Zanzibar’s waste management and sanitation facilities have not be able to cope with the increase in the Tanzanian island’s population, which grew from 300,000 in 1964 to 1.1 million people now.
Only a minority of residents in Zanzibar City are connected to the sewerage network, which consists of a mere 25km of pipes. The rest of the island’s inhabitants rely on septic tanks and soak pits, while some people have no toilets at all.
A 2006 government directive requires hotels to treat their own sewage, but this rule is widely flouted.
Considerable amounts of sewage, including from septic tanks where only minimal treatment takes place, are discharged directly into the sea: The island has no sewage treatment plant.
“Primary liquid waste treatment is only done at the septic tank where there is only [a] 30 percent reduction of the BOD [biological oxygen demand - a measure of water quality] before being discharged into the ocean along any of the 27 sea outfalls,” Mzee Juma, a ZMC sanitary engineer, told IRIN.
Sludge from septic pits and latrines is dumped into the mangrove stands and pollutes the sea.
Contamination has already been noted in the Maruhubi area, north of Zanzibar City, according to a government report prepared for the WIO-LaB project, coordinated by the UN Environment Programme and the Global Environment Facility.
Maruhubi is used by private sludge emptiers and is prone to flooding during high tides. Mangroves growing there help absorb some of the organic waste.
Studies have shown that nutrient levels in near-shore waters are higher than normal for tropical seawaters, indicating anthropogenic inputs. Faecal and total coliform levels of up to 70/100ml and numerous thousands per ml of seawater, respectively, have been reported in the waters fronting the Zanzibar Municipality, said the WIO-LaB report. [...] “Contamination of biota [plant and animal life], including those harvested for food such as bivalves [kind of mollusc], has been reported, as have water-borne diseases such as dysentery, diarrhoea, cholera and typhoid, among others,” it said.
Untreated municipal and industrial wastes are currently the main threats to the quality of water, while overflowing pit latrines compound the pollution problem.
There is an urgent need to install a sewage treatment facility and intercepting sewers along the coastline. Other options include the construction of longer sea outfalls to the deep sea.
Solid waste management is also inadequate. Of about 200 tons generated daily, only 45 percent is moved to dumping sites, with the remainder left in open spaces. About 0.5kg of solid waste is generated per capita per day – 80 percent of it organic – according to estimates.
Source: IRIN, 23 Apr 2010