Constructed Wetland for a Peri-Urban Housing Area Bayawan City, Philippines
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Case study of sustainable sanitation projects Constructed wetland for a peri-urban housing area Bayawan City, Philippines biow aste faeces/manure urine greywater rainwater Pour-flush toilets (to septic tank) Small-bore sewer system collection Septic tank effluent treated in constructed wetland treatment Treated wastewater for irrigation reuse Fig. 1: Project location Fig. 2: Applied sanitation components in this project 1 General data 2 Objective and motivation of the project The objectives of the project were to : Type of project: • Protect coastal waters from pollution with domestic Peri-urban upgrading of a settlement; domestic wastewater. wastewater treatment with constructed wetland (or reed • Protect the health of the local residents through improved bed) housing with safe sanitation and wastewater treatment facilities. Project period: • Demonstrate constructed wetland technology. Bayawan Start of planning: Feb 2005 was the first city in the Philippines that built a constructed Start of construction: June 2005 wetland for domestic wastewater treatment. Therefore, Start of operation: Sept 2006 (and ongoing) one of the objectives was to use it as a pilot and Project scale: demonstration project for other communities. Relocation housing area for 676 houses (average household size of 5 people, although some houses contain more than one family); design figure: 3380 people. 3 Location and conditions Total construction cost for the constructed wetland was Bayawan City is located in the south-west of Negros Island, about EUR 160,000 including consultancy and labour. covering a total land area of about 70,000 hectares and with Address of project location: a population of about 113,000. The project is located in a Fishermen’s Gawad Kalinga Village, Barangay Villareal, peri-urban area of Bayawan, which has been used to resettle Bayawan City, Philippines families that lived along the coast in informal settlements and had no access to safe water supply and sanitation facilities. Planning institution: Records from the City Health Office showed a high incidence City of Bayawan, Philippines of morbidity and mortality arising from water-borne diseases Oekotec GmbH, Belzig, Germany in these informal settlements. Gerry F. Parco & Marc Mulingbayan, Philippines Executing institution: City of Bayawan, City Engineering Office Supporting agency: Department of the Interior and Local Government (DILG)- GTZ Water & Sanitation Program (but only for consultancy fees and various technical assistance - not for construction itself which was financed by Bayawan City) Fig. 3: Relocation housing area, Barangay 1 Villareal, Bayawan City, June 2006 (source: Bayawan City). The families have been resettled to a 7.4 hectares social housing site which consists of 676 terraced houses, a day- 1 A barangay is the smallest administrative division in the Philippines. 1 Last updated: 22 Jan. 2010 Case study of sustainable sanitation projects Constructed wetland for a peri-urban housing area Bayawan City, Philippines care centre, a health centre, a multi-purpose hall and a the general decision to treat the wastewater in a community centre. By December 2008, 555 of the houses decentralised facility and not only in septic tanks. were occupied (and by September 2009, all 676 houses were occupied). The majority of the households that moved A German consultant (Dr. Joachim Niklas, Oekotec GmbH) into the relocation area make their living from fishing. The visited Bayawan twice during the construction phase, in average household size is 5 people, but it has to be November 2005 and June 2006. The first visit included the mentioned that some of the houses contain more than one selection of a filter material for the soil filters. A manual for family. operation and maintenance was developed together with local consultants and the City Engineering Office. The One of the projects recently introduced in the Fishermen’s second visit took place when the distribution pipe system Gawad Kalinga Village to diversify their livelihoods, is was installed in the vertical soil filter. vegetable and cut flower production using organic farming methods. The construction was carried out by the City Engineering office from May 2005 to August 2006. The constructed The under-five child mortality rate 2 in the Philippines is wetland was inaugurated in September 2006 and has been currently approx. 28 children per 1000 which is relatively low in operation ever since. The GTZ sanitation program in the for a developing country Philippines came to an end in March 2009, and the (http://www.childinfo.org/mortality.html ). constructed wetland now continues to be operated by Bayawan City Council. 4 Project history The implementation phase included social preparation activities for the future inhabitants of the relocation area. As The concept of ecological sanitation was first introduced to part of the relocation project the City of Bayawan set up a the Visayas and Mindanao Regions of the Philippines during village association to organise the affairs of the relocation the “1st International Symposium on Low Cost Technology area. Options for Water Supply and Sanitation” in September 2004 in Bohol (speakers and guests came from Philippines, The planning process was a joint undertaking of one German Indonesia and Germany). The conference was organised by and two Filipino Consultants, supporting knowledge the DILG 3-GTZ Water & Sanitation Program and the WSP exchange and the introduction of a technology which was (Water & Sanitation Program) of the World Bank. relatively unknown in the Philippines: the constructed wetland (also called: vegetated vertical soil filter or reed bed). Representatives from the City of Bayawan attended the symposium and a group of German and Filipino experts 5 Technologies applied subsequently visited Bayawan City to conduct a rapid assessment of the sanitary situation in specific areas. Two wastewater management and sanitation options were The houses in the resettled fishermen’s village have pour- identified: a constructed wetland for domestic wastewater of flush toilets. The wastewater from the toilets, bathrooms and a peri-urban resettlement area (described in this case study) kitchen sinks is partially treated in septic tanks where solids and a dry sanitation concept (urine diversion dehydration are settled and the organic load is reduced 4. There are a total toilets) for the sparsely populated rural areas (as described in of 67 septic tanks, each receiving the wastewater from 6 to a separate SuSanA case study). 10 houses. The liquid portion of the wastewater (overflow from septic tanks) is transported through a small-bore sewer The first visit of the German and Filipino consultants was in system with a 250 mm diameter pipe sloped at 0.2% towards March 2005. The experts assessed the location and design the main sump for storage and additional solids removal. parameters and discussed different technical options with the engineers and officials of the local government of Bayawan From the main sump, the wastewater (septic tank effluent) is City. The detailed design was prepared by Filipino pumped into four header tanks and then flows by gravity into consultants and the construction process was carried out by the first cell of the constructed wetland, which is a vertical the City Engineers Office of Bayawan. The Filipino soil filter. From here, the wastewater flows by gravity into the consultants were also responsible for construction second cell. This cell is a horizontal soil filter. The effluent supervision. from the second cell is collected in the effluent sump. In April 2005, the partnership between the City Government The faecal sludge from the septic tanks will be treated in of Bayawan and the GTZ was formally sealed with a drying beds that are located at the sanitary landfill. Emptying Memorandum of Agreement providing technical assistance in of the septic tanks has not yet been necessary, but is the construction of the constructed wetland treatment facility. expected to be carried out in 2009. The drying beds will be ready for operation soon after Sept. 2009 5. The users were not consulted in the design of the system, only the city government with its various offices, i.e. health, engineering and environment. But the users were involved in 4 Bayawan City had started with the construction of the septic tanks before the idea of the wetland was conceived. They are designed as 3-chamber tanks. 2 The under-five mortality rate is the probability (expressed as a rate 5 Jouke Boorsma on 2 Sept. 2009: “ The septic treatment system is per 1,000 live births) of a child born in a specified year dying before almost operational. As of now, we are waiting for the waterproofing reaching the age of five if subject to current age-specific mortality to be applied in the storage tanks. At one of the beds we applied rates. concrete tiles. If it will give us a positive result, we will apply it on the 3 DILG is Department of the Interior and Local Government. other beds as well .” For photos see link in Section 13. 2 Last updated: 22 Jan. 2010 Case study of sustainable sanitation projects Constructed wetland for a peri-urban housing area Bayawan City, Philippines The treated wastewater is pumped from the effluent sump people (600 one-family houses 6 with on average 5 people into an elevated storage tank and is used for irrigation mainly per household) and a BOD concentration of 300 mg/l. At the in the cut flower and vegetable farming project of the GK last count, 555 houses were occupied (December 2008) 7. Fishermen’s Village. This would result in a wastewater flowrate of 140 m3/d and BOD load of 42 kg/d. To this date, the actual flowrate has not The combination of septic tanks, small-bore sewers and been measured. constructed wetland was built because the construction of the houses in the relocation area was already in progress The actual BOD concentration in the influent was determined when the City of Bayawan decided to upgrade the treatment to be 138 mg/L in a study in Oct.