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United Nations Environment Programme
Division of Technology, Industry and Economics
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Newsletter and Technical Publications
<International Source Book On Environmentally Sound Technologies
for Wastewater and Stormwater Management>

8.3.2 Large-scale technologies

Again large treatment plants service the large urban centres such as in Fiji and Guam. Treatment methods include sedimentation, trickling filters, and anaerobic and aerobic lagoons. Currently the Kinoya treatment plant, that service about 85,000 people in the Suva area, is being upgraded using extended aeration and will eventually be able to service 360,000 people. Raw sludge is digested and put into drying beds. The circular digester produces about 63m3 of sludge per day. Some of the dried sludge is used as soil conditioner and that not used is dumped into a landfill. In Guam belt presses are used to mechanically dry sludge.

In American Samoa two separate treatment plants use clarigesters for the primary treatment of wastewater. A clarigester is a clarifier that sits on top of a digester constructed as one unit (Figure 8.2). The clarigesters separate settleable solids and floating debris from the inflow of wastewater. Settleable solids sink to the digester compartment where they undergo digestion and eventually removed as sludge. Sludge is removed from the clarigesters and dewatered in covered drying beds. Supernatant from the digester compartment and drainage from the drying beds is pumped back into the plant headworks. Clarigester treated wastewater is than disinfected using chlorine and discharged into two ocean outfalls (30m and 45m deep). As shown in Photo 8.3, the plant also has the facility to except and treat septage, trucked in from septic tanks through the island.

Figure 8.2: Clarigester (lager image)

Photo 8.3: Disposal of septic tank solids into Clarigester in American Samoa

American Samoa and Guam are the only countries in the Region where treated wastewater is disinfected before discharging into the sea.

It should be noted that raw sewage which has been collected through sewer systems in Kiribati (Tarawa), Nauru, Marshall Islands (Majuro), Solomon Islands (Honiara) and PNG (parts of Port Moresby) is discharge into ocean outfalls with out treatment. Also some of the older treatment plants (Pohnpei and Chuuk) do not operate properly thus not improving influence quality much.

8.3.3 Traditional waste disposal technologies

Before the arrival of missionaries, Western ways and densely populated areas, going to the bush, the beach or the sea was the normal methods to relieve oneís self within the Region. Water was not required for flushing, paper was not required and a disposal system was not required. All that was required was a private place and that was not too hard to find. It was the outside world that introduced toilets, collection systems and treatment plants to the Region.

The closest to a Regional "small scale" traditional disposal technology would be the over water (overhung) latrines (also as known as "benjos" in FSM as described in Case Study 1). These are "latrines" that are constructed over a body of water into which excreta drops directly as shown in Figure 8.3. They are cheap and easy to construct no water or paper was required, easy to clean and maintain and some had a great view. Also they were communal in nature (ie several people could use them at same time) and thus presented the opportunity to catch up on the latest gossip. What else could you ask for? However with growing populations resulting in larger discharges and pressure on marine food resources, the risk of pollution and disease also increased. The tourist industry also frowned on them lining the beaches. Over water latrines are now history however that are still use in some parts of the Region.

Figure 8.3: Overhung latrines

In rural coastal areas throughout the Region the over water latrine still has potential to provide an important service to the community. Under favourable conditions and good management practices the over water latrines will still be part of the Regionís waste disposal seen.

8.3.4 Regional technologies

As seen from above the current wastewater treatment technologies used in the Region range from none to secondary treatment with no one method standing out as the one to use. Without performance monitoring data available, it would still be fair to conclude that many of the existing treatment plants and methods are not working, as they should. The problem may be that the systems are old, expensive to maintain, operate and to replace. The utilities do not have the resources to adequately provide an environmentally friendly service to its customers and the customers cannot afford to pay for an adequate service. Therefore service deteriorates and the environment suffers.

As concluded from the SOPAC workshop on Appropriate and Affordable Sanitation for Small Islands, for a sanitation project to be understood, accepted and used, the community must support and be involved with the projectís development. Public education and awareness is needed so that the community can see the benefits of both improved health and environment brought about through improved wastewater disposal facilities.

 

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