| dc.description.abstract | Wastewater can be defined as any water that has been adversely affected in quality by
anthropogenic influence. It is used extensively for irrigation in Kenya, and in other countries
where water is scarce. Risks involved in re-use of wastewater have necessitated the World Health
Organisation (WHO) to formulate guidelines for irrigation water for example: total coliform
counts not to exceed lXl04 cfullOO ml for leaf crops. The study a survey evaluated levels of
contamination of the wastewater, the irrigated vegetables, and respective soils and associated
health risks. Comparison was also made between vegetables obtained from the irrigated farms
and those bought in selected market outlets. The areas covered were two urban slums located in
Nairobi, Kenya: Maili Saba and Kibera. The markets studied included: Gikomba, Wakulima,
Kibera and Korogocho. Emphasis was on bacteriology: total coliform counts and presence of
Vibrio cholera and Salmonella Typhi; and parasitology: helminth larvae and eggs, and protozoa ..
This was done using standard bacteriological and parasitological procedures. Benefits and risks
of wastewater farming (including respective awareness), as well as mitigation strategies, were
identified through focus group discussions and questionnaire survey.
Results from a questionnaire survey indicated food security aocording to the farmers: ability to
grow crops throughout the year and nutrition as important benefits that the farmers could attribute
to usage of wastewater. On the contrary, there, seemed to have been general lack of awareness
towards risks involved in usage of wastewater. Of the 232 farmers interviewed, only 28%
identified health risks as a constraint, while 22.4% were not aware of any respective risks. Most
farmers engaged in risky behaviours that could easily result in disease transmission: Eighty two
percent (190) of respondents ate sugarcane among other crops while in the wastewater-irrigated
farms, while 37.9% (88) admitted to not wearing protective clothing while working on their
farms. Thirty (30) samples taken from selected manholes and canals used for irrigation, others
taken from vegetables from farms and markets (182), soil (64) and faecal samples (174).Water
and vegetable samples were analysed for bacteriology and parasitology. The faecal and soil
samples were analysed for parasitology. Wastewater yielded average coliform counts of 1.89x107
per 100milliliters, which was statistically significantly (p<O.02) above the WHO guidelines.
Parasite larvae' (13%), Balantidium coli (86%) and Entamoeba coli (6.6%) were isolated. One
sample yielded Vibrio cholera. Kibera farm vegetables (55) also had high contamination with
faecal coliforms, averaging 3.78xl05 per 100 milliliters; and yielded parasites (64) that included:
Entamoeba hystiolytica (14%), Entamoeba coli (14%), Balantidium coli (6%). One vegetable
sample was found to have an egg of Schistosoma haematobium. There were statistically
significant differences in average contamination levels between wastewater irrigated farm
vegetables (3.78x 105 per l Ouml) and those from Gikomba (5.l8x 106 per l Oflml), Wakulima
(4.0xl06 per lOuml) and Korogocho (5.2xl08 per lOurnl) markets (p=O.OOO,p=O.OOl and
p=O.OOO,respectively). Soil contamination was at an average of 46 parasitic larvae per kilogram,
and 12.5 Ascaris lumbricoides eggs per gram. Comparing faecal analyses, wastewater farmers
were shown to contain higher intensity of parasite infestation compared to the non wastewater
users. Faecal sample results of the wastewater farming community (149) showed Trichuris
trichura (18%); Ancylostoma (24%); Strongyloides (2%); Ascaris lumbricoides (16%);
Entamoeba coli (14%); and Entamoeba hystiolytica (1.3%). One faecal sample showed eggs of
Schistosoma mansoni. On the other hand, from the 24 faecal samples from non-wastewater
farming community, Trichuris trichura was isolated (8%); Ancylostoma (41%); and Ascaris
lumbricoides (12.5%). The Maili Saba men (n=51) had a higher variety of parasitic infestations
Trichuris trichura (13.7%), Strongyloides (2%), Entamoeba coli (17.6%), Anchylostoma spp
(15.6%), Entamoeba hystiolytica (4%) and Ascaris lumbricoides (13.7%). One case of
Schistosoma mansoni was noted in a boy, compared to their counterparts, the Kibera Men (n= 10)
(Anchylostoma spp (10%), Ascaris lumbricoides (40%) and Entamoeba coli (20%)). There was
no significant difference between parasite infestation rates in the women in the two study sites.
This study has shown that, while there are benefits to wastewater farming in Kenya, there are also
risks involved. These are indicated by the parasite burden found in wastewater users, as
compared to the non-users. The isolation of Vibrio cholerae organisms from wastewater
highlights the risk of wastewater as a source of these pathogenic organisms for humans. The total
coliform count in wastewater was not only higher than the recommended level WHO, but also an
indicator that the farmers were using almost raw sewage for irrigation. This study also indicated
lack of awareness among the wastewater users, with regard to the respective risks. Thus,
awareness campaigns need to be initiated so as to educate the farmers on how to safeguard
themselves. The observation that market vegetable coliform counts were higher than farm
vegetable ones has introduced another aspect of vegetable contamination; one that originates
from the vegetable handlers: the middle-people and traders. Consumers are, therefore, advised to
cook there vegetables well before eating. Domestication of the WHO guidelines to the Kenyan
scenario and their enforcement is highly recommended. | en |
