"The chemical has been distributed to all three municipalities of Dar es Salaam and should be applied in wells three times a day," Deogratius Mutasiwa, the Dar es Salaam City Medical Officer, told IRIN.
He said chlorine had no side effects; it was also being used to purify piped water.
Mutasiwa said health centres in the city had continued to record new cholera cases although the rate had declined significantly, with a daily average of 17 since the beginning of December.
"Compared to the past, there is some improvement," he said. "In October, we had an average of 50 cases a day."
Cholera, a severe diarrhoeal disease caused by infection of the small intestine of humans with vibrio cholerae bacteria, has frequently broken out in the past three decades in Dar es Salaam and other parts of the East African country.
Health officials say cholera is transmitted via the faecal-oral route and blame its almost endemic prevalence in the country on poor public hygiene and the lack of individual precautions such as boiling drinking water.
In November, Prime Minister Edward Lowassa gave Dar es Salaam regional authorities two weeks to curb the spread of the disease or lose their jobs. The deadline expired on 3 December without anyone being dismissed.
Dar es Salaam Regional Commissioner Abbas Kandoro said from 12 December 2005 to 20 November 2006 11,227 people had contracted cholera in the region, 117 of whom had died.
Kandoro said health officials would undertake strict surveillance of the city's restaurants, hotels and bars as part of ongoing efforts to check the disease.
Moreover, he said, cultivation of vegetables within city limits, where farmers used suspected toxic water, would be banned. There were reports that vegetables were being planted in conduits for domestic sewers and industrial effluent that is discharged into the Indian Ocean. In 2004, researchers from the Tanzania National Environmental Management Council reported widespread deposits of fresh faeces along the Msimbazi Valley, a popular source of green vegetables.
Hotel and restaurant owners say city health officers have stepped up inspections and those violating hygienic rules were being prosecuted.
"If they find you violating health rules you will be prosecuted and on conviction you end up in jail. There is no option of a fine," Athanas Njau, a supervisor at Golfing Restaurant, told IRIN.
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This article was produced by IRIN News while it was part of the United Nations Office for the Coordination of Humanitarian Affairs. Please send queries on copyright or liability to the UN. For more information: https://shop.un.org/rights-permissions