Current situation Village Wastewater Issues

Review and Recommendations for Reduction of Nitrogen Export to the Coral Coast of Fiji 10

4. Village Wastewater Issues

4.1 Current situation

Villages along the Coral Coast rely on individual sewage disposal systems to treat household wastewaters. A combination of site factors, economics and infrastructure present challenges for treating household wastewater to levels that protect sanitation and reduce nitrogen loading to the coastal waters. These include: • Dwelling units that are clustered together along the shoreline with little adjacent land available for individual sewage disposal systems. Many dwelling units are within 5 m of the shoreline and are 5–10 m from neighbouring houses or outbuildings. Figure 4: Village houses and associated latrines circled crowded along the lagoon shoreline within ~10 m of beach high tide level. Photo: Chris Tanner. • Onsite disposal designs often lack septic tanks. Septic tanks have been a standard feature of onsite wastewater disposal in the U.S., Europe and Review and Recommendations for Reduction of Nitrogen Export to the Coral Coast of Fiji 11 Australasia since the 1950’s. They serve to settle solids, and anaerobically degrade and mineralise organic matter before disposal via soak-away pits cesspools or more commonly soil absorption fields. Properly managed septic tanks with periodic septage removal increase the longevity of cesspits and soil absorption systems. Without septic tanks, wastewater disposal systems are prone to clogging, backup and surfacing of untreated wastewater. As well as a practical nuisance, this can result in exposure of people and domestic animals to pathogen-infected wastewater with serious human health risks. In Fiji villages, septic tanks appear to be a relatively uncommon technology, and villagers lack information on their value and design specifications. We observed only one septic tank concrete in the village we visited Tagaqe. Environmental health officials in Fiji are working to increase the use of septic tanks in villages and have included a demonstration septic tank as a part of the onsite wastewater education project that is underway at the Fiji School of Medicine Environmental Health School in Suva. It is important to ensure that systems promoted through this project are good examples of design, construction and management practices for Fiji conditions. Effluent filters have proved to be a cost-effective means of substantially reducing suspended solids carry-over from septic tanks, and protecting the infiltration capacity of soil absorption fields and should be considered for inclusion in this demonstration project. Figure 5: Demonstration two-chamber septic tank being constructed at the Fiji School of Medicine Environmental Health School in Suva May 2004. One of the key issues with on-site fabrication of septic tanks is achieving a watertight chamber, so as to Review and Recommendations for Reduction of Nitrogen Export to the Coral Coast of Fiji 12 avoid seepage losses direct to groundwater. Corners, joints and pipe entry and exit points are potential problem areas. Photo: Chris Tanner. Figure 6: Village water garden receiving bathroom and laundry greywater from a cluster of surrounding houses. Photo: Chris Tanner. • Households are large and contain more than 5 persons per dwelling unit. The nutrient loading to an individual house wastewater disposal system will be almost twice as high as in the U.S. • Villages are rapidly converting from pit privies to flush toilets leading to soak-away pits. With the advent of public water systems, there is an active campaign by the government to encourage flush toilets, which use substantially more 12-40 L, average ~15 L per flush carriage water than “ pour flush water-seal” toilets 2 L per flush; Water Supply and Sanitation Collaborative Council, Geneva, Switzerland, www.wssc.org . Although both designs dispose wastewater directly into a soil pit, the increased carriage water of flush toilets will markedly increase the rate of wastewater flow through the soil. Flush toilets and soak-away pits can generate plumes of nutrient and pathogen rich effluent that move rapidly through sandy soil to coastal waters. The flush toilets are favoured because their convenience assures better Review and Recommendations for Reduction of Nitrogen Export to the Coral Coast of Fiji 13 sanitation. One advantage of village wastewater practices is that only blackwater toilet wastes is normally directed toward soak-away pits. This reduces the extent of carriage water and rate of soil transmission compared to comparable Western situations. Greywater bathroom, laundry and kitchen waters contains only a small proportion of household nitrogen and pathogens and is directed to small “water gardens” directly adjacent to the home. Figure 7: Village individual household greywater treatment garden. Photo: Chris Tanner. • There is a lack of funding available to upgrade onsite wastewater treatment. Improvements to wastewater treatment are occurring in the villages through the efforts of volunteer women’s cooperative groups. These groups are installing the flush toilets connected to low-cost soak-away pits. The soak-away pits are made of perforated 40-gallon metal drums for solid settling that are surrounded by coral rock Fig. 9. These systems have low sludge storage capacity and are poorly designed for efficient septage removal. They are susceptible to clogging and overflow, and are therefore likely to have a restricted operational life and create serious health and environmental risks. Such systems provide minimal protection against groundwater contamination Review and Recommendations for Reduction of Nitrogen Export to the Coral Coast of Fiji 14 and are likely to pollute nearby beaches and lagoon waters. In comparison to these simple systems, septic tanks represent a relatively large capital investment. Figure 8: Clogged village household greywater seepage area showing ponding circled of contaminated water. Such areas pose serious risks in terms of contact and transmission of pathogens, as well as potential to generate odour and insect pest nuisances Photo: Chris Tanner. Sewering and transmitting village wastewater to a central municipal wastewater treatment plan is an unlikely option for the entire coral coast. Although the community of Sigatoka has a municipal wastewater treatment plant, sewered areas are focused within several kilometres of the plant, and progress with planned extension of the reticulated area has been very slow. Extending the sewer lines to the villages along the coral coast will be very costly to the municipality and to the village residents. Village residents could be faced with high costs for “hook-up” connection to the sewer as well as annual fees. If sewers do become available, it is not clear if individual residents would be required to connect to the sewer. In addition to constraints on village acceptance, hotels along the coral coast may have little incentive to hook up to a municipal sewercentralized treatment system. Many of the hotels Review and Recommendations for Reduction of Nitrogen Export to the Coral Coast of Fiji 15 have already constructed modern wastewater treatment systems at considerable expense and often value the wastewater as a prime source of irrigation water for their landscaping and golf courses. Planners should explore the feasibility of extending of the Sigatoka sewer to coastal villages, hotels and developments adjacent to the existing sewered areas – and to continue to encourage the return of treated wastewater for use as irrigation water for the hotels. Additional land application, via irrigation, will minimize direct wastewater discharge and reduce the risks of nutrient contamination to coastal waters. Sigatoka municipality is to be commended for incorporating land treatment into their wastewater treatment. A portion of the treated wastewater from the Sigatoka plant is currently piped to a hotel development within 5 km of the plant. Figure 9: Recently constructed, low-cost village household soakage pit awaiting connection to flush toilet system. The soakage pit comprises two perforated 200L steel drums set one above the other in a large hole, surrounded by coarse coral rock. The base of upper drum and top of lower drum are removed to create a single chamber. Photo: Chris Tanner. Review and Recommendations for Reduction of Nitrogen Export to the Coral Coast of Fiji 16 Return of nutrients to land via irrigation is an ideal disposal option providing it is done at sustainable loading rates to prevent surface runoff and minimise leaching losses Crites and Tchobanoglous, 1998; NZLTC, 2000. Hydraulic application rates and nitrogen loading rates should be checked and monitored for existing and new irrigation schemes. As a preliminary guideline for sandy coastal soils N loading rates should not be more than 100 kg N per year and application rates should probably not exceed 20-30 mm d -1 Note: these are only rough guidelines; specific local guidelines should be developed taking account of local soil characteristics and climate. Higher N loading rates of 200-300 kg N per year are likely to be possible on land managed for productive cropping or grazing Crites and Tchobanoglous, 1998; NZLTC, 2000. Suitable treatment levels and health precautions will also be required to protect farm- workers, neighbours, consumers, and livestock. Figure 10: Recently connected village household soakage pit for toilet waste disposal. The still incomplete system has been partially uncovered to show the construction method used. Coarse coral rock is visible surrounding the central perforated steel drum. Note the close proximity to the toilet building. Photo: Chris Tanner. Review and Recommendations for Reduction of Nitrogen Export to the Coral Coast of Fiji 17