Constructed Wetland Application in Septic Tank Effluent Treatment

Transcription

1 Constructed Wetland Application in Septic Tank Effluent Treatment Anggia Retno 1, Sofie Ariani 2, Idris Maxdoni Kamil 3, Barti Setiani Muntalif 4 1 anggia.retno@gmail.com 2 sofieariani@gmail.com Abstract. Septic tank with drain field is a common method for treating black water, but in these days is hard to provide land for drain field on the other hand septic tank effluent need to be treated to prevent environmental damage. This research used constructed wetland systems with subsurface flow using Pontederia cordata. Pontederia cordata is a plant that has long roots, living on wet ground conditions, and can live in polluted water, which can be used as plants in constructed wetland. This research used the palm fiber, limestone, gravel, and soil that function as a filter, forming the flow of water, microorganisms living media, and plant growth media. This study aims to determine the efficiency septic tank effluent treatment using constructed wetland with Pontederia cordata, The analysis was done by comparing removal efficiency in unplanted reactor with planted reactor. Parameter analyzed is COD, total phosphates, total nitrogen, and TSS. Efficiency of constructed subsurface flow wetland with the use of plant Pontederia cordata in treating septic tank effluent for these parameters are COD 89-94%, total phosphate 89,58±4,79%, total nitrogen 95,05±0,54%, TSS 93,89±3,53%. While in unplanted reactor the efficiency is 80,63±0,5%, phosphate 45,45±10,99%, total nitrogen 73,76±6,72%, TSS 87,62±1,84%. Keyword: COD, Pontederia cordata, wetland 1 Introduction Septic tank with drain field is commonly applied for treating black water in the rural area. However, along with the rapidly growing population, the area that needed for drain field will be hard to obtained. That caused septic tank effluent that released to the environment do not meet quality standard (based on KepMen LH no.112 tahun 2003). This condition definitely can cause damage to the environment, especially ground water contamination that can lead to community health problem. Limited land for the drain field, encouraging the modification of specification and process of septic tank with drain field system. One of the methods that can be applied is constructed wetland. A septic tank for blackwater treatment will reduce the total pollution load of a household by 25% (Nguyen et al., 2007). The expected removal efficiency of a Natural Resources Management NRM 18-1

2 Anggia Retno, Sofie Ariani, Idris Maxdoni Kamil, Barti Setiani Muntalif standard 2 m3 septic tank loaded with domestic sewage in the tropics is about 70% TSS and 50% COD (Nguyen et al., 2007). While the soak pit area only distribute septic tank effluent into the ground. In drain field process there is no quality improvement of septic tank effluent. Therefore with constructed wetland to treat septic tank effluent it is expected the quality of septic tank effluent will improved before it is released to the environment. Constructed wetland treatment systems are engineered system that have been designed and constructed to utilize the natural processes involving wetland vegetation, soils, and their associated microbial assemblages to assist in treating wastewater (Vymazal and Kropfelova, 2008). Constructed wetland can be used for treating septic tank effluents from housing complexes, providing tertiary treatment to effluents from conventional sewage treatment plants. Constructed wetlands have also been used to treat industrial, mining and agricultural wastes (Arceivala et al., 2008). The advantage of constructed wetland is able to treat wastewater with low operational and maintenance cost, beside that operational and maintenance processes is relatively easy because it using sustainable natural strength. Pollutants removal that occur in constructed wetland through several mechanisms such as sedimentation, filtration, volatilization, adsorbtion by the media particle, absorbtion, decomposition by microorganism and assimilation by plants (Vymazal and Kropfelova, 2008). Constructed wetlands are generally divided into two types as far as their water surface is concerned. They are either of the free water surface type or the subsurface water flow (Crites and Tchobanoglous, 1998). This research used subsurface flow type because it have advantages compared tho the the other type, such as there is no stagnant water thus reducing possibility of mosquito vector. And the other thing that needed to consider in designing constructed wetland is choosing media and vegetation that will be used. Media may include stone, gravel, sand, soil, palm fiber, etc. Pontederia cordata is a plant that can be used in the constructed wetland. These plants can live in wet soil conditions but does not require stagnant water to the place of its life. Pontederia cordata have extensive root system which is needed in constructed wetland. Pontederia cordata also frequently used as an ornamental plant in the garden as it has a fairly attractive blossom so that beside use as a wastewater treatment plants it can also function as ornamental plants in settlements. This study aimed to determine the removal efficiency of COD, total phosphate, total nitrogen, and TSS with the use of constructed wetland plant Pontederia Natural Resources Management NRM 18-2

3 Constructed Wetland Application in Septic Tank Effluent Treatment cordata.and to determine the difference of efficiency COD removal with various COD initial loading. 2 Methodology This research was conducted using four reactors where one reactor serves as a control (unplant reactor) and three reactors that use different initial COD loading. Here is a chart that describes flowchart of the research (Figure 1) Reactor deasign Plant selection Reactor prearation Reactor Acclimatization Reactor Operation Sampling and Measurement Data Processing and Analysis Figure 1 Research flowchart 2.1 Choosing The Plants Plants used in this research is Pontederia cordata. The reason for this is Pontederia cordata have an extensive root system, that is cm and the plant height is cm that suitable for the size of the reactor and can be applied in residential area on the real conditions. Besides, this plant growing in a sunny Natural Resources Management NRM 18-3

4 Anggia Retno, Sofie Ariani, Idris Maxdoni Kamil, Barti Setiani Muntalif climate which is fit with Indonesian climate, its cultivation is easy, and can stand with polluted water conditions. 2.2 The Design of The Reactor Design of the reactor include determine size of the reactor, the water drainage system, inlet, outlet, overflow channel, and also the determinne which media that used in the constructed wetland, the placement of the media and the amount of each media. Next is the picture of reactor design along with the type of the media used in this constructed wetland (Figure 2). Inlet Overflow Soil Gravel Outlet Lime stone Palm fiber Figure 2 Reactor design Perforated pipe 2.3 Reactor preparation Preparation of the reactor includes the step of filling reactor with media (palm fiber, limestone, gravel, soil) according to the reactor design and then planting of plants. After the plants were grown reactor filled rainwater for acclimatization stage of saturation and also plants acclimatization. Acclimatization step aims for reactor condition is stable, media is saturated so the water table will be stable, bactery has been adaptaded to the reactor condition, as well as the plant has been adapted, therefore water treatment process will occur 2.4 Reactor Operation Reactor operation begins by determining the variations of COD of waste water for each reactor. On first running for reactor 1 (unplant reactor) used COD 1,500 mg/l, as well as in the second reactor, the reactor 3 is used COD 1,000 mg/l, while the fourth reactor used in the initial COD value of 750 Natural Resources Management NRM 18-4

5 Constructed Wetland Application in Septic Tank Effluent Treatment mg/l. Waste water is inserted through the inlet pipe until it reaches a certain height of the reactor (± 32.5 liters) just below the overflow pipe. The following photo appeared front reactor (Figure 3) Inlet Gravel Palm fiber Wastewater height Lime stone Figure 3 Reactor from the front 2.5 Sampling and Measurements Sampling is done every day until the seventh day. The parameters analyzed included COD, total phosphate, total nitrogen, TSS. COD parameters are checked at the beginning of imported waste, day 1, day 2, day 3, and day-to- 7.Total phosphate, total nitrogen, TSS, checked at the beginning of wastewater inserted to the reactor and seventh day. Measurement of these parameter is perfomed in Environmental Engineering ITB. 2.6 Data Processing and Analysis The result of sample analysis will be processed so that the efficiency can be obtained for each reactor. From these results we can conclude on what is the value of COD variation that can provide the level of maximum efficiency for constructed wetland with Pontederia cordata. Removal efficiency of the reactor that use plant in the reactor will be compared with the controls to see the influence of plants on the removal efficiency. The following data processing and graphics use tha result from first and second running. Results from analysis of various parameters are compared with previous studies to assess whether the constructed wetland with Pontederia cordata successfull for treating septic tank effluent water so that can be applied in the community. Natural Resources Management NRM 18-5

6 Anggia Retno, Sofie Ariani, Idris Maxdoni Kamil, Barti Setiani Muntalif 3 Result and Discussion Waste that will be treated in this research is wastewater from septic tank effluent. In this research parameter that analyzed is the value of COD (Chemical Oxygen Demand), total phosphate, total nitrogen, dan TSS. Parameter sampling in this research is done after the reactor and plants through tha acclimatization proccess, so that the ractor condition is stable, both media, plants, and microorganism has been adapted to the ractor condition. Removal efficiency of the reactor that use plant in the reactor will be compared with the controls to see the plants s influence on the removal efficiency. The following data that showed is average data from first and second running that show standard deviation from those two runnings. 3.1 COD Removal In this research one of the parameter that analyzed is the value of COD (Chemical Oxygen Demand) which show the content of organic substances in wastewater. COD value is calculated using strong chemical oxidant in acid. In the first reactor (control) filled up by wastewater with COD value 1,500 mg/l, as well as the second reactor, so we can get the efficiency difference between the reactor that using plants (reactor 2) and reactor with no plants (reactor 1). Data that showed in Figure 4 is average data COD removal from first, second, and third running. COD value after 7 days in reactor 1 is 285,58±10,11 mg/l with removal efficiency 80,82±0,92 %. Whereas in reactor 2 removal efficiency is higher its 93,37±0,45 % The following Figure 4 is comparison of COD removal in the first day till seventh day: Figure 4 COD Removal in 7 Days in Reactor 1 and 2 Natural Resources Management NRM 18-6

7 Constructed Wetland Application in Septic Tank Effluent Treatment The comparison efficiency of that two reactor can be seen in this following graphic: Figure 5 Efficiency comparison of COD removal between reactor 1 and 2 In Picture 5, can be seen that the use of plants give a difference of efficiency. The efficiency of reactor 1 (unplant reactor) is 80,82±0,92 % while in reactor 2 (using Pontederia cordata) give removal efficiency about 93,37±0,45 %. From COD value that we get in the seventh day, it is known that using Pontederia cordata as vegetation plant can reduce COD concertation. COD removal in reactor 2 is higher than reactor 1, because there is bactery that attach on plants root, and organic matter assimilation by the plants. The following chart is the comparison of COD values decrease from the first day until the seventh day in reactor 2 (COD 1,500 mg/l), reactor 3 (COD 1,000 mg/l), reactor 3 (COD 750 mg/l): Figure 6 COD removal in 7 days for reactor 2, 3, and 4 Natural Resources Management NRM 18-7

8 Anggia Retno, Sofie Ariani, Idris Maxdoni Kamil, Barti Setiani Muntalif As we can be seen in Figure 6 that the COD tends to reduce drastically on the first day. This is due to the early days of bacterial growth in log phase so that a high metabolism and can break down organic matter quickly. While on the following days the bacteria in the wetland has reached the stage of static growth so that the reduction was relatively to be small compared to the first day. From Figure 7 can be seen that the percentage of efficiency removal in the reactor, the highest was in the second reactor which used highest initial COD value 1,500 mg/l which gives the results of 93,49±0,41%. This shows the constructed wetland with Pontederia cordata is able of processing COD in high concentrations. Next is the efficiancy comparison of the three types of reactors Figure 7: Figure 7 COD removal efficiency comparison with variation COD initial COD removal in subsurface flow wetland through bioconversion process by the bacteria that attached to the plant (e.g. roots) and also the wetland media. Performance of bacteria in the wetland is influenced by temperature, warm temperature enhance population and metabolism of bacteria conditions, while low temperature will reduce the rate of oxygen transfer (Cui et al., 2006), therefore the application of wetland in Indonesia is very suitable for tropical climate conditions that tend to have warm weather. Reactor 2 that have highest initial COD loading has been given the highest efficiency, this is cause by a limit value where COD can t be proccessed anymore by constructed wetland. So the result of COD value from 3 COD loading variation doesn t give a lot of different. And this result show that constructed wetland with Pontederia cordata can process COD in high concentration Natural Resources Management NRM 18-8

9 Constructed Wetland Application in Septic Tank Effluent Treatment 3.2 Total Nitrogen Removal The initial concentration of total nitrogen in waste water in the reactor 1 and 2 were mg/l. The value of total nitrogen on the seventh day is mg/l for reactor 1 (unplant reactor), while in the second reactor, the value of total nitrogen on the seventh day is 1-3 mg/l. Comparison of the removal efficiency betweet the two reactor can be seen in the figure below (Figure 8): Figure 8 Comparison of total nitrogen removal between reactor 1 and 2 Removal mechanism of the total nitrogen in the constructed wetland through a process of adsorption by the media wetland and also absorption by plants. Wetland plants make rhizosphere aerobic and there is presence of large number of nitrifying bacteria on root system (Sonavane et al., 2007). Besides removal of nitrogen also caused by sedimentation process, sedimentation process was influenced by the presence of plant roots and the media used in costructed wetland, in this study used the media is palm fiber, limestone, gravel and soil. Palm fiber and gravel serves to slow down or form a waste water flow path to allow sedimentation. In the Figure 8 it can be seen that the use of plant Pontederia cordata have a quite well removal efficiency of total nitrogen that is 95,05±0,54%. 3.3 Total Phosphate Removal Total phosphate removal mechanism in the constructed wetland includes filtration, sedimentation, chemical reactions in the substrate, absorption by plants, and assimilation by microorganisms (Debing et al., 2010). In this study, the value of total phosphate from waste water is 5-9 mg/l, and with the 7 days detention time a value of total phosphate in the first reactor reaches mg/l while the value of total phosphate in the second reactor reached a value of mg/l. The following chart show comparison of the removal eeficiency for total phosphate from the reactor 1 (unplant reactor) and reactor 2 (using plant) (Figure 9): Natural Resources Management NRM 18-9

10 Anggia Retno, Sofie Ariani, Idris Maxdoni Kamil, Barti Setiani Muntalif Figure 9 Comparison of total phospate removal between reactor 1 and 2 From Figure 9 we can see that the efficiency of the second reactor reached 89,58±4,79 % which shows the efficiency level better than control reactor. This efficiency value does not differ significantly with LH Cui research that provides 93-98% efficiency rate. This shows the constructed wetland system is quite well in treating the total phosphate. 3.4 Total Suspended Solid Removal Total Suspended Solid is one of the parameters that need to be treated in septic tank effluent because its value exceeds the quality standard (KepMen LH no 112 tahun 2003). In this study the value of TSS in the initial wastewater is mg/l, while the value of TSS by quality standard is 100 mg/l. Therefore, treatment is needed before the septic tank effluent release into the environment. In this study, by using seven day detention time TSS reducing to mg/l in reactor 1 (unplant reactor) and 4-13 mg/l for reactor 2 (using plants). Natural Resources Management NRM 18-10

11 Constructed Wetland Application in Septic Tank Effluent Treatment Figure 10 Efficiency comparison of reactor 1 dan 2 in TSS removal Based on Figure 10, constructed wetland with Pontederia cordata is capable of removing TSS with efficiency 95.54±2.94%. Value is not much different from previous research (Vymazal, 2005) that mentions the number of allowance for TSS by subsurface flow wetland ranged from 87-99%. The effect of media used in the constructed wetland had a big influence on the TSS removal efficiency caused TSS removal mechanism is sedimentation and filtration. One important function is as a wetland waste water filtration units, water will flow through the wetland and the suspended solid will be trapped by the roots of plants and settle out (Nicolic et al., 2009). In this research, the removal efficiency of TSS can reach 93,89±3,53% due to the use of palm fiber as a medium for wetland that can serve as a good filtration units, the presence of gravel also play a role in TSS removal because it slows the flow so that the solid can be precipitated. In addition Pontederia cordata has a long and extensive root thus be able to trap wastewater so that the value of total solid in the effluent will decrease with a significantly. In this research can be seen that the concentration of COD, total phosphate, total nitrogen, and TSS in reactor 1 (without plant) was also decreased although the level of efficiency is not as big as in the reactor thar using plants. This shows that removal of COD, total phosphate, total nitrogen and TSS is also influenced by the media used in constructed wetland. This similar with the literature Vymazal and Kropfelova (2008). From the results, it can be concluded that the selection palm fiber, limestone, gravel, and soil is good to treat of waste water with such characteristics in the study. Natural Resources Management NRM 18-11

12 Anggia Retno, Sofie Ariani, Idris Maxdoni Kamil, Barti Setiani Muntalif 4 Conclusions Constructed wetland with Pontederia cordata are expected to apply for treating septic tank effluent. Results from this study is the use of Pontederia cordata on wastewater treatment gives much better results than reactors that do not using the plants. COD removal efficiency of this study was 93,37±0,45% for the initial COD 1,500 mg/l, 92,43±0,54% for the initial COD 1,000 mg/l, and 89,98±1,63% for the initial COD 750 mg/l. While the removal efficiency for total phosphate was 89,58±4,79%. For total nitrogen removal efficiency reached 95,05±0,54%. While removal efficiency for TSS reaches 93,89±3,53%. While in unplant constructed wetland the efficiency are COD 80.63±0.5%, total phosphate 45,45±10,99%, total nitrogen 73,76±6,72%, TSS 87,62±1,84%. The result show that sub-surface flow constructed wetland with Pontederia cordata capable to treat septic tank effluent water with a very good level of efficiency. From the research results can also be concluded that the selection of the media will inevitably impact on the constructed wetland treatment mechanisms. It is shown from the removal efficiency in the reactor 1 which did not use plants, although the results are not as significant as the reactor that using plants. The result of this research is the sub-surface flow constructed wetland with Pontederia cordata is able to treat septic tank effluent to meet the quality standard of domestic waste water based on a KepMen LH no 112 tahun References [1] Arceivala, Soli J., and Asolekar, Shyam R Wastewater Treatment For Pollution Control And Reuse, Third Edition.Tata Mgraw Hill, pages [2] Crites and Tchobanoglous Small & Decentralized Wastewater Management Systems. McGraw-Hill Science, pages [3] Cui, L.H., Liu, W., Zhu, X., and Huang, X.H Performance of Hybrid Constructed Wetland System for Treating Septic Tank Effluent. Guangzhou: Journal of Environmental Science vol.18 no.4 pp [4] Debing, J., Baoqing, S., Hong, Z., and Jianming, H Chemical Oxygen Demand, Nitrogen and Phosphorus Removal by Subsurface Wetlands with Phragmites Vegetation in Different Model. Beijing: Journal Life Science, Vol , No. 2, pp [5] Kementrian Negara Lingkungan Hidup Baku Mutu Air Limbah Domestik. Jakarta: Kementrian Lingkungan Hidup Natural Resources Management NRM 18-12

13 Constructed Wetland Application in Septic Tank Effluent Treatment [6] Nguyen, V.A., Pham, T.N., Nguyen, H.T., Morel, A., and Tonderski, K.S Improved Septic Tank With Constructed Wetland A Promising Decentralized Wastewater Treatment Alternative in Vietnam. NOWRA 16th Annual Technical Education Conference & Exposition. Paper XI- RCS [7] Nikolic, V., Milicevic, D., and Milenkovic, S Wetlands, Constructed Wetlands and Their s Role in Wastewater Treatment With Principles and Examples of Using It in Serbia. Serbia: Journal Facta Universitatis, Series: Architecture and Civil Engineering, Vol. 7, No 1, pp [8] Setiyawan, Ahmad Soleh Optimasi Efisiensi Pengolahan Efluen Reaktor Anaerobik Bersekat Dengan Menggunakan Rekayasa Aliran Pada Wetland. Program Studi Teknik Lingkungan, Institut Teknologi Bandung. [9] Sonovane, P.G., Munavali, G.R., and Ranade, S.V Feasibility of Constructed Wetland Treatment System for Septic Tank Effluent. Journal of IPHE vol No.3. India [10] Vymazal, Jan Horizontal Sub-surface Flow and Hybrid Constructed Wetlands System for Wastewater Treatment. Durham: Journal Ecological Engineering, Vol.25, Issue 5, pp [11] Vymazal, J., and Kropfelova, L Wastewater Treatment in Constructed Wetlands with Horizontal Subsurface Flow. Springer Science + Business Media B.V Natural Resources Management NRM 18-13