetland groups. The results of this study may in turn support improved testing and better optimization of constructed wetland systems for wastewater treatment.

Efficiency of two constructed wetland systems for wastewater treatment: removal of bacterial indicators and enteric viruses

AbstractBACKGROUNDPathogenic microorganisms at the effluents of treatment plants entail a potential risk to public health. Enteric viruses such as adenoviruses (AdVs) and enteroviruses (EVs) are responsible for many waterborne diseases. Wastewater treatment methods eliminate successfully the load of indicators but other pathogens such as viruses have been detected in high concentrations at the effluents of wastewater plants. In this perspective, two constructed wetlands (CWs) systems (S1 and S2) were employed and fed with primary wastewater. S1 consists of a free water surface (FWS) wetland and a horizontal subsurface flow (HSSF) wetland working in series, while S2 consists only of the HSSF. Also, both systems included a sand filter (SF) after the HSSF.RESULTSResults showed that these low‐cost systems are capable of eliminating effectively the bacterial indictors (total coliforms, Escherichia coli, Enterococci) achieving removal rates of almost 99% for S1 (3.2–4 Log units) and 89–98% for S2 (1.9–2.7 Log units). Regarding viruses, AdVs, EVs and phages were detected at all sampling points and during all seasons, and they were only partly removed in S1 and/or S2. For example, the virus load was decreased by 2.5 Log units for AdVs and 3.4 Log units for EVs in the case of S1, while the respective values were 4.3 and 1.9 Log units for S2.CONCLUSIONSGenerally, CWs eliminated successfully the bacterial load, while the remaining virus load was significant, thus strengthening the argument that viruses could be a reliable indicator for fecal contamination. © 2019 Society of Chemical Industry

Phytoremediation performance of Lemna communities in a constructed wetland system for wastewater treatment

Duckweeds are considered suitable plants for bioremediation of wastewaters because they can tolerate and take up diverse pollutants and large quantities of nutrients. They have year-round vegetative growth that can reach very high rates using wastewater nutrients that can accumulate intracellularly or be utilized to produce new biomass. The constructed wetland that services the town of Forano (Central Italy) is composed of three interconnected, but distinct, treatment pools (P1, P2, P3). In this study the phytoremediation performance of the whole treatment system was assessed taking into consideration pH, temperature, oxygen, nitrates, phosphates, sulphates, and pathogenic bacteria (Escherichia coli) at the inlet and outlet of each pool once per season over a year. The remediation efficiency of P2 was lower than in P1 and P3, and this was shown to be due to an extended, dense free-floating Lemna mat. The mat was thick enough (18–30 mm) to block light penetration, and heat and gas exchange to the underlying water resulting in dark, cool and near-anaerobic conditions. These conditions limited aerobic biodecomposition processes and natural control of the E. coli population. The underlying fronds of the Lemna mat in P2 were highly necrotic and became a source of nutrients, shown by an increase in nitrates and phosphates from the inlet to the outlet. Lemna use in phytoremediation is often considered highly important, but it is shown here that active management interventions are required and should involve periodic harvesting of Lemna fronds to avoid mat over-development and formation of necromass.

Life cycle assessment of constructed wetland systems for wastewater treatment coupled with microbial fuel cells.

The aim of this study was to assess the environmental impact of microbial fuel cells (MFCs) implemented in constructed wetlands (CWs). To this aim a life cycle assessment (LCA) was carried out comparing three scenarios: 1) a conventional CW system (without MFC implementation); 2) a CW system coupled with a gravel-based anode MFC, and 3) a CW system coupled with a graphite-based anode MFC. All systems served a population equivalent of 1500 p.e. They were designed to meet the same effluent quality. Since MFCs implemented in CWs improve treatment efficiency, the CWs coupled with MFCs had lower specific area requirement compared to the conventional CW system. The functional unit was 1m3 of wastewater. The LCA was performed with the software SimaPro® 8, using the CML-IA baseline method. The three scenarios considered showed similar environmental performance in all the categories considered, with the exception of Abiotic Depletion Potential. In this impact category, the potential environmental impact of the CW system coupled with a gravel-based anode MFC was around 2 times higher than that generated by the conventional CW system and the CW system coupled with a graphite-based anode MFC. It was attributed to the large amount of less environmentally friendly materials (e.g. metals, graphite) for MFCs implementation, especially in the case of gravel-based anode MFCs. Therefore, the CW system coupled with graphite-based anode MFC appeared as the most environmentally friendly solution which can replace conventional CWs reducing system footprint by up to 20%. An economic assessment showed that this system was around 1.5 times more expensive than the conventional CW system.

Performance comparison of plant root biofilm, gravel attached biofilm and planktonic microbial populations, in phenol removal within a constructed wetland wastewater treatment system

This study was performed in order to understand the relative contribution of a constructed wetland (CW) system's various components to phenol degradation (100 mg∙L-1) under controlled plant biomass/gravel/ water experimental ratios. This was done by division of a pilot-scale CW system into its components, with or without their associated bacteria: (i) gravel, plant and water; (ii) gravel and water; (iii) water; (iv) gravel; (v) plant; (vi) control (sterile water). The highest phenol biodegradation rate occurred for the gravel-attached biofilm followed by root-attached biofilm and planktonic population, which recorded a similar rate to each other and a much lower rate than the gravel-attached biofilm. A control containing CW planktonic inactivated bacteria (autoclaved water) did not impact phenol removal, revealing that microbial populations are the major factor in phenol removal. The differences in the phenol removal achieved could be attributed to higher numbers of specific phenol degraders on the gravel surface, compared to lower numbers of root-attached and planktonic bacterial fractions, as isolated using phenol-agar plates which contained phenol as the sole carbon source. The main contributor to our findings appears to be the larger surface area provided by the gravel bed compared to plant roots.

Feasibility, Design Criteria, and O&M Requirements for Small Scale Constructed Wetland Wastewater Treatment Systems

The expanding use of decentralized wastewater management has resulted in an increased interest in small-scale wetland treatment systems. However, there is limited information available on the use, distribution of and performance of these small-scale systems. The purpose of this study was to address this knowledge gap by developing criteria for the feasibility, design, operation, and maintenance of small-scale wetland treatment systems. Information on 1,789 existing small-scale wetland treatment systems in 19 countries was collected. Monitoring data from the assembled small-scale wetland database was used to develop sizing criteria for FWS and VSB wetlands. Loading rates and corresponding effluent quality were developed for BOD, TSS, TKN, phosphorus, and fecal coliform bacteria. Where there was adequate data, the variation in monthly vs. annual average effluent concentration was assessed to provide a factor-of-safety approach to wetland sizing. Information on internal processes, hydraulic design, operation, maintenance, cost, and industrial applications of constructed wetlands is also presented in this report. This title belongs to WERF Research Report Series ISBN: 9781843397281 (Print) ISBN: 9781780403991 (eBook)

Wetland Wastewater Treatment System for Small City Suburbs – A Review

This paper deals with a conceptual idea of integrating natural wetlands into the infrastructure of a city or community for treatment of wastewaters that are generated. The paper deals with constructed wetlands and their role in treatment of wastewater. Following which the idea of how or rather why not can a natural wetland be integrated into the treatment infrastructure is discussed citing the various challenges that may come up when trying to put into action such a system and certain possible solutions that can be tried. This still being at the concept stage, lots more research into the finer details need to be done before such a concept can actually materialize.

Embodied water accounting and renewability assessment for ecological wastewater treatment

For water accounting of wastewater treatment, existing studies focused on either direct water loss caused by evaporation/evapotranspiration by natural process or indirect water cost induced by economic inputs. As an extension of our previous work (Shao and Chen, 2013), both the direct and indirect water losses as embodied water are accounted for in the present study. A set of improved indicators have also been devised to assess the efficiency and renewability of wastewater treatment. After accounting and analyzing the embodied water of a pilot constructed wetland wastewater treatment system as an ecological engineering in Beijing, a comparison has been carried out between the case system and a traditional wastewater treatment plant based on the proposed indicators. The traditional wastewater treatment technology is illustrated however superior to the ecological way in terms of water use context. The present framework is capable of providing clear guidance for prioritizing options of wastewater treatment technologies by evaluating water trade-off, beyond the usual practice on treatment efficiencies and quality standards in effluents.

Exergy based renewability assessment: Case study to ecological wastewater treatment

The renewability assessment has seldom been a core issue in previous studies. This work presents a framework to assess the renewability of a production system based on the unified ecological evaluation method of embodied cosmic exergy analysis. For the first time, both historical renewable and nonrenewable resources uses of each social product input of a system are individually and completely traced and measured by the embodied cosmic exergy as available energy. A set of indicators have also been devised to assess the resources utilization efficiency and renewability of a production system. To demonstrate the framework, a case study is carried out for a pilot constructed wetland wastewater treatment system in Beijing. The resources utilization style and renewability of the case system are analyzed and assessed. The presented framework can be easily transplanted to assess the renewability of other products, which could contribute a lot to meet the goal of sustainable development.

Mechanisms of Phosphorus Removal in a Pilot-Scale Constructed Wetland/BOF Slag Wastewater Treatment System

Abstract Removal of PO4-P, NH3-N, cBOD5, chemical oxygen demand (COD), Escherichia coli, and total coliforms in a pilot-scale hybrid constructed wetland (CW) wastewater treatment system was evaluated. Wastewater was sequentially passed through a mixing cell, an aerobic treatment cell, a P treatment cell that contained basic oxygen furnace slag (BOFS), and an anaerobic treatment cell. The system operated for 8 months at an average flow rate of 68 L/day. Mean influent concentrations of PO4-P, NH3-N, cBOD5, and COD were 7, 25, 27, and 60 mg/L, respectively, and mean influent levels of E. coli and total coliforms were 104 and 105 CFU 100 mL−1. Effluent from the system had 95–99% lower concentrations of PO4-P, NH3-N, cBOD5, E. coli, and total coliforms, and a 72% lower concentration of COD, compared to influent values. Backscatter scanning electron imaging coupled with energy dispersive X-ray (EDX) spectra and elemental maps, along with Fourier transform infrared (FTIR) spectra, showed that P was present on th...

Laboratory Research of Distributed Domestic Sewage by Constructed Wetland Treatment Process

In order to solve practical problems of rural sewage treatment, constructed wetland waste water treatment system is chose to simulate, analyze and evaluate in laboratory. Sand and gravel, granular activated carbons were used as the filter media in the constructed wetland. Experimental results show that the removal rate of filter for the water treatment increases with the rise of the hydraulic retention time and the rise of the temperature. It can be satisfied with the treatment effect at an ambient temperature of 15°C, maintained for 4 days or more hydraulic retention time.

Plants of Constructed Wetland Wastewater Treatment Systems: A Comparison of the Oxygen Release from Roots of Typha and Phragmite

Constructed wetlands have recently been widely used around the world to purify wastewater. As an important component of constructed wetland system, plants improve water quality by increasing oxygen concentrations in the rhizosphere. However, little was known about the ability of oxygen release from roots with different species. And the reason of the difference is still unclear. This paper investigated the variation of oxygen release rate from roots ofTyphaandphragmiteusing a titanium (Ш) citrate buffer. Compared the ability of oxygen release fromTyphaandphragmite. The results shows that oxygen release rates with the same condition were higher forPhragmites. This difference is caused by the special structure ofPhragmites. The aerenchyma ofPhragmitesis good at the oxygen transport. The results of this paper can help us to choose better vegetation species for wastewater treatment.