Wastewater Treatment Systems for Dormitory in Urban Areas: a Case Study in Thailand

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1 Wastewater Treatment Systems for Dormitory in Urban Area: a Case Study in Thailand RSID6-ENV 04 Wastewater Treatment Systems for Dormitory in Urban Areas: a Case Study in Thailand Phonthida Sensai Lecturer, Kasetsart University, Chalermphrakiat Sakonnakhon Province Campus, Thailand, phonthida.s@ku.ac.th Samonporn Suttibak Lecturer, Kasetsart University, Chalermphrakiat Sakonnakhon Province Campus, Thailand, samonporn.s@ku.ac.th Abstract Rapid urbanization in Thailand has resulted in increasing wastewater discharged from households in urban areas. Such concern has been addressed through the provision of on-site systems in many areas. However, the performance of on-site systems could not reach effluent standards. This problem has become increasingly important especially in the case of natural treatment systems such as wastewater treatment connected with on-site systems. This paper presents a case study of applying wetland systems to treat the effluent from dormitory in KUCSC before discharging into receiving water. Two aquatic plants, Forsk were used as treatment media. Results show that the removal efficiency of BOD, TSS, TKN, TP were 34%, 50%, 50% and 9% respectively. This wastewater treatment system can be applied to improve wastewater discharged from many households or institutional areas. Such system can also be considered as an appropriate alternative for treating domestic wastewater for local government authorities in terms of low investment costs and uncomplicated treatment processes that are easier to control. 1. Introduction Urbanization and industrialization have rapidly grown particularly in developing countries. The majority of urban growth is associated with the rapid expansion of housing units such as apartments, condominiums and dormitories. These dwellings are gaining popularity because land is relatively expensive and infrastructure facilities such as water supply, sanitation, telecommunication, electricity, and road network have been moderately developed and provided in such a way that can facilitate daily living. However, this tremendous growth with increasing water usage and wastewater discharged from these dwellings have created pressure to environment and provided constraints in terms of public health, social and economic development in the future. In most urban areas of developing countries, household wastewater discharged either from an apartment or dormitory is still one of the major water pollution sources. Wastewater from these dwellings, in theory, should be treated at municipal centralized wastewater treatment plant (WWTP), but in fact most of wastewater were treated by septic tank or anaerobic tank or on-site before discharging into receiving water bodies. This situation exists because of: (i) low sewer coverage; (ii) on-site system is not complicated and managed with low investment and maintenance cost, and (iii) uncomplicated installation. However, the on-site system is unable to reach effluent standard. The effluent from on-site needs to be treated and meet wastewater quality standard before discharging into receiving water body. This study intends to present the efficiency of aquatic plant system used for treating effluent from dormitory septic tank of Kasetsart University Chalermphrakiat Sakonnakhon Province Campus (KUCSC). An ecological P. Sensai and S. Suttibak 1

2 engineering was applied to enhance capacity of wastewater treatment systems for improving the quality of discharged wastewater. 2. Current Situation of KUCSC Wastewater Treatment Systems 2.1 Wastewater Characteristics There are three KUCSC dormitories for staffs, female students, and male student. This study has focused on the 4 th building in the male student dormitory which has 80 rooms, occupying an area of 6,398 m 2, and with 400 students. The wastewater discharge is m 3 /day to the septic tank. Only one septic tank is provided in this dormitory to receive and treat the whole wastewater before discharging into open pond that is located in the nearby dormitory. Wastewater characteristic includes a ph of 7.13±0.08, BOD of 20.06±12.81 mg/l, TSS of ±16.06 mg/l, TKN of 20.65±10.39 mg/l, and TP of 1.04±0.17 mg/l. 2.2 Aquatic Plant System Effluent wastewater from septic tank is transported to aquatic plant system where the pond is covered by two natural plants namely Fors as shown in Figure 1. Treated wastewater is discharged into the constructed Nhong-kai reservoir which is used for storing rain water and also for recreation area. The characteristics of aquatic plant system have a length of 134 meters, width of 3 meters, and depth of 0.5 meters. The maintenance of the wastewater pond was done mostly by cutting unnecessary grasses. Figure 1: Receiving wastewater pond nearby male student dormitory Canna Generalis It is an ornamental lily commonly cultivated for its beautiful flowers. There are numerous hybrids all falling under the general name Canna Lily. The Canna lily has tender to hard frosts, but can be grown practically anywhere if its rhizomes are dug up during winter. These plants commonly die during cold months and only leaf out and bloom during warmer months. Plants enjoy regular watering during the warm months with full sun, part sun, or shade. They can be grown in any type of soil [1]. P. Sensai and S. Suttibak 2

3 Ipomoea Aquatica Fors A floating herbaceous vine with long trunk, branching stems containing a milky sap, with roots extending from leaf nodes. Leaves are alternate, simple, and generally arrowhead-shaped. They are 2-6 inches long and inches wide. Petioles are 1-4 inches long. Flowers are white to lavender and funnel-shaped (morning-glory-like). Fruit is oval to spherical, and is 0.5 inches long and woody when mature. Fruit capsules contain 1-4 seeds. These can grow at a rate of 4 inches per day, producing 84 tons of fresh weight biomass per acre in 9 months. Branching stems can reach 70 feet in length. The plant completely covers the water surface, reducing light penetration and dissolved oxygen in water. It alters native plants and fish communities and elevates mosquito breeding. It impedes boat traffic and clogs drainage canals [2]. 3. Aquatic Plant System Aquatic plant system is a natural treatment system that is considered as a low-cost alternative for treating municipal, industrial, and agricultural effluent. This technology may offer a low investment and maintenance cost to domestic wastewater treatment, which is especially suitable for developing countries [3][4][5][6]. Natural treatment technologies might be a good solution due to the following advantages [7]: No need to establish the sewerage system for single house or small communities. Lowering the initial cost by using cheap materials and allowing self construction. Developing a pathogenically safe, as well as aesthetic treatment unit that combines water treatment with hobby garden activities and reuse possibilities (toilet flushing). Although the plants are the most obvious components of aquatic ecosystem, wastewater treatment is accomplished through an integrated combination of biological, physical, and chemical interactions among the plants, the substrata, and the inherent microbial community. The role of the macrophytes is well-documented by several authors [8][9][10].The plants were often claimed to provide adequate oxygen via their root zones to degrade the organics and nitrogen compounds present in the wastewater. But it was demonstrated that the amount of oxygen being released by the plants to the immediate environment around the roots is limited [10]. The limited aeration around the roots ensures that anaerobic conditions will predominate, unless the organic load to the aquatic plant system is low and wetland is shallow. 4. Methodology In the experiment, the KUCSC student dormitory s wastewater from the septic tank was used. The average wastewater characteristic is given in Table 1. This research was conducted during November 2006 and February The physical characteristics of aquatic plant system and influent and effluent quality was investigated continuously twice a week for 12 weeks. The parameters such as ph, BOD, TSS, TKN and TP were analyzed. This experiment is conducted at full scale. The aquatic plant system is located at a pond near the dormitory. The pond is covered by two natural plants namely Canna Generalis and Ipomoea Aquatica Fors. The characteristic of pond shows length of 134 meters, width of 3 meters, and depth of 0.5 meters as shown in Figure 2. P. Sensai and S. Suttibak 3

4 Figure 2: The characteristic of pond 5. Results and Discussions Table 1 shows the inflow and outflow concentrations of BOD5, COD, TSS, TKN, and TP for the aquatic plant system. Influent concentration BOD ranged from 7.25 to mg/l and effluent concentration ranged from 3.14 to mg/l BOD loading rate change between g/m 3.d. The average BOD removal efficiency was found at 34%, which assures the discharge standards of the Enhancement and Conservation of National Environmental Quality Act B.E (1992) [11]. The system also acquired the removal of TSS at satisfactory level. The average inflow TSS was 25.67±16.06 mg/l and outflow was 12.83±13.06 mg/l TSS loading rate changed between g/m 3.d. This indicates that the removal efficiency of TSS was 50 %. Considering nitrogen, several form of nitrogen is in concentrated household wastewaters. Total Kjeldahl Nitrogen (TKN) consists of organic nitrogen and ammonia nitrogen is found in the majority of household wastewater. The mechanism of treating nitrogen is through the nitrification and denitrification process. The average inflow of TKN was 20.65±10.39 mg/l and outflow TKN was 10.39±3.96 mg/l with loading rate changes between g/m 3.d. The concentration reduction efficiency of TKN was 50%. In addition, household wastewater typically contains organically bound phosphorus and dissolved inorganic phosphorus. These organic and inorganic forms can be analyzed together as total phosphorus (TP). The average inflow and outflow TP were 1.04±0.17 mg/l and 0.94±0.17 mg/l TP loading rate change between g/m 3.d. Table 1: Average influent and effluent concentration and efficiency of aquatic plant system Parameters Influents Effluents % efficiency ph 7.13± ± BOD ± ± TSS 25.67± ± TKN 20.65± ± TP 1.04± ± P. Sensai and S. Suttibak 4

5 BOD removal g/m3.day y = x R 2 = TSS removal g /m3.day y = x R 2 = BOD loading g/m3.day Figure 3: Reaction between BOD loading and BOD TSS loading g/m3.day Figure 4: Reaction between TSS loading and TSS N removal g /m3.day y = x R 2 = N loading g/m3.day TP removal g /m3.day y = x R 2 = TP loading g/m3.day Figure 5: Reaction between N loading and N Figure 6: Reaction between TP loading and TP 6. Conclusions and Recommendations The purpose of the study was to evaluate the performance of the aquatic plant system. The performance is satisfactory, BOD and TSS, TKN, and TP removal performances were obtained from Fors. The results revealed that the removal efficiency of BOD, TSS, TKN, TP were 34%, 50%, 50% and 9% respectively. These findings reflect the importance of having a wetland system that employs a tertiary treatment system rather than focusing only on on-site systems. This wastewater treatment system can be applied for improving wastewater management from many households or institutional areas in urban area. Natural drainage systems can be constructed along the road functioning as the wastewater treatment and a recreation area. This system has proved to be an appropriate wastewater treatment technology for local government authorities (LGAs) in terms of low investment and maintenance costs and uncomplicated treatment processes. However, sufficient attention must be given to the organizational aspects of maintenance and operation in implementing aquatic plant systems to ensure long-term sustainability. P. Sensai and S. Suttibak 5

6 7. References [1] Trade Wind Fruit. (2008). Canna Lily, retrieved 2008 from [2] LBJWFC (2007). Ipomoea aquatica Forsk, retrieved 2008 from [3] Ayaz çs, Saygin ö. Hydroponic wastewater treatment garden: an intermittent recirculating Constructed wetland. 5 th International Conference on Wetland Systems for Water Pollution Control, vol.2, Poster 1-1. International Association on Water Quality, Vienna, Austria, [4] Haberl R, Perferler R, Mayer H. Construct wetlands in Europe. Water Sci Technol 1995 ;32: [5] Hammer DA. Constructed wetlands for treatment of agriculrural waste and urban stromwater. Chelsea, MI: Lewis Publishers, [6] Kadlec HR. Overview surface flow constructed wetlands. Water Sci Technol 1995; 32: 1-2. [7] Ayaz çs, Akça L. Treatment of wastewater by constructed wetland in small settlements. Water Sci Technol 2000; 41: [8] Brix H. Do macrophyes play a role in constructed treatment wetland. Water Sci Technol 1997; 35:11-7 [9] Wood A. Constructed wetlands in water pollution control: fundamentals to their understanding. Water Sci Technol 1995; 32:21-9 [10] Armstrong GW, Armstrong J, Beckett PM. Measurements and modeling of oxygen release from roots of Phragmites austrailis. Constructed, 1990pp [11] MONRE. (2008). Wastewater discharged quality standard, retrieved 2008 from (in Thai). P. Sensai and S. Suttibak 6