ARTIFICIAL CONSTRUCTED WETLANDS A NOVEL IDEA FOR WASTEWATER TREATMENT TO ATTAIN SUSTAINABLE ENVIRONMENT

Sudarsan J.S^1*, Annadurai R², Deepika Venugopalan³, Rahul Singh³ and Rajitha Rajan⁴

¹Assistant Professor, Department of Civil Engineering, SRM University, India

²Professor, Department of Civil Engineering, SRM University, India

³B-Tech Undergraduate Students, Department of Civil Engineering, SRM University, India

⁴M.Tech Environmental, post graduate student, Department of Civil Engineering, SRM University, SRM Nagar, Kattankulathur, Kancheepuram District, Tamilnadu, India

*Corresponding Author:

Sudarsan J.S
E-mail: sudarsanjss@ktr.srmuniv.ac.in

Received 17 June, 2017; Accepted 24 November, 2017

Visit for more related articles at Journal of Industrial Pollution Control

Abstract

Quality of waste water. Treatment of domestic wastewater from both rural and urban areas pose to be one of the greatest challenges that the government and municipal body incur, in terms of machinery and expenditure. An alternate solution to a cleaner, greener and cost effective method for wastewater treatment is by using a constructed wetland technique. Wetland plants were grown in the lab scale wetland units. The treatment of domestic wastewater was carried out with different detention time periods such as 24 hrs, 48 hrs, and 72 hrs using Phragmites as vegetation with MBBR (Moving Bed Biofilm Reactor) as a part of treatment cell filter media for the lab scale wetland unit. The wetland units developed, consisted of a PVC tub of 70 × 40 × 30 cm and the system was built with a slight slope (<1%) between inlet and outlet zones. The treatment efficiency of the constructed wetland was observed for various parameters like Biological oxygen demand (BOD), Chemical Oxygen Demand (COD), Total Nitrogen (TN) and Total Phosphate (TP). The performance was monitored with different trials and in all the trials the reduction efficiency was found to be more effective. This kind of green initiative of eco-friendly wastewater treatment is found to be future alternative in developing countries and also it is quite economical if the land cost is less in the rural areas.

Keywords

Constructed wetlands, Moving Bed Biofilm Reactor (MBBR), Domestic wastewater, Organic pollutants, Wetland plants

Introduction

The major environmental pollution is caused by improper disposal wastewater, due to the outflow of effluents from various areas of domestic and industrial sources. Water resource is getting polluted on a large scale by disposal of untreated wastewater into nearby water source which leads to water pollution. The discharge of untreated waste water to the water bodies without any treatment processes will lead to numerous environmental problems such as:

1. Untreated Waste Water which contains a large amount of organic matter, will consume the dissolved oxygen for satisfying the BOD of waste water and thus, deplete the DO of the water stream required by the aquatic life.

2. Untreated waste water usually contains a large amount of pathogenic or disease causing micro-organisms and toxic compounds, that can dwell in the human intestinal tract thus threatening the human health.

3. Waste water may also contain certain amount of nutrients, which can stimulate the growth of aquatic plants and algal blooms thus, leading eutrophication of the lakes and streams.

4. The decomposition of the organic compounds present in waste water can lead to the production of large quantities of malodorous gases (APHA, 2005; Ashutosh, et al., 2012; Aslam, et al., 2007).

Water pollution also interferes with the growth of organisms living in the water bodies, thus retarding the natural purification process caused by such organisms. Water demand changes due to a few reasons. Increasing of population and migration to drought prone region. Industrial growth and higher per capita demand of water. Climate variations that result in change of weather patterns to name a few (Mustafa and Scholz, 2010; Baskar and Deeptha, 2009; Chan and Tsang, 2007).

Domestic wastewater was mainly composed of organic matters, nutrients and suspended solids. In the treatment process of domestic wastewater, the removals of organic matters and nutrients are critical to judge the performance of the treatment process. Most wastewater treatment systems in rural areas with low dense population are characterized by low capital investment and operating cost. Common domestic wastewater treatment methods in rural areas capitalize on microbial degradation. They include waste stabilization pond, wastewater storage and treatment reservoir, up flow anaerobic sludge blanket reactor, bio filter, aerated lagoon, oxidation ditch and constructed wetland (Decho, 2000; Design Manual Constructed Wetlands and Aquatic Plant Systems for Municipal Water Treatment, 1998).

Some of the suitable wastewater treatment processes for domestic wastewater include biological treatment processes, such as activated sludge, trickling filter, and rotating biological contractor systems. However, these treatment systems are economically feasible. Also, the treated wastewater from these types of wastewater treatment plants might require further treatment with a tertiary treatment process, such as a polishing pond, oxidation pond, or constructed wetland (CW), to improve the treated wastewater quality (Dhote, et al., 2012; Fraser, et al., 2004; Gauss, 2008).

Constructed wetlands for wastewater treatment are manmade wetlands that take advantage of the same principle as a natural wetland system but in a more controlled environment. This technology is the most commonly applied ecological treatment of wastewater (Healy and Rodgers, 2006; Vymazala and Kropfelovaa, 2008; Mant, et al., 2006). The constructed wetland system (CWS) for waste water treatment uses the facility of systems that are constructed and designed to utilize natural processes (Nicolella, et al., 2000).

There are two types of constructed wetlands:

1. Sub-surface constructed wetland.

2. Free water surface constructed wetland.

Sub-surface constructed wetlands are of horizontal or vertical flow. In horizontal flow constructed wetland, water passes horizontally through the substrate. In vertical flow constructed wetlands water is passed intermittently onto surface of sand and gravel filters and gradually drains to the filter media before being passed into the drain at the base. In free water surface constructed wetland, water flows as a shallow layer over the soil substrate (Paul, et al., 2005; Pearce, 2008; Rizzo, et al., 2013; Srinivasan and Richard, 2000; Sudarsan, et al., 2014). There is another type of constructed wetland namely vegetated submerged bed constructed wetland (VSB). VSB constructed wetland consist of gravel and soil bed planted along with vegetation (Sirianuntapiboon and Kongchum, 2006).

Horizontal sub-surface flow CW's

Horizontal subsurface flow constructed wetlands are designed so that water flows horizontally below ground surface through the substrate. The substrate provides surface area for bacterial biofilm growth. The advantages of HSSF CW's include increased treatment efficiencies, fewer pest problems and nuisance, increased accessibility for maintenance. Compared to surface flow systems, subsurface flow wetlands are also better suited for cold weather climates. Water and wastewater treatment facilities for metropolitan areas are mainly 'concrete and steel' constructions leading to high treatment costs for conventional treatment processes. Semi-urban and rural areas cannot afford such high costs and therefore they normally just dump or get minimal treatment leading to pollution of surface and groundwater bodies. It is a cheaper technique to go in for wastewater treatment (Deeptha, et al., 2015; Zhang, et al., 2010).

Materials and Methodology

From the (Figure 1) the methodology adopted for treating the wastewater was discussed.

Figure 1: Flow chart for methodology.

Study area

This study was carried out in SRM University, located in SRM Nagar of potheri village (12º 9′ N to 12º 49′ N and 80º 2′ E to 80º 3′ E), in Kancheepuram district, Tamil Nadu, India. This area experienced maximum temperature of 40ºC and minimum temperature of 20ºC with calm wind speed and average annual precipitation of 1330 mm. The university is located along NH 45, about 40 KM away from Chennai city. The mean sea level of 45m above sea level .

Construction of constructed wetland pilot scale unit

There are two horizontal subsurface flow constructed wetland is designed.

Inlet zone

In the 20 litre plastic container was used to provide a continuous flow of wastewater through the inlet. In that Shallow, rectangular basins with a high length to width ratio are usually designed for aquatic treatment systems to reduce the potential for short circuiting and to simplify harvesting operations. The use of baffles and influent distribution manifolds helps to maximize the retention time. Influent manifolds and multiple inlets (step feed) systems can also be used effectively for recycling treated effluent to reduce the influent concentrations of wastewater constituents. It is recommended that coarse gravel be placed in the inlet areas of the constructed wetland to enhance flow distribution.

Wetland cell

The pilot scale constructed wetland unit was a PVC container of length, width and depth of 70 cm, 40 cm, and 30 cm, respectively. It placed with slope 1% between inlet and outlet zones. The gravel with the size of 10-15 mm was put into the inlet and outlet zones in each cell in order to produce a uniform distributed flow. Then the remaining area of three cells was filled with sand, fine gravel and soil for normal setup. The fine gravel is replaced by Moving Bed Bio-Reactor (MBBR) media for integrated setup.

Filter media

The filter media consist of a sand bed underlain by a permeable layer. The bed was filled to a height of 7 cm with sand followed by a 7 cm with gravel of diameter 10-30 cm. Its top most layers with native soil of plant were filled to support vegetation.

Vegetation

Common Reed (Phragmites australis) are local wetland species, was used in this study. The plants were collected from a nearby lake and planted in the constructed wetland unit. The major benefit of plants is the transferring of oxygen to the root zone.

Outlet zone

The outlet zone is filled with coarse gravel placed in the outlet of the constructed wetland to enhance effluent collection. It also consists of drainage pipe laid at the bottom of the setup. The setup by setup construction of prototype model is shown in the (Figure 2a-2f).

Figure 2 (a-f): Lab scale constructed wetland with (MBBR) media

Method of collection of sample

Domestic wastewa`organic parameters as per APHA 21^st edition guidelines.

Results and Discussion

The wastewater samples were analyzed in accordance to APHA 21^st edition. The samples were studied for various parameters and the reduction percentages were noted down in Table 1. The variation of the various parameters with respect to time are plotted in the Graphs shown below. The analysis was carried out for the three types of wastewater and similar reduction percentages for the various parameters were observed.

Table 1: Reduction percentage.

Wastewater analysis

The wastewater analysis was done for different trails for the parameters BOD, COD, Total nitrogen, total phosphate as discussed in the (Figure 3a and 3b) and the overall reduction of all the parameters was discussed in (Figure 3c). It highlights that maximum reduction was achieved with BOD, COD and total nitrogen.

Figure 3a: BOD reduction with reference to time.

Figure 3b: Nitrogen reduction with reference to time.

Figure 3c: Overall % removal efficiency of COD, BOD, TN and TP.

From (Figure 3c) it was clear that organic removal efficiency was better. This may be due to the role of membrane bioreactor, which is a part of the wetland treatment cell., reduction percentage is found to be less due to the influence of clay, silt and other compounds presented in the wetland filter media and the reduction efficiency of nitrogen found to be more due to nitrification and denitrification action taking place in the wetland treatment process. As the phosphate treatment efficiency was very low in the wetland cell compare to the other parameters this may be due to the small lab scale unit was used in the trial and also the amount of vegetation in the wetland unit found to be minimum as it is a small lab scale unit.

Conclusion

Constructed wetlands with horizontal sub-surface flow have successfully been used for treatment of domestic wastewater. The concentrations of parameters COD, BOD, N and PO₄ in the influent of wastewater from sewage treatment plant in SRM University were studied with artificial constructed wetland setup. This system could achieve desirable removal efficiencies of BOD, COD, TN and TP for integrated setup as 95%, 75%, 45% and 18% respectively. The highest removal efficiencies for COD were achieved in systems treating domestic wastewater.

Acknowledgements

The authors are thankful to SRM University management and the Head of the department of civil engineering for their continuous support and encouragement in executing this research work.

References

1. APHA. (2005). Manual standard methods for the examination of water and wastewater 21st edition. AWWA, WPCF, Washington, D.C., U.S.A.
2. Ashutosh, D., Deeptha, T. and Sudarsan, N. (2012). Phytoremediation of dairy waste water using constructed wetland. International Journal of Pharma and Bio Sciences. 3 : 745-755.
3. Aslam, M.M., Malik, M., Baig, M.A, Qazi, I.A. and Iqbal, J. (2007). Treatment performances of compost based and gravel based vertical flow wetlands operated identically for refinery wastewater treatment in Pakistan. Ecol. Eng. 30 : 34-42.
4. Baskar, G. and Deeptha, V.T. (2009). Treatment of wastewater from kitchen in an institution hostel mess using constructed wetland. International Journal of Recent Trends in Engineering. 1 : 54-58.
5. Chan, S.Y. and Tsang, Y.F. (2007). Domestic wastewater treatment using batch-fed constructed wetland and predictive model development for NH3-N removal. Process Biochemistry. 43 : 297-305.
6. Decho, A.W. (2000). Microbial bio-films in intertidal systems: An overview. Cont. Shelf Res. 20 : 1257-1273.
7. Deeptha, V.T., Baskar, G. and Sudarsan, J.S. (2015). Performance and cost evaluation of constructed wetland for domestic waste water treatment. Journal of Environmental Biology. 36 : 1071-1074.
8. Design Manual Constructed Wetlands and Aquatic Plant Systems for Municipal Water Treatment. (1998). United States Environmental Protection Agency Office of Research and Development.
9. Dhote, J., Ingole, S. and Chauhan, A. (2012). Review on waste water treatment technologies. Int. J. Eng. Res. Technol. 1 : 1-10.
10. Fraser, L.H., Carty, S.M. and Steer, D. (2004). A test of four plant species to reduce total nitrogen and total phosphorus from soil leachate in subsurface wetland microcosms. �? Biores. Technol. 94 : 185-192.
11. Gauss, M. (2008). Constructed wetlands: A promising wastewater treatment system for small localities: Experiences from Latin America. World Bank Policy Research Working Paper Series.
12. Healy, M.G. and Rodgers, M. (2006). Treatment of dairy wastewater using constructed wetlands and intermittent sand filters. Bioresource Technology. 98 : 2268-2281.
13. Mant, C., Costa, S., Williams J. and Tambourgi E. (2006). Phytoremediation of chromium by model constructed wetland. Biores. Technol. 97 : 1767-1772.
14. Mustafa, A. and Scholz, M. (2010). Nutrient accumulation in Typha latifolia L. and sediment of a representative integrated constructed wetland. Water Air Soil Pollution. 219 : 329-341.
15. Nicolella, C., Van Loosdrecht, M.C.M. and Heijnen, J.J. (2000). Wastewater treatment with particulate Biofilm Reactors. J. Biotechnology. 80 : 1-33.
16. Paul, D., Pandey, G., Pandey, J. and Jain, R.K. (2005). Assessing microbial diversity for bioremediation and environmental restoration. Trends Biotechnol. 23 : 135-142.
17. Pearce, G.K. (2008). UF/MF pre-treatment to RO in sea water and waste water reuse applications, a comparison of energy cost. Desalination. 222 : 66-73.
18. Rizzo, L., Manaia, C., Merlin, C., Schwartz, T., Dagot, C., Ploy, M.C., Michael, I. and Fatta-Kassinos, D. (2013). Urban wastewater treatment plants and hotspots for antibiotic resistant bacteria spread into the environment a review. Sci. Total Environ. 447 : 345-360.
19. Sirianuntapiboon, S. and Kongchum, M. (2006). Effects of hydraulic retention time and media of constructed wetland for treatment of domestic wastewater. African Journal of Agricultural Research. 1 : 27-37.
20. Srinivasan, N. and Richard, W.W. (2000). Improvement of domestic wastewater quality by subsurface flow constructed wetlands. Bioresource Technology. 75 : 9-25.
21. Sudarsan, J.S., Deeptha, T.V., Reenu, L.R. and Siddharth, K. (2014). Constructed wetlands for water quality improvement, recycling and reuse. Journal of Aquatic Biology and Fisheries. 2014 : 759-763.
22. Vymazala, J. and Kropfelovaa, L. (2008) Removal of organics in constructed wetlands with horizontal sub-surface flow: A review of the field experience. Sci Total Environ. 407 : 3911-3922.
23. Zhang, L.Y., Lan, Z., Yong-ding, L. and Ying, X. (2010). Effect of limited artificial aeration on constructed wetland treatment of domestic wastewater. Desalination. 250(3) : 915-920.