SOLUTION FOR WASTEWATER TREATMENT IN RURAL SCHOOL IN SARAWAK, MALAYSIA: A MODIFIED FLUSH TOILETS WITH RURAL BIOGAS SYSTEM

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1 SOLUTION FOR WASTEWATER TREATMENT IN RURAL SCHOOL IN SARAWAK, MALAYSIA: A MODIFIED FLUSH TOILETS WITH RURAL BIOGAS SYSTEM Peter Sawal 1, Tang Hung Huong 2, Marie Sigvardt 3 1,2 Natural Resources and Environment Board, Malaysia 3 DANIDA-NREB Rural Ecosan Project, Malaysia ABSTRACT Solutions for proper sanitation of blackwater in remote rural areas have been the agenda for many international and national environmental agencies for decades. To manage the public health risk and to recycle its organic matter and nutrient, many projects with different treatment configurations have been introduced. In Sarawak, Malaysia, a pilot project integrating modified flush toilets with a canal system and a 100m 3 biogas tank in a rural boarding school was embarked in The canal-flush toilet system aims to reduce the total amount of flush water from 250 boarding students to approximately 1,000 litre of wastewater per day, by flushing only once per day. This allows a retention time of at least 45 days to sterilise wastewater in the biogas tank and making the fertiliser safe for application and at the same time, it solves the long-time prohibitive issue of connecting flush toilets to a functional biogas system, as too much blackwater are traditionally being generated using flush toilets. On the other hand, to increase volatile solids for anaerobic digestion for methane production in a biogas system, organic solid waste from food preparation, and oil and grease trapped at the school kitchen are transferred to the biogas system as additional input. These high BOD organic solid wastes improve the system as human excreta is known to contain a very low carbon quantity that limits the biogas production. The biogas is currently used for food preparation in the school kitchen. To date, the system has been proven to work successfully and for the first time, the uncertainty on combining flush toilet with biogas plant has been overcome. The findings are very promising for future projects in rural areas, all over the world. Keywords: ecological sanitation; rural sanitation; blackwater recycling; rural wastewater; rural biogas 1.0 INTRODUCTION Solutions for proper sanitation of blackwater in remote rural areas have been the agenda for many international and national environmental agencies for decades. Sarawak, a state in Malaysia located on the island of Borneo, is no difference as wastewater is currently only partially treated. Greywater 1 is often discharged untreated into the nearest waterway, whereas blackwater 2 typically undergoes treatment in septic tanks before it is discharged into the environment. These septic tanks do not work properly and even a functional septic tank is only capable of reducing organic matters with approximately 50% and the removal of nutrients and pathogens are non-existing (Lynghus & Larsen, 2004). This results in a high pollution load to the environment, imposes health risk of transmitting infectious diseases to people washing, bathing and fishing downstream of the discharge and at the same time, wastes its nutrients content and energy resources. Therefore, to manage the public health risk and to recycle organic matter and nutrients in wastewater, a pilot project integrating 1 Greywater consists of wastewater from showers, sinks and other in-house wash water outlets and constitute approx. 90% of the total wastewater (Bjerregaard,2004) 2 Blackwater consists of faeces, urine and flush water and constitute approx. 10% of the total wastewater (Bjerregaard, 2004)

2 Oil & Grease Food Waste Black Water (Urine, Faeces, Flush Water) modified flush toilets with a canal system and a 100m 3 biogas tank in a rural boarding school was embarked. The pilot project was part of the Sarawak Government-DANIDA Urban Environmental Management System Project and the system was established in ECOLOGICAL SANITATON AND BIOGAS PROJECT AT SMK TEBAKANG SERIAN, SARAWAK Sekolah Menengah Kebangsaan (SMK) 3 Tebakang, a rural boarding secondary school situated about 70 km from Kuching City was chosen for the project due to two factors: 1) the school has a high student population (around 1600) i.e. high concentration of people discharging from one point; and 2) the school is very active in promoting environmental conservation to its staff and students. Before the project was implemented, the type of toilets used in the school were squatting with a single flush of about 9-12 litres. Blackwater underwent primary treatment in septic tanks and effluent was discharged into drain; the septic tanks were not regularly desludged unless blockage occurred, as desludging cost is too high due to the location far from the City. 2.1 Project Concept and Design The objective of the pilot project was to achieve a high level blackwater sanitation, at the same time the waste materials was converted into gas for cooking and recycled into fertiliser. In the remote rural area of Sarawak, the alternative supply of gas and fertiliser is very costly and difficult. As the existing rural wastewater system is already a separated management of blackwater and greywater, the separate handling of the blackwater for ecological sanitation was facilitated. Traditional solution of recycling the blackwater using dry toilet is not favourable in the context of Sarawak where body cleansing is practised. Therefore it was decided to test a solution that allows waterborne transfer of the blackwater. Two factors have to be taken into account for such solution: (1) a minimum Canal Toilets Compost/Fertiliser retention time of 45 days in the biogas plant to sterilise wastewater to ensure the end product is safe for application as fertiliser and (2) a proper C/N ratio waste to generate biogas. After various studies on technologies, it was decided to test the use of modified traditional canal system, allowing waterborne transfer of the blackwater, but reducing the required amount for flush water. Two toilet buildings (one 6-toilets and another with 9-toilets catering 250 girl pupils) were renovated to install the canals. Solid Kitchen Mixing Chamber Biogas Reactor Expansion Chamber Drying Bed Liquid Slurry for banana at valley Methane Gas for Cooking Figure 1: The process at the Ecological Sanitation and Biogas Project at SMK Tebakang, Serian 3 National Secondary School

3 It was further decided to install a biogas plant of traditional Chinese design to treat waste materials: blackwater from these toilets as well as food wastes and oil and grease from the school kitchen. The biogas generated is piped back to the kitchen as cooking gas and the end product, after liquid-solid separation using a drying bed, is used as compost/fertiliser. Figure 1 shows the processes and components of the project. 2.2 Waste Materials Blackwater (human excreta) has a low carbon quantity which does not encourage the generation of biogas. Therefore, in order to increase the generation of biogas as well as to attain a correct C/N ratio, food waste and oil and grease are added (FAO, 1996). The school kitchen prepares all daily meals for the 1600 pupils and the school staff, generating high amounts of solid organic food waste, suitable to increase volatile solids content for anaerobic digestion in biogas plant. In addition, a 1,700L oil and grease (O&G) trap was installed at the outlet from the kitchen. As Asian cooking generates a high amount of oil and grease, installing the trap and using this material as waste input for the biogas plant, significantly reduces the pollution load of the greywater discharged. A baseline survey conducted on the average daily production of Biochemical Oxygen Demand (BOD) available for the biogas plant showed that urine and faeces from 250 girl pupils provide 6.25kg BOD, 305 kg of food waste from the school kitchen provide 98.7kg BOD, whereas 36.7kg oil and grease from the O&G trap provide 25.9kg BOD. This adds up to 132kg BOD per day. 2.3 Canal-Flush Toilet System As the size of the biogas digester chamber depends on the volume of blackwater, and given the requirements for 45 days retention time, and too much water will despair the functionality of the biogas system, the precondition for establishing a solution is to reduce and regulate the amount of flush water used. This was achieved by constructing a modified canal-flush toilet system consisting of non-flush squatting pans with a bowl size equivalent to those of dry toilets, in combination with a Canal Toilet System. Figure 2: The original Canal Toilet System (Reference: Mathissen et al.) The original canal toilet system (see Figure 2) was developed primarily as a solution for blackwater flushing in areas with water shortage and has among other been implemented in several African countries. In the original design, greywater from showers and wash basins was used to flush the canal, in an uncontrolled manner. The use of greywater resolved the water shortage for flushing. In Sarawak, the issue was not water shortage, but the need to reduce the amount of flush water to improve the function of the biogas plant. The use of greywater was therefore changed into water tank placed on top of the toilet building and sized for the required volumes to flush the number of toilet lots (see Figure 3). The canals are flushed by opening the valves at the water tank once per day. The modified system allow the use of a limited volume of cleansing water and thus does not require any change in habits for people preferring cleansing with water rather than toilet paper, as it is the custom among the local communities. Urine and faeces from the toilets drops through toilet pipes into a canal (toilet sewer) which retains a permanent water level at

4 15cm with the construction of a bump in the end of the canal. The mouth of the toilet pipes is located below the water level in the canal thus creating a water lock and preventing bad odour. Figure 3: The modified Canal Toilet System To further reduce the blackwater volume, the original designed canal which is constructed as a 13m long and 40cm wide rectangular concrete drain was modified and constructed using a 38cm diameter half pipe (see Figure 4). With the modification, the retained water volume was reduced with 44% down to 0.44 m 3 from 0.78m 3 water. In term of required flush volume, it was reduced from 840 L to 470 L (Chemsain, 2005). Figure 4. Half pipe canal toilet system (Reference: Chemsain) 2.4 Toilet Design With the canal system to flush the blackwater, no additional flush water is required for the toilets. Pans traditionally used for dry toilets could therefore be used. From a wide range of toilet designs and after consideration on maintenance and the social perception by the pupils, modified non-flush squatting pans with a bowl size equivalent to those of dry toilets 4 was selected as a feasible solution. As this toilet design is new, customized squatting pans had to be made. 2.5 Chinese Fixed Dome Biogas Plant After an assessment on the requirement for maintenance, the Chinese Fixed Dome Model biogas plant, which has an underground digester with a fixed concrete dome on the top, was chosen. This type of plant is expected to last for years depending on level of 4 The standard bowl size of ordinary flush toilets is 10cm whereas dry toilets is 20cm

5 maintenance (FAO, 1996). The plant consists of three main parts: mixing chamber (inlet), digester chamber, and then displacement tank (expansion chamber) (Koottatep, S. et al.). (See Figure 5) To manage the risk of public health, blackwater is designed to directly flow into the biogas digester via an underground pipe, whereas food waste and oil and grease are delivered manually and mixed at an open inlet. The biogas tank was sized 5 with a capacity of 100m 3. As discussed earlier, to achieve optimal anaerobic digestion and biogas production, the C/N ratio of the input material must be right and the percentage of solids of the total input material has to be around 8%. As oil and grease has a very high C/N ratio (Rashid & Figure 5: The Chinese Fixed Dome Biogas Plant Voroney 2004), the mixing with blackwater and solid food waste has a positive effect on the biogas production. To ensure the end product is safe to use, the sterilisation of the blackwater to eliminate pathogens and other parasites is essential. The biogas plant is designed for mesophilic digestion with a temperature ranging between o C to eliminate pathogens with the designed retention time. Further advantages of this design include avoidance of bad odour and minimum maintenance requirements (Schiffmanm, 2001). 2.6 Usage of the end product After the anaerobic digestion, the slurry runs from the expansion chamber (also named displacement tank) into a drying bed for solid-liquid separation. With the aid of gravity, the liquid slurry flows through a pipe down into a garden area, which is grown with banana. The remaining solid slurry is dried to produce a solid fertiliser/compost. Reuse of human waste is not a new subject; there are many examples of urine and faeces being used as fertiliser. Records among others show that this has been practised in Syria for more than 1000 years (Peasey, 2000) and in China for nearly 3000 years 6 (Shiming). The end product from a biogas plant contains higher nutrient value as the nitrogen does not evaporate during anaerobic digestion. It rather increases as a percentage of total solids, and moreover is converted into a form that is easier absorbed by plants (Reddy et al., 1994). 3.0 FINDINGS 3.1 Water Usage and Flushing With the canal flush toilet system in combination with dry squatting pans, the blackwater is reduced by nearly 85% or approximately 6,500L per day. The daily blackwater volume from 250 pupils using ordinary full flush toilets is estimated at about 7,725L whereas volume using the 2 canal flush toilet systems is only 1,225L (see Table 1). 5 It is not economic to manually construct a biogas plant using cement and brick if the size of the biogas plant is more than 100m 3 (Koottatep, S., 2007) 6 Until the 1980s use of organic fertiliser was more popular than chemical fertiliser and human excreta continue to be used in approximately 30% of agricultural land (Shiming)

6 In order to identify how much water is required to ensure a sufficient hydraulic head to flush the canal, water tanks of the capacities of 750L and 1100L were installed. After half a year monitoring, the flush water were determined at 450L and 550L respectively for the 6 toilet and 9 toilets buildings. To determine the best option for reducing water usage for body cleansing and cleansing of the toilets, the 6-toilets building was installed with water sprays Table 1: Estimation of Blackwater volume Toilet system Flushwater Faeces and urine* Full flush toilets (10L x 4 flushes/ day for 250 pupils)* whereas the 9-toilets building was installed with water taps at each toilet lot. The water measurements revealed that the usage of water for cleansing in the 9-toilets building was more than 100% higher than at the 6-toilets building. Therefore it is highly recommended to use water sprays to reduce water usage. To test the efficiency of the canal system with a bump at the end of the canal to retain the water, another option, in the form of a modified valve which retained the same amount of water as the bump, was originally installed at the 9-toilets building. As anticipated, the pupils faced difficulties in opening the valve as it was too tight and hard. Furthermore the pupils tended to forget to close the valve after flushing, imposing a risk that water keeps flowing into the biogas plant. On the other hand, the bump solution at 6-toilets building proved functional, thus the valve was removed and substituted with a similar bump. 3.2 Biogas Generation To initiate the anaerobic process in the biogas plant, chicken dung (instead of pig manure to avoid the sensitivity of Muslims pupils and staff) were used. Subsequently, only blackwater, oil and grease and food waste were used to continuously feed the digester. During the first half year monitoring, the wastes delivered from kitchen remained stable at approximately 200L per day, while at the last monitoring period in 2009, the waste delivered had been reduced to approximately 120L. In the earlier period, the manometer readings at the biogas plant were ranged between 40-48cm whereas in the latter period, they were levelled only at 16-20cm. From Figure 6, these meter readings interpreted an average generation of biogas at 24m 3 and 10m 3 for the two periods respectively. The reduction was due to reduced efforts to deliver the food waste and oil and grease from the kitchen (see section 4). The energy content of the biogas generated was tested by boiling water. Table 2 showed the times required to boil 3L of water boiling using two different gases. From the results, the energy of the biogas is obviously lower than of Liquefied Petroleum Gas (LPG). This is realistic as biogas has its calorific value only at 20 mega joule per cubic meter (20MJ/m 3 ) compared to LPG with approximately 94MJ/m 3. Currently, the gas is used mostly to boil the water in kitchen. Table 2: The Times Required Boiling 3 L Water Type of gas Biogas Liquefied Petroleum Gas (LPG)* Time to boil (minute) * The school uses LPG for cooking Total blackwater/ day* 7500 L 225 L 7725 L Canal** (1 x 500L flush/building/day) Total blackwater reduction from full flush toilets to Canal Toilet System 1000 L 225 L 1225 L 6500 L *Calculation based on 250 pupils using the toilets 75% of the day (school time and weekends are partly excluded) ** 6-toilets building flushes 450 litre whereas 9-toilets building flushes 550 litres per day

7 Beside the energy comparison, a 5-working days monitoring was conducted to estimate the biogas generation rate (per hour). The manometer readings were recorded immediately after cooking and a certain period (X hours) after cooking on the monitoring days. Table 3 shows the biogas generated per hour ranged 0.6-3m 3. However, no generalisation can be made as the actual weight and types of wastes supplied were not properly recorded (See Section 4). Table 3: Biogas Generated Per Hour Day 1 Day 2 Day 3 Day 4 Day 5 Manometer Immediately after cooking reading (cm) X Hours after cooking Biogas generated in X Hours (m 3 ) X Hours Biogas generated per hour (m 3 ) Figure 6: The manometer reading (cm) vs. Actual Gas Volume (m 3 ) (Reference: Koottatep. S, 2007) 4.0 SOCIAL OBSTACLES Even though the introduced system proved its functionality, the project faced some social barriers in its implementation. These are: (a) The gardeners and kitchen staff are reluctant to record the types and volume of solid wastes delivered as well as the biogas generated and used, as this is considered too troublesome for them; (b) The biogas plant was placed close to a new planned school kitchen. However, the new kitchen has not been built, leaving the distance between the plant and the kitchen at about 380m in a hilly terrain. At the same time the solid kitchen waste and oil and grease are very heavy. The gardeners were therefore reluctant to carry the waste from the kitchen to the biogas plant as this is an extra work with no additional allowance paid. (c) The modified squatting pan with a bowl size equivalent to those of dry toilets has given chances for dumping of unwanted things such as mineral bottles, slippers, woman pads, etc. into the canal system, purposely or not. To prevent these unwanted things getting into the biogas plant, a grill was subsequently installed at the junction where blackwater from 2 toilet buildings merge and flow into the inlet pipe to biogas digester. (d) The long gas pipe from the biogas digester to kitchen resulted in few incidents of accidentally breaking the pipe by hoe and causing the gas to leak. This type of incidents always happens during the period when the school performs their regular school cleaning.

8 5.0 CONCLUSION To date, the system has been proven to work successfully and for the first time, the uncertainty on combining flush toilet with biogas plant has been overcome. However, many improvements can still be made to the system. It has been decided to change the usage of the biogas to a water heater for bathing, as the distance to the current kitchen are too long. A survey was carried out and confirmed that the idea was favoured by the girl pupils. The improvement works are currently being carried out. However, regardless how the biogas will be utilised, the consistency of waste input to be delivered to biogas plant must be sustained. 6.0 REFERENCES 1. Bjerregaard, D., Urban Ecological Sanitation Kuching is Paving the Way. The Natural Resources and Environment Board, Sarawak Malaysia 2. Biogas Utilization. Available from: ML. 3. Etnier, C. & Jenssen, P., The human waste resource in developing countries: Examples of and options for reuse of nutrients in agriculture and aquaculture. Department of Agricultural Engineering, The Norwegian Agricultural University in collaboration with Centre for International Environment and Development Studies, Noragric, Norway 4. Chemsain, UEMS Project, Sg. Bintangor Catchment, Satok, Kuching, Sarawak. Oil and Grease Monitoring Report. Chemsain Konsultant Sdn. Bhd., Sarawak, Malaysia 5. FAO, Biogas technology: a training manual for extension. Sustainable Development Department, Food and Agriculture Organization of the United States (FAO), US 6. Il-I, SNV Cambodia. Evaluation Study for Biogas Plant Designs. Final, September 2005, Consulting Engineers, Mekong 7. Koottatep, S. et al. (undated). Bio-gas: GP Option for Community Development. Asian Productivity Organization 8. Koottatep, S., 2007, Personal communication 9. LGED (Local Government Engineering Department) (undated). Design of Biogas Plant. Biogas Training Center (BRC) Chendu, Sichuan, China 10. Liquefied Petroleum Gas. Available from Lynghus, H. & Larsen, I., Sarawak Government/DANIDA Urban Environmental Management System Project Sarawak, Malaysia. Framework Plan for Integrated Wastewater Management for the City of Kuching, Sarawak. NREB, Sarawak, Malaysia 12. Mathissen et al. (undated). The Sewer Toilet. Sanitary systems designed to save water through re-use Misereor. Germany 13. Peasey, A., Health Aspects of Dry Sanitation with Waste Reuse. Water and Environmental Health at London and Loughborough (WELL), London School of Hygiene and Tropical Medicine, London 14. Rashid, M.T. & Voroney, R.P., Land Application of Oily Food Waste and Corn Production on Amended Soils. American Society of Agronomy, 96: , USA 15. Reddy, A. K. N. et al., Community Biogas Plants Supply Rural Energy and Water: The Pura Village Case Study in Energy as an Instrument for Socio-Economic Development. Paper prepared for the workshop on Biogas Technology for China, at the China Center of Rural Energy Research and Training, Beijing, November Schiffman, S. J. et al., Odor: Quantification and Health Impacts. Medical Psychology Duke University Medical School, Durham 17. Shiming, L. (undated). The Utilization of Human Excreta in Chinese Agriculture and the Challenge Faced. South China Agricultural University, China