Small-Scale Scale Domestic Wastewater Treatment Technology in Japan, and the Possibility of Technological Transfer

Transcription

1 Small-Scale Scale Domestic Wastewater Treatment Technology in Japan, and the Possibility of Technological Transfer Motoyuki MIZUOCHI Asian Environment Research Group National Institute for Environmental Studies The importance of small scale domestic wastewater treatment technology There is a trend in domestic wastewater treatment in which large city areas are accommodated more readily than medium and small city areas, or rural communities. Locally suitable technology that is adaptable to local social and economic conditions is sought in developing countries, but it is difficult to transfer the general Japanese technological system without modification. ication. Low cost system for construction and maintenance is needed. This report gives an overview of Japan s s domestic wastewater treatment and small-scale scale treatment technology, and discusses cases of technological systems that are highly likely to be transferred referred to technology development trend in China and example of technical transfer from Japan.

2 Classification of domestic wastewater Toilet Domestic wastewater Night soil Bath Wash basin Gray water Kitchen Washing machine Domestic wastewater Gray water Night soil Treatment system Gray water Night soil Sludge Effluent Municipal sewerage Rural community sewerage On site system Night soil TP Sludge treatment system Incineration Reuse Vault toilet Public water area Land fill site The flow diagram of domestic wastewater treatment in Japan

3 The outline of domestic wastewater treatment situation in Japan(2005 Unit:million person) 合併処理 On site sewerage 浄化槽, 1128, 9% 単独処理 On site sewerage only 浄化槽 for, night soil 953, 7% 農村集落 Rural community 排水処理 sewerage 事業, 352, 3% くみ取り Vault toilet, 1474, 12% 下水道 Municipal, sewerage 8802, 69% 2,427 million person s s (19% of the total population) gray water was discharged without any treatment in Japan at the end of Representative small scale domestic wastewater treatment technology Aerobic Sludge suspension Biofilm Natural treatment Anaerobic Septic tank Imhoff tank Vault toilet (Storage) Only Storage Utilization Oxidation ditch Contact aeration (Jhokaso) Rotating biological contactor Trickling filter Soil trench Constructed wetland Pit latrines Double vault latrines Compost latrines Biogas plant

4 The coverage rate of domestic wastewater treatment in areas with a population scale at the end of 2006 in Japan Coverage rate (%) More than 1,000, ,000~ 1,000,00 300,000~ 500, ,000~ 300,000 Scale of the population ,000~ 100, Less than 50,000 Total population Covered population Number of Cities, towns and villages 2,734 2, , ,738 1, ,046 1,955 2,199 2,480 1,436 1, ,263 Unit of population: million The number of Municipal WWTP less than 5,000m 3 /day according to the kind of treatment process at the end of 2004 in Japan Process Nutrient removal (Activated sludge) Conventional activated sludge Oxidation ditch Extended aeration SBR Contact aeration Step aeration Rotating biological contactor Others Total Number of WWTP ,049 Oxidation ditch process excelled in WWPT less than 5,000m 3 /day

5 Small scale municipal sewerage Oxidation ditch process With respect to sewage facilities, 1,049 small-scale treatment facilities capable of treating 5,000 m 3 or less of water per day were in operation at the end of FY 2004, and 70% of sewage facilities adopted the oxidation ditch process. Though the oxidation ditch process is advantageous in terms of maintenance because primary sedimentation tanks are unnecessary, the treatment and disposal of the large volume of sludge generated becomes a major issue. Johkaso system in Japan Johkaso for 5-10 persons (individual house) Johkaso for persons (apartment, public place, etc.) Johkaso is an on-site treatment facility that has been technologically developed uniquely in Japan. In Japan, human waste was treated as manure for a long period of time, however, because chemical fertilizers were popularized after World War II to the high economic growth period, and there was an increasing demand for flush toilets, on-site treatment facilities without the need for pipes became widespread.

6 Type of Johkaso (Tandoku( and Gappei) Gappei Gappei Johkaso treats night soil and gray water together same as municipal sewerage. Tandoku Tandoku Johkaso treats only night soil. In this case, gray water is discharged without treatment. This type of Johkaso was supposed to be allowed to be used until 2001, but many of them are still being used now. Rural community sewerage (Agricultural community wastewater treatment programs) Contact aeration 51~2, ~10,000 SBR Oxidation ditch Agricultural community wastewater treatment programs are intended to provide domestic wastewater treatment facilities for a single or multiple rural communities where domestic wastewater treatment facilities have not been sufficiently provided. A treatment process is being indicated in stages for the treated population of from 51 to 10,000 (JARUS type) 1,000~10,000

7 One of Japanese technical trend: Soil covered gravel contact aeration process Background:Low cost system for construction and maintenance by local governments overseeing sewerage services and facing more difficult financial conditions. Characteristic: It t can be designed in response to the varied size of the treated population by relatively simple structure. Producing almost no odor from the treatment facilities because the tops of the treatment facilities are covered with soil. Lower sludge generation This process was developed 25 years ago, and it has recently been adopted for sewage treatment facilities. Same local government has been selected this system for small scale municipal sewerage WWTP Soil covered gravel contact aeration process This system is designed for small scale domestic wastewater treatment against the activated sludge process family based on the contact aeration process. This system require relatively larger land area than the activated sludge process family like the oxidation ditch process. But this system has highly economic value. Contact aeration process using gravel with covered the top in the soil This is not new process, but is a reevaluated process in now for small scale system like sub hundreds cubic meters sewage scale.

8 Cross section of the soil covered gravel contact aeration process An actual constructive state Iki-city (Nagasaki pref.) Wastewater Treatment Plant Capacity: 640m3/day

9 A construction example:on site facility for 50 personns Adaptation to the middle scale on site facility ( persons) Condition of trial run and adjustment after the end of the construction

10 Johkaso system Example of technical transfer related small scale treatment system from Japan led by China -Factory production type- JICA Lake Taifu water quality restoration project(china ) MOE Guizhou Province water environment protection cooperation project (China 2000) -On site Construction type- JICWELS Johkaso system introduction project (Indonesia ) 1996) Soil treatment system -Nutrient removal type soil trench system- MOE Guizhou Province water environment protection cooperation project (China 2000) -Multi soil layer system- JICA grass-roots roots project (NPO Green Earth Network 2003) Factory production type JICA Lake Taifu water quality restoration project MOE Guizhou Province water environment protection cooperation project

11 Problems of factory production type Johkaso technology transfer in China Grasp of the situation around Johkaso in China was insufficient. Grasp of demonstration effect compared with social situation in China was insufficient. Possibility of the adaptation of Johkasou in Japan was not examined. Examination of the structure matched with the Chinese situation is short. Feasibility of the maintenance was not examined enough. Chinese Jhokaso Rippled effect of technical transfer was insufficient Technical transfer of the on site construction type Johkaso Japan International Corporation of Welfare Services (JICWELS) Indonesia 1995~ In Japan, Johkaso used to be mainly on site constructed, but they have been replaced dominantly by factory-produced Johkaso made of FRP due to soaring labor costs, and in order to secure the performance of Johkaso. Because labor costs are not so high in many developing countries, a method with a higher percentage for labor costs for the provision of Johkaso becomes advantageous to lower construction costs. It is thought that the technological transfer of field construction technology for Johkaso should be continuously stressed in the future.

12 Land treatment facility:nutrient removal type soil trench MOE Guizhou Province water environment protection cooperation project 40% Influent 60% Soil trench Septic tank 1st Unit Septic tank Soil trench 2nd Unit Effluent (Reuse) Plastic sheet Soil for treatment Plastic sheet Gravel Trench pipe Gravel Effluent collection pipe Mat Air supply pipe Base soil Sand Characteristic : Energy consumption is extremely low. Construction is not needed high technique. Cost for construction and maintenance is low. The system principally has a clogging problem. Nutrient removal type soil trench system installed in Guiyang city (Sports training center) Capacity:30m 3 /day Effluent

13 Land treatment facility:multi soil layer type system JICA grass-roots roots project (NPO Green Earth Network) Influent 10.0 導水路 Sedimentation tank Capacity : 250m 3 /day Unit: m 沈殿池 Filtration tank Aeration 流量調整槽 ろ過槽 Flow equivalent tank P Multi soil layered tank 28.2( 内寸 25.4) 高度処理槽 オーバーフロー ポンプ槽 P Reuse for irrigation Effluent tank 貯留槽 P Over flow Treatment principal is almost same as the soil trench system. It was developed as a countermeasure for clogging and it is designed to treat wastewater by filtering the water through highly permeable pumice stone between soil layers 既設水路 Multi soil layer system installed in Datong City CODcr Influent 110 Effluent 18 Influent Influent Effluent Effluent

14 MSL system is used as water reuse toilet for a nature conservation area in Japan Inner condition of MSL Development of domestic wastewater treatment system for agricultural area in China Horizontal oxidation Trickling Filter Rotating Biological Contactor Combination of Lagoon and wetland Lagoon Wetland

15 Ideal Way of Technological Transfer (1) Wastewater treatment technology changes according to social conditions, and takes the most suitable form for a society that uses the technology, apart from its basic elements. Therefore, when the technology is transferred to another society, it is necessary to examine its adaptability from various aspects. Ideal Way of Technological Transfer (2) The The difficulty in transferring Japanese technology to developing countries without modification is widely known. Therefore, in order to consider future technological transfer, it is necessary to not only consider current technology but also to look into previously developed or adopted technology,, and to evaluate it from current technological or economic standpoints.

16 , , 原水ポンプ槽 散水管 散水濾床槽 散水ピット槽 2 階タンク 茨城県つくば市北中妻 E-ma il UG K11664@ nifty.c om URL ht tp://ho mepage3.nifty.com/ka nkyoukaihatu/ 5,950 スクリーン 流入 分水ピット槽 分配桝 排泥ポンプ槽 土壌式循環接触曝気槽 曝気エジェクター 担当製図承認縮尺製作訂正酒酒寄寄 1:30 図面名称 1,000 5,500 放流ポンプ槽 土壌式トレンチへ放流 GL 原水ポンプ槽 250 4,0 0 警報 OFF ON 5,950 工事名称 スクリーン 警報 OFF ON 250 1, 取手市立さくら荘浄化槽 平面図 断面図 放流ポンプ槽 土壌式トレンチへ放流 The facility installed 25 years ago: Effluent water quality is still satisfied Trickling filter Gravel contact aeration tank Influent 9,350 2, , Trickling filter 断面図 Imhoff tank(septic tank) 平面図 株式会社環境開発 Septic tank Trickling filter Gravel contact aeration tank Effluent Soil trench Ideal Way of Technological Transfer (3) Because technology is not stationary, but constantly transforms according to the situation at the site where the technology is needed, it is possible to select technology more suited to the site, and develop new technology, as required, through additional examination of technological development cases as in the Chinese case outlined this report. Moreover, locally suitable technology is selected according to the current situation of a region where the technology is adopted, but a plan adaptable to changes afterwards must be considered. In any event, previous measures for wastewater treatment were taken to solve actual problems, however, future locally suitable technology must ensure future sustainability.

17 Necessary condition for locally suitable technology Construction cost is low Percentage for labor costs is higher. Materials are cheep and possible to recruit locally. There are few machine parts. Maintenance cost is low Reduction of the electricity consumption. Reduction of the chemicals consumption. Skills are not needed for maintenance System flow is simple. Control system can be operated manually. Contribute to local material circulation and a water cycle Reuse as fertilizer/effluent reuse The basic pattern of system flow thought about locally suitable technology for small scale domestic wastewater treatment Primary treatment Simple secondary treatment Advanced treatment using natural system Effluent Sedimentation Trickling filter Multi soil layer Reuse Sludge treatment Soil trench Fertilizing (How to dry?) (Gravel)Contact aeration Constructed wetland

18 Consideration of sludge treatment is very important Typical sludge treatment of small scale plant in Japan Thickening Dewatering Dispose as waste Reuse is not premised Technology development for fertilizing is performed in a part Mobile dryer Lime Drying Process Lime Drying Process (Tochigi pref.) Sludge is dried by chemical reaction heat generated from mixing lime and water of sludge

19 Thank you for your attention See you again