Performance Evaluation of Constructed Wetland in Treating Domestic Wastewater

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1 International Journal of Latest Research in Engineering and Technology (IJLRET) Performance Evaluation of Constructed Wetland in Treating Domestic Wastewater Rajnikant Prasad 1,Rangari P J 2, Dilendra Jasutkar 3 1 (ME Student, Dept.of Civil Environmental Engineering, APCOER, Pune) 2 (Associate Professor, Dept. of Civil Engineering, APCOER, Pune) 3 (Assistant Professor, Dept. of Civil Engineering, PGMCOE, Pune) ABSTRACT : Constructed Wetland (CW) are efficient method in reducing the contaminants from wastewater but due to presence of insufficient oxygen inside CW bed which is one of the limiting factors of efficient treatment of wastewater.a lab scale model was developed to determine the performance of naturally aerated and artificially aerated CW both are planted with Typha latifolia.this study involves determining the efficiency of Typha latifolia in polishing ph, DO, conductivity and rate of plant growth. The performances of CW were evaluated after the first phase completion (underground water treatment and fully growth of plant). In second phase the domestic wastewater was supplied to treat at different HLR and OLR and evaluated the performance of CW. The CWs were constructed by using different media which consists of bed of aggregate, charcoal and broken bricks at different height. A special PVC pipe aeration system was provided in both CWs out of which one is connected to air pump for artificial aeration and other is open to atmosphere. For aeration PVC pipes was provided in the two layers i.e. between top and middle and middle and bottom of the media. The treatment performance of domestic wastewater was evaluated after the plant is fully grown. The result shows that artificial aeration increases the diffuse DO concentration in CWs and increases the growth of plant as compared to natural aeration CW. KEYWORDS -Constructed Wetland, Artificial Aeration, Typha latifolia, domestic wastewater. I. INTRODUCTION There is municipal sewage treatment plant for cities but in small areas untreated domestic wastewater is allowed to flow directly into the open areas or on receiving water bodies. The development of effective domestic wastewater treatment system is important and at the same time the financial aspect should also be considered in deciding the effective treatment system. There are some design parameters which are proposed to improve oxygen availability by providing artificially aeration which improves the pollutant removal efficiency [8][13][17][24]. Artificially aerated vertical constructed wetland system combining artificially aeration with horizontal flow constructed wetland is effective in removing a large number of pollutants [5]. Constructed wetland technologies are natural treatment system with sand or gravel as substrate material and planted vegetation. The mechanisms of treatment in constructed wetland are complex process which can happen simultaneously or sequent [23] involving microbial degradation, plant uptake, sorption, sedimentation, filtration and precipitation. Low aeration and oxygen levels are among the limitation for better performance of constructed wetland mainly due to dieback of aquatic macrophytes that transport oxygen to the rhizosphere for microbial transportation [10].Constructed wetland technology can be applied to treat different types of wastewaters. Initially they were used to treat phenol, dairy and livestock wastewaters as well as domestic effluents. [8] [23]. The use of constructed wetlands for wastewater treatment is becoming more and more popular all over the world. Today subsurface flow CWs are quite commonly used in many developed countries such as Germany, UK, France, Denmark, Austria, Poland and Italy. Constructed wetlands are also appropriate for developing countries but they still do not have so much of research in their field.[9][1][16][6][21][4]have studied the wastewater treatment by constructed wetland where they have stated that it is the natural system to preserve a natural habitat by reducing pollution load on environment. Municipal wastewater discharge, i.e., sewerage, is one of the most serious threats to the ecosystem. Therefore, the sewage needs to be treated appropriately before the wastewater can be released into the environment [10]. A large number of technologies, such as oxidation ponds or activated sludge processes, have been applied for domestic wastewater treatment but most of these practices are expensive to erect and run [14].The mechanisms of pollutant removal in constructed wetlands involve an interaction between the bacterial metabolism, plant uptake and accumulation [12]. Water pollution is one of the main menaces to public health in developing countries. Therefore, it is important to protect the existing water sources by treating wastewater discharges from human activities and to reuse wastewater to combat water scarcity. The concept of constructed wetlands applied for the purification of various 28 Page

2 International Journal of Latest Research in Engineering and Technology (IJLRET) wastewaters has received growing interest and is gaining popularity as a cost-effective wastewater management option in both developed and developing countries. Most of these systems are easy to operate, require low maintenance, and have low investment costs [7]. In designing the good wetland, the main biological component in the constructed wetland is the aquatic plants (macrophytes). However, it is important in determining the appropriate macrophytes species that can survive in the wastewater environment, because only suitable macrophytes can treat a high concentration of pollutant in the waste water [12] II. MATERIAL AND METHOD Fig.1: Aeration system used in the model Fig.2: Sketch showing components of model 2.1 Site Description Two lab scale model for domestic wastewater treatment by artificially and naturally Aerated constructed wetland was designed to treat domestic wastewater situated in Wagholi, (N and E ) pune. The prevailing climate in wagholi area is known as a local steppe climate [48].The average annual temperature in wagholi is 25.0 C and the rainfall is 603 mm. 2.2 Development of laboratory setup Two parallel laboratory scale VFCW (Vertical Flow Constructed Wetland) (made up of plastic material) of dimension 0.3m x 0.4m (diameter x height) were uniformly designed. The units with and without aeration were designated as (Artificial Aerated Vertical Flow Constructed Wetland) and (Natural Aerated Vertical Flow Constructed Wetland) respectively. Two PVC pipes of diameter 20mm for artificial and natural aeration was laid in both unit and was laid in the layer between bottom, middle layer and top layer of the supporting medium. The bottom of aeration pipes were punched with 2mm holes as shown in Fig. 1.The support media was filled uniformly inside the two models. At the bottom of the tank brick media at a height of 120 mm from bottom of the tank, from top of bricks media charcoal media was filled to a height of 120 mm and at the top surface of charcoal to height of 120 mm aggregate was filled in the tank. For seeding of Typha latifolia locally known as pankanis collected from the local site located at wagholi were planted into each unit. Before plantation all material was washed with acid for minimum of three times and dried it in open atmosphere. After full dry the media was placed in both models. Plants were placed in CW units at a depth of 6 inch and initially it was cut from the bottom to a height of 20 cm. The characteristics are shown in the Table Page

3 ph International Journal of Latest Research in Engineering and Technology (IJLRET) Table 1: Characteristics of model Sr.no. Particular Characteristics 1 Name of plant Typha Latifolia 2 Size of model ( circular ) 400mm x 300mm 3 Area of bed m2 4 Total volume 25 L 5 Total height of bed 3600 mm 6 Total height of supporting 3400 mm media 7 No. of layers of supporting media Three 8 Depth of brick pats 120 mm 9 Depth of aggregate 120 mm 10 Plant density 56 plant per m2 11 Depth of coal 120 mm 2.3 Parameter and method of analysis The lab scale model was assessed for its performance in terms of domestic wastewater parameter ph, DO, conductivity, plant growth. The method of analysis is given in table 2. Table 2: Parameter used and method of analysis Sr. No. Parameter Methods 1 ph value, Electric ph Meter 2 Conductivity Conductivity Meter 3 Dissolved Oxygen DO fixation Method 4 Plant growth Measuring Tape III. RESULT AND DISCUSSION The study was conducted after the model was fully developed and the wastewater sample was analysed for parameter such as ph, Conductivity, DO and plant growth. The sampling in both inlet and outlet was carried out on hourly basis i.e. 4hour, 8 hour and 12 hour duration and performance was compared for the efficiency of the working model. The parameters which are tested are discussed below: 3.1 ph Parameter ph Value INITIAL VALUE HRT (Hrs.) Fig.3:Initial and final values of ph after treatment in CW 30 Page

4 DO Value (mg/l) Conductivity (µʊ/cm) International Journal of Latest Research in Engineering and Technology (IJLRET) ph is the Hydrogen ion concentration present in wastewater. The ph value goes down due to acidification process in domestic wastewater as shown in fig.3. The reduction in ph in is more as compared to. 3.2 Conductivity Conductivity INITIAL VALUE HRT (Hrs.) Fig.4: Initial and final values of Conductivity after treatment in CW It is the measure of ability of water to conduct electricity. The changes in conductivity for influent and effluent are shown in fig.4. The values of conductivity are increasing and are maximum for the than because of the DO value is increasing. 3.3 DO Parameter DO Value INITIAL VALUES HRT (Hrs.) Fig.5: Initial and final values of DO after treatment in CW DO level of influent and effluent is plotted in fig.5. The average rate of influent DO is recorded as 0 mg/l of domestic wastewater. In range of DO is increasing and achieving more efficiency as HRT is increasing due to provision of artificial aeration. In there is increase in the DO but to lesser rate as that of. 3.4 Plant Growth 31 Page

5 Height (cm) International Journal of Latest Research in Engineering and Technology (IJLRET) Plant growth No. of days Fig.6 Rate of plant growth in two models of CW The plant height mainly depends upon the supply of nutrients and amount of oxygen. The initial height of 20 cm was kept at the time of plantation and the height was recorded at the interval of 5 days. The fig. 6 it can be seen that after the plant was in the operation ant the wastewater was treated after 50 days of the plantation. Form the graph it is found that the rate of growth in the is more as compared to as the amount of supply of oxygen to their roots is more so the growth rate is more. IV. CONCLUSION On the basis of above result it shows that the aeration system enhances the air quality in wastewater due to the provision of artificial aeration system. 1. Due to acidification process in CW the ph level goes down. 2. The provided base media work as a good absorbent like a tertiary treatment. 3. The plant growth in artificially aerated system is more due to the presence of increase in diffused air content in the roots of the plant. 4. The conductivity increases due to dissolution of minerals which are present in domestic wastewater. V. Acknowledgements It is my great pleasure to present this paper. I would like to thanks Prof.Rangari P J, Prof.DilendraJasutkar who are my project guides, for helping me whole heartedly. I would also like to thank my HOD Prof. S Gawande,friend s, staff of civil department, library staff; computer lab staffs etc. without their support this article was not possible. REFERENCES [1]. Babatunde, A.O.; Zhao, Y.Q.; O'Neill, M.; O'Sullivan, B. (2008); Constructed Wetlands for Environmental Pollution Control: A Review [2]. of Developments, Research and Practice in Ireland; Environment International, 34 (1): Boca Raton, FL. [3]. BRIX H. Functions of macrophytes in constructed wetlands. Water, Sci. Technol. 29,71,1994. [4]. Dynamic Olfactometry; Journal of Urban and Environmental Engineering, v.6, n.2, p [5]. H.C. Tee, C.E. Seng, M.A. Noor, and P.E. Lim, Performance comparison of constructed wetlands with gravel and rice husk- based [6]. media for phenol and nitrogen removal, sci. Total Environ. 407 (2009), pp [7]. Hans Brix (2004); Danish Guidelines for Small-Scale Constructed Wetland Systems for Onsite Treatment of Domestic Sewage; [8]. International Conference on Wetland Systems for Water Pollution Control, Pp [9]. J. W. Leader, K.R. Reddy and A.C. Wilkie (2005); Optimization of Low-Cost Phosphorus Removal from Wastewater Using Co- [10]. Treatments with Constructed Wetlands; Water Science & Technology Vol. 51 No. 9 pp [11]. Jizheng Pan., Houhu Zhang., Wencho Li & Fan Ke, (2012). Full scale Experiment on Domestic Wastewater Treatment by Combining [12]. Artificial Aeration Vertical And Horizontal Flow Constructed Wetlands System. An international journal of Environmental Pollution, 32 Page

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