A Thesis on: Constructed Wetlands for Greywater Treatment: The Case of Spa Service Enterprise
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Date
2011-06
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Addis Ababauniversity
Abstract
Wetlands have long played a significant role as natural purification systems, and have been
effectively used to treat domestic, agricultural and industrial wastewater. However, very little
has been done on the use of constructed wetlands as treatment option for greywater especially in
Ethiopia. Six experimental CW cells have been designed and constructed in order to evaluate the
performance of constructed wetland and generate information about the effects of substrates
(gravel, sand and scoria) and substrate-plant combination, by planting two types of plants
(V.anagallis-aquatica and C.bengahllnsis). In addition the two plants were immersed in grey
water for about a day in order to evaluate if any significant removal efficiency is shown. A total
of 27 samples were collected and analyzed for selected wastewater quality parameters.
Comparing the removal efficiencies of the three substrates without plantation, the highest scores
were achieved by cells containing sand and scoria. The sand cell showed the best performances
for orthophosphate (67.54%) and BOD5 (74.64%), and the scoria cell showed highest removal
for Na (66.6%) and COD (61.1%). The only parameter that showed to be statistically significant
(p<0.05) were sodium removal in the scoria cell. In the case where the cells were planted with
V.anagallis-aquatica the sand performance for orthophosphate (72.89%) and BOD5 (76.87%),
the scoria achievement for COD (59.86%) and sodium (60.51%), and the gravel cell score for
NO3-N (65.38%) and Mg (29.3%) were the highest for each parameters. On the hand of
substrates that were plated with C.bengahllensis the cells with scoria media showed best results
for Na (56.39%), COD (53.19%), and BOD5 (66.88%); the sand cell performed highest for
orthophosphate (75.55%) and NO3 (82%); and the gravel cell the first of the three in removal of
Mg (29.3%). Finally, from the two plants, which were immersed in greywater in two separate
bottles, V.anagallis-aquatica showed the better efficiencies for orthophosphate (43.99%), COD
(36.36%) and Mg(88.9%). All of the results showed not to be statistically significant (p<0.05).
Generally, it can be concluded the study implicated the potential use of CW as an alternative
system for greywater treatment
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Keywords
Greywater Treatment