AVAILABILITY OF SUSTAINABLE SANITATION SYSTEM IN A RESIDENTIAL HOUSE

Transcription

1 AVAILABILITY OF SUSTAINABLE SANITATION SYSTEM IN A RESIDENTIAL HOUSE NAOKO NAKAGAWA 1, MASAHIRO OTAKI 1, SHINJI MIURA 2, HIRONOBU HAMASUNA 3 AND KATSUYOSHI ISHIZAKI 4 1 Graduate School of Humanities and Science, Ochanomizu Univ., 2-1-1,tsuka,Bunkyo-Ku, Tokyo, ,Japan 2 City Maintenance Technical research center, , Shinju, Shinjuku-Ku, Tokyo, 16-23,Japan 3 Nagasaki Institute of Applied Science, 536, Abama-cho, Nagasaki-shi, Nagasaki pref., ,Japan 4 Research Institute for a Sustainable Future, Waseda Univ., 513 Tsurumaki-chou,Waseda,,Shinjuku-Ku, Tokyo, ,Japan Sustainable sanitation is an approach for more ecological and sustainable water resources management. In this paper, we propose one of the new integrated waste treatment system, Organic Sanitation System which consists of a dry toilet (Bio-toilet) and an artificial wetland. The Organic Sanitation System also changes the domestic waste to soil conditioner and fertilizer for farm land. As one of case studies, Environmentally Symbiotic Housing in which people actually live using the Bio-toilet which doesn t use water and friendly to the environment is introduced. This house uses a septic tank for non-fecal treatment, too. We verified the availability of this system by analyzing the sawdust used as the matrix of the Bio-toilet and the quality of the effluent of the septic tank. As a result, it found that the weight of the sawdust is about 1/3 of its original weight after 3 months. The water content of the sawdust did not exceed 6% in any of the sampling points. In addition, the BOD and COD of the effluent of the septic tank were below 1 and 2 (mg/l) respectively, due to the low loading. Therefore, the results of this analysis proved that this system is operated well. INTRDUCTION In recent years, many symposiums concerning sanitation have been held. The background to this research is an action plan adopted by the Johannesburg Earth Summit of 22: The proportion of persons who have no access to safe drinking water and the proportion of persons who have no basic sanitation facilities shall be halved by 215. The percentages of such people are particularly high in developing countries, and the departure point for this research is the need for systems unlike conventional wastewater treatment systems to implement the action plan. Naturally, excreta and garbage produced by households had to be returned to the earth as nutrients, however, these are now treated as waste material that pollutes water bodies.

2 The Organic Sanitation System that was developed by this research is a new wastewater treatment system that incorporates a home using non-flushing toilet (Bio-toilet) that converts excreta into a reusable resource that it supplies as fertilizer or humus for organic agriculture, conserving the environments of rivers, inner waters, and reservoirs. This paper describes the actual case of coagent house that received Nagasaki City s Urban Beautification Award. Not only does this house have a superior design in harmony with the surrounding environment, it features many environment friendly innovations. It is equipped with an OM solar system and a photovoltaic power generation system, and has a Bio-toilet that does not use water and minimize the environmental load to a septic tank. The paper also describes the good results obtained concerning the state of operation of the Bio-toilet and the septic tank for a non-fecal wastewater. Location conditions and environmental measures at the house of research coagent The house of research coagent (Fig.1) is on high ground in a hillside town that spreads in a conical shape around the Port of Nagasaki. It was designed to effectively take in wind blown up along the slope so that cooling wind passes through its interior in the summer. It is a building that follows the slope and enjoys splendid view. The cutting of surrounding trees and excavation of the slope were minimized to protect its appearance. Because the district is not sewered, generally its residents either flush their toilets using a combined treatment septic tank or they Figure 1 Appearance of the house of research coagent install a pit latrine. If a pit latrine is chosen, the fecal waste has to be collected and it is necessarily This house chose a Bio-toilet that does not discharge wastewater and a septic tank was installed to treat the bath and kitchen wastewater. Bio-toilet Bio-toilet uses sawdust or chips as an artificial soil matrix to decompose the excreta to compost or even to form of gas and humus. Inside a tank, a motor gently stirs sawdust or chips. In the sawdust, the water content of the excreta is evaporated by the heat produced by biological activity. After the organic material has been composted, it is disposed of as waste material along with the sawdust for use as fertilizer. All that remains after this process are a little phosphorus, minerals, salt, and humus. Figure 2 shows the structure of the Bio-toilet. The excreta placed in the sawdust filled in the tank is fermented and decomposed as it is agitated slowly by a screw-shaped

3 rotating body. The Bio-toilet has the structure that sawdust is sent out one by one from the excreta inlet side to the removal opening side. A ventilation fan installed beside the Bio-toilet keeps the interior of the house almost completely free of the smell of the excreta. The fermentation and decomposition reduce the volume of the excreta until it can finally be used as fertilizer in dry condition. Exhaust fan Excreta inlet Excreta removal opening Motor Blower.Screw-shaped member Figure 2. Schematic of Bio-toilet Septic tank A septic tank is used as the non-fecal treatment as shown in Figure 3,4. After settlement separation and anaerobic decomposition of the non-fecal wastewater in 2 settling tanks, it flows into an aeration tank. After aerobic decomposition in the aeration tank, the supernatant fluid is drained from the settlement separation layer. settling tank aeration tank Figure 3. Non-fecal treatment (septic tank) Figure4. Structure of the septic tank

4 EXPERIMENTAL METHODS Bio-toilet In order to clarify the degree of reduction of the sawdust inside the Bio-toilet treatment, its water content, chloride ion concentration, and its ash content were measured. Sawdust was sampled from five locations inside the Bio-toilet treatment tank and each was analyzed. After approximately 6 months that is the standard period for sawdust replacement, dry composted sawdust was seen near the removal opening, so it was assumed that this is the best time to evaluate the used sawdust as a fertilizer. Figure 5,6 shows the Bio-toilet treatment tank. The cover visible in the foreground is the compost removal opening, and the toilet is above the gray pipe that can be seen in the back. The compost was sampled once a day for seven consecutive days towards the removal opening side from the toilet side of the treatment tank to investigate the state of its decomposition. The numbers indicated by 1 to 5 in Figure 5,6 correspond to the sampling point numbers on the graph. The water content was measured by finding the weight (M) of the sawdust and the weight (Md) after drying at a temperature of 15 C. The water content is defined by the following equation. M Md w(%) = 1 (1) M Figure 5. Bio-toilet treatment tank The removal opening Excreta Figure. 6. Sampling point - of Bio-toilet t k The chloride ion content concentration was measured by dissolving a fixed volume of sawdust in a stipulated volume of distilled water with 1 minutes agitation, then measuring the voltage from a chip shaped chloride ion electrode. The chloride ion concentration in each sampling point was estimated based on this voltage and the results of the measurement of the voltage in a saline solution. The ash content was measured by finding the weight of the sawdust (Mb) then heating it in an electric furnace at a temperature of 6 C for 3 hours, and measuring the residue (Ma) to calculate the ash content (α). The ash content (α) is defined by the following equation.

5 α(%) = Ma Mb 1 (2) Septic tank The water quality of influent and effluent of the septic tank was investigated. The detailed water quality analysis was measured on October 2, 23. The sampling time was 6:p.m. Then, the BOD and COD at influent and effluent were measured during 1 day at 6 hour intervals in December, 23. RESULTS AND DISCUSSION Bio-toilet Figure 7 shows the measurement results of the water content. The water content tended to decline over time. It is because the sampling points from the point closer to the removal opening has retained for longer time in the Bio-toilet. Therefore, the rate of water content becomes lower as human waste stops mixing and long time passes. The water content did not exceed 6% in any of the sampling points. Generally the criterion for appropriately performing composting is in a range from 4% to 6%, so the results of this testing proved that the Bio-toilet operated well. Figure 8 shows the chloride ion concentration measurement results. Because the chloride ion content would be unchanged at sampling point 1 to 5 (chloride originated in excreta are constant), this change is considered to depend on the weight loss of the sawdust inside the Bio-toilet. The result of weight change is shown in Figure 9. w ater content(%) sam pling point No. 5 wt(%) sam pling point No. Figure 7. The measurement results of the water content Figure 8. The measurement results of the chloride ion concentration

6 Relative weight sawdust (g) sampling specim point en No, No. ash content(%) sampling pling point No Figure 9. The weight change of the sawdust in the Bio-toilet Figure 1. The measurement results of the ash content Figure 1 shows the results of the measurement of the ash content. It s shows that the ash content did not change between No. 1 and No. 2,however, from No. 3 to No. 5, the ash content increased as the decomposition advanced. The sampling point near the removal opening was completely fermented, odorless, and dry. The compost is regularly removed and used as fertilizer in the household vegetable garden. Figure 11 is the change of the relative weight of the sawdust in the Bio-toilet. It was prepared by calculating the weight of the water by multiplying the weight of the sawdust per 1 gram of chloride by the water content, calculating the weight of the ash by multiplying the weight of the dry sampling points that were obtained by the ash content, and assuming that the remainder is organic material. It reveals that after approximately 3 months, the weight of the sawdust is about 1/3 of its original weight. The water content has the greatest impact on the weight reduction. The evaporation of the water, emission of carbon dioxide gas during decomposition, and the emission of ammonia are assumed to reduce the weight of the sawdust.

7 sampling point N ash content w ater content organic content The relative weight of sawdust (g) Figure 11. The change of the relative weight of the sawdust in the Bio-toilet Septic tank Table 2 shows the results of the measurement of the influent and the treated effluent sampled at 6: p.m. on October 2, 23. In the effluent, the BOD and COD were both between 5 and 1 (mg/l) or less, indicating that good treatment was performed. However, this was just a value at 6: p.m. in the afternoon. To clarify the state of treatment more accurately, it was necessary to observe change of the water quality over time according to the daily life cycle. In December 23, the influent and effluent of the non-fecal wastewater treatment system was sampled and its quality measured at 6 hour intervals. The results are shown in Figure 12. The quality of the influent was a little low, with BOD of 1 (mg/l), COD of approximately 4 to 5 (mg/l), and it varied over time, however no substantial fluctuation of the treated wastewater quality was seen. Thus, the BOD and COD of the effluent was a little higher than in the results of the survey made in October due to SS content.the BOD and the COD of the supernatant was also measured after the water had been allowed to stand for a while. They were 5 (mg/l) or less. It is assumed that the biological decomposition proceeded well, however, judging from its relationship with the hydraulic loading, there is a little problem with the sedimentation separation process. This system was developed as an individual treatment septic tank for wastewater including excreta. Therefore it should be improved for only non- fecal wastewater.

8 Table 2. Results of the measurement of the quality of water in the non-fecal treatment (sampled at 6: p.m. on October 2, 23) Paramete rs The influ ent The effluent ph Turbidity(TURB NTU) 17~22 12 ~14 DO(mg/l). 3~ Tempe rature( ) BOD COD SS(mg/l) Tota l Nitrogen(mg/l) Total phosphorous mg/ COD(influent) COD(effluent) BOD(influent) BOD(effluent) Figure 12. Results of the measurement of the quality of water in the non-fecal treatment(sampled on December 9, 23) CONCLUSION This paper introduced a new wastewater treatment system called the Organic Sanitation System. And as one of the actual case, the Environmentally Symbiotic Housing incorporating a Bio-toilet for fecal treatment and a septic tank for non-fecal treatment in order to reduce a loading to environment and utilize the nutrient resource was introduced. An analysis of the sawdust inside the Bio-toilet treatment tank used in this house revealed that the nearer the sawdust is to the removal opening, the higher its ash content

9 and the more advanced the decomposition of its organic material. And water content of all sampling points was kept in the optimal range. These results proved that the Bio-toilet operated well. The results of measurements of the water quality of the effluent of the septic tank revealed that both its BOD and its COD were 1 and 2 (mg/l) respectively. If precipitation efficiency is improved, they are possible to be 5-1 (mg/l). It is assumed that the biological decomposition proceeded well, however, there is a little problem with the sedimentation separation process. This system was developed as an individual treatment septic tank for water including excreta, therefore it should be improved for only non-fecal wastewater. ACKNOWLEDGEMENTS This research presents the results of the research project Research on the Development of Sustainable Sanitation Systems and their Introduction in the Water Cycle System that is a Core Research for Evolutional Science and Technology (CREST) by the Japan Science and Technology Agency. And this paper also summarizes the results of research by the Ishizaki Lab at Nagasaki University and by the Hamasuna Lab at the Nagasaki Institute of Applied Science. REFERENCES [1] Katsuyoshi Ishizaki, Shinji Miura, et al: Sustainable sanitation for sound water and nutrient cycle in watershed, The 6th Symposium on Water Resources, pp , 22. [2] N. Nakagawa, M. Otaki, K. Ishizaki: The technical trend at the low environmental load type toilets in japan, Proc. of IWA 2nd World Water Congress (held in Berlin), pp24, 21. [3] Zhen LIU, Katsuyoshi Ishizaki, et al: Recent development of dry toilets in japan, First International Conference on Ecological Sanitation, pp.91-93, 21.