Evaluation Of The Efficiency Of Wastewater Stabilization System Using Macro-Invertebrates Community And Pollution Tollerance Index

The development and application of bioindicators has been in use since 1960s (Hilsenhoff, 1988). Bioindicators are developed for ecosystem health assessment, for human effects and interventions, human health assessment, and for evaluating sustainability (Burger, 2006). Bioindicators are recommended for water quality assessment as they are less costly and environmentally friendly biomonitoring tool (Aura et al., 2010). Biomonitoring of ecosystems require the use of bioindicators that are biologically and methodologically user friendly, and can effectively be used to provide early warnings (Burger, 2006). Focus is now being directed towards aquatic organisms, which are used as ecological indicators (bioindicators) of water quality (Wenn, 2008). Among the most commonly used bioindicators for assessing water quality status include macro-invertebrate communities. Macroinvertebrates are commonly used to monitor the health status of different watersheds (Holt, 2010). Unlike chemical analysis that gives snapshot status, macro-invertebrates provide cumulative effects of long term status of watersheds (Andem et al., 2015). Macro-invertebrates populations have families Abstract: In this study, macro-invertebrates community was used to establish the pollution tolerance index of four wastewater stabilization ponds at University of Eldoret in Kenya. The stabilization ponds have not been expanded since the inception of the university despite the ever rising population of students and staff. As such this study was set to evaluate the efficiency of the wastewater stabilization ponds in wastewater restoration by the use of bioindicators. Since chemical analysis is expensive and hazardous to human health, index of benthic integrity that uses macro-invertebrates communities was used in the study. Macro-invertebrates were sampled from one identified site of each of the four wastewater stabilization ponds monthly for a period of six months. Macro-invertebrates samples were placed in plastic containers and preserved in 70 % alcohol, which were taken to the laboratory for identification. Five orders comprising thirteen Families were collected during the study period. The abundance by percentage occurrence was Diptera (59%), Hemiptera (38%), Coleoptera (1.5%) Ephemeroptera, (1%), and Isopoda (0.5%). The number of taxa increased from pond 1 to pond 4. Pond 1 was least diversified with seven families while pond 4 was most diverse pond with 10 families. Pond 2 had eight families while pond 3 had nine families. The heterogeneity indices revealed high values of diversity and evenness in the stabilization ponds except in pond 1; (0.4255) and (0.3826) respectively, while in the contrary dominance was highest in pond 1 (0.7546). Results for Pollution tolerance index value showered poor water quality with range of values from 7.7 to 11 an indication of inefficiency of the wastewater stabilization system.