1. Overview and Key Points
In order to eliminate the common ‘out of sight out of mind approach’ in sanitation, whereby sewers and/or drains are discharged into rivers, a Decentralized Wastewater Treatment System (DEWATS) was designed and implemented in Kieu Ky to treat wastewaters arising residential properties and various craft industries. A clear understanding of topography, population densities, land availability and prior surveys regarding people’s needs was seen to be key in planning this system which has ultimately rendered positive results in its pilot stage.
- Decentralized wastewater treatment system (DEWATS) designed for domestic and industry wastewater.
- Existing and available resources in the city were taken full advantage of increasing sustainability
- User fees sufficed to cover operation costs and short/medium term maintenance costs.
- People’s committees formed in order to ensure community involvement through Community Based Organisations (CBOs) during all stages of the project.
Kieu Ky, located in the Gia Lam district of Hanoi (Viet Nam) is a peri-urban area consisting of densely populated village clusters located at a considerable distance from one another, each of about 15,000 inhabitants per sq km. Positioned only 20 km from the urban centre, Kieu Ky follows a similar economic growth pattern to the big cities. Alongside this progress however, the area has suffered a number of setbacks. One of these concerns sanitation services. Despite there being 97% latrine coverage in Kieu Ky in 20061, only 25% of these were confirmed to follow the Ministry of Health regulations and standards. Greywater from these latrines was directly discharged into the environment having a direct impact on rivers contaminating waters to the extent of killing fish and creating skin allergies among residents. In addition to this, the untreated wastewater was discharged into rice fields via irrigation canals. The risk to public health as well as the environment was further accentuated by effluents from the nearby urban centre flowing downstream into Kieu Ky. Centralised sanitation services do not extend fully outside city centres, and as a consequence public urban services expected Kieu Ky’s resident’s to dispose of their wastewater by themselves. These current practices were a threat to general public health and posed risks for those who worked in rice fields where all this wastewater was drained.
3. Project planning and design
In order to overcome this, a pilot project was designed in 2007 for 60 households in Kieu Ky with the aim of improving and upscaling the on-site sanitation approach based on septic tanks. This new model was to identify an appropriate collection and treatment system for this peri-urban area assessing it’s scope for replication.
Consequently a pilot project was initiated through a number of surveys which discussed technical, institutional and financial models for the treatment of wastewater from both the craft industry as well as domestic wastewater. This was undertaken in order to determine the current sanitary and technical situation as well as to enable the identification of where the lack in current resources lays.
Following a number of public consultations, it was decided that a DEWAT facility with a piped system be connected to the septic tanks already present in most of the households. The construction phase began in November 2008 and was ongoing till February 2009 during which the treatment installation, piped system and treatment devices were installed.
4. Technology option
Based on a number of factors such as availability of land, composition of wastewater, availability of funds and expertise, a choice was made favoring a three component based system composed of a Baffle Anaerobic Septic Tank (BAST), Aerobic Filters (AF) and Constructed Wetlands (CW). Each of the system components proposed played a significant role in the wastewater treatment process.
Since most households already discharged their wastewater into septic tanks, these were used as pre-treatment tools allowing for the settling of gross solids before the overflow from the septic tanks is piped into the BAST. Using baffles to force the wastewater to flow under and over them, these tanks allow for greater contact between wastewater and the sludge blanket resulting in increased anaerobic degradation of suspended and dissolved organic pollutants.
Once the wastewater leaves these tanks, it is directed towards AF which in turn allows wastewater to flow trapping particles and organic matter which is then degraded by the biomass layers attached to these filter material. Lastly, the wastewater is drained into a CW enabling additional treatment such as the reduction of nitrogen compounds and removal of heavy metals and pathogens. The treated wastewater can then be discharged into either sewers collecting water for irrigation or directed towards natural water bodies.
5. Institutional and management arrangements
Design and project management were undertaken by Eau Agriculture Sante en Milleu Tropical (EAST Vietnam) and The Bremen Overseas Research and Development Association (BORDA). These two NGOs were responsible for agreeing on how to identify and choose a suitable construction company to undertake the implementation of the proposed DEWATS. They were also jointly responsible for establishing and proposing a financing and operational mechanism for the operation and management of the package treatment plant.
In peri-urban areas such as Kieu Ky, the management of wastewater is carried out by communities. For the pilot phase of this DEWATS, a variety of local stakeholders were involved, namely the managers of the system known as the People’s Committee of the community (PCc), local organizations as well as operators. The PCc was responsible for providing administrative support and local authority to local organizations.
These organizations were composed of a group of Community Based Organizations (CBOs), women groups, village authorities, which were mainly in charge of collecting fees, managing the accounts, setting up contracts with sanitation companies for sludge removal or filter material wash, and motivating residents towards adopting clean sanitation infrastructure.
In addition to this, these local organizations monitored part time operators whose responsibility it was, to carry out small technical maintenance works as well as report back to local organizations when any major tasks needed to be carried out.
6. Financing arrangements
The projects material and construction costs amounted to US$ 31,000 which was financed by the Asian Development Bank (US$10,000), Institute des Metiers de la Ville (IMV) (US$7,000) and BORDA (US$14,000).
As for maintenance and operation costs, following a willingness to pay (WTP) survey a fixed monthly fee of VND 5000 (US$ 0.30) per household was settled. This sufficed for an operators wage as well as short and mid-term maintenance fees (sludge removal, replacement filters media etc).
7. Project outcomes and impacts
Initial monitoring indicated that the facility successfully removed up to 98% of biochemical oxygen demand and 96% of chemical oxygen demand, therefore the success of the pilot project in connecting 60 households to the sanitation system was remarkable and as a consequence more households indicated an interest to be connected as well as to pay for the sanitation services. It must be recognised however that during the construction phase, technical difficulties were faced especially when connecting households due to land topography since this system was entirely gravity-fed. This was mainly the case where discharging outlets of particular household septic tanks were too low to be connected to the designed piped system. As a result, following the installation of the DEWATS facility, original storm water drains were still used to discharge wastewater from some households.
During the time of construction, no inconveniences were reported by residents. This was linked to good involvement of local supervisors and construction managers.
8. Overall sustainability of system
This pilot project demonstrates an appropriate use of resources. Similar to other peri-urban areas in Vietnam, land prices in Kieu Ky are increasing due to the decreasing availability of land. Consequently a combination of intensive technologies was selected in order to maximise wastewater treatment in the minimum amount of space possible. This was undertaken in a decentralized manner, since the area is composed of various clusters of population making DEWATS an appropriate choice. Furthermore, existing infrastructure such as septic tanks were taken advantage of as a pre treatment facility thereby ensuring a more sustainable wastewater flow into pipes reducing the maintenance requirement of pipes and increasing the efficacy of the component system proposed. However it must be noted that due to
An important factor to note is that no energy input was required for transporting wastewater from households to the treatment facilities; a gravity fed system was designed avoiding the use of pumping stations adding to the environmental sustainability of the system. When considering maintenance and operation, the model followed a community based approach where local organizations are involved with carrying out all tasks with the help of an operator. This engagement with communities proved to be an increasingly important component of the sustainability of this project.
9. Lessons learned
- Decentralization and user involvement
Decentralized systems are designed to operate locally and thus local context must be defined accurately by the community itself in order to ensure that demands are being met. This is achieved through awareness raising activities where open dialogue is encouraged in order to exchange ideas and opinions.
- Movement towards a collective system
WTP studies have shown that people would preferably pay for a collective service and cover operation and maintenance requirements for these than for an individual system. The system implemented in Kieu Ky, based on combined wastewater treatment facilities and a shared piped network reflects a collective system and thus, surveys showed that residents WTP for operation and maintenance stood at VND 9000 (US$0.5), VND 2000 more than what the pilot project set for household monthly payments.
- Reducing costs by maximising use of existing infrastructure
In order to control the flow during rainy spells and avoid solid waste from entering into drains, simple hydraulic systems could be added to the existing infrastructure rather than designing entirely new systems for urban environments. In the case of Kieu Ky, the alternative to the newly built piped network could have been the installation of grids over existing drains in order to filter out solid waste. Not only would this save on project costs, but would also be less time-consuming and energy intensive.
- Need for regulation in peri-urban areas
As a whole, peri-urban areas lack policies and/or national targets pertaining to the sanitation sector. As a consequence, wastewater is not regulated; this is therefore a big determent towards the instigation of sustainable sanitation practices.
Specific design requirements
When considering new sanitation systems, where residents already own disposal facilities (individual septic tanks in the case of Kieu Ky) each with their own dimensions, positioning and capacities, consideration needs to be given to each of these existing household facilities separately, in order to appropriately design their connection to the new system.