TITLE:
Multicriteria Assessment of Various Onsite Wastewater Treatment Options for Nigeria
AUTHORS:
Chidozie Charles Nnaji, Chinedu Ekechukwu, Fortune Onyia, Christopher Afangideh
KEYWORDS:
Septic Tank; Wastewater; Contamination; Analytic Network Process; Risks
JOURNAL NAME:
Journal of Environmental Protection,
Vol.5 No.2,
February
28,
2014
ABSTRACT: Eight onsite wastewater treatment
systems (OWTS) were evaluated for suitability of application in Nigeria for
efficient treatment and disposal of domestic wastewater, using analytic network
process (ANP). Ten location related risks were used as criteria in the decision
making process. Expert views were used to obtain pairwise comparison matrices
of the OWTSs with respect to the criteria. Saaty’s Super Decision Software was
used to complete the ranking process. The order of ranking obtained was as
follows: septic tank with absorption field (0.1502) > septic tank with
soakaway (0.142) > composting toilet (0.128) > septic tank with sand
filter (0.125) > septic tank with constructed wetland (0.12) > septic
tank with holding tank (0.12) > septic tank with mound system (0.118) >
septic tank with recirculating sand filter (0.096). However, when the costs and
life spans of these systems were incorporated into the ranks, and considering
other factors, the septic tank with absorption field stood out as the best
option. A simple sensitivity analysis shows that depth to water table,
proximity to drinking water, susceptibility to flooding and proximity to large
roots have the highest influence on the ranks of OWTSs.