EFFECTS OF BIOREMEDIATION ON PHYSICOCHEMICAL PROPERTIES AND HEAVY METAL CONTENT OF GROUNDWATER CONTAMINATED WITH DIESEL USING MIXED CULTURE MICROORGANISMS

Abstract

Bioremediation of groundwater contaminated with diesel by a mixed culture of microorganisms was investigated. The results obtained showed that the microorganisms; total heterotrophic bacteria (THB), total hydrocarbon utilizing bacteria (THUB) and total fungi (TF) had a positive response in utilizing total petroleum hydrocarbon (TPH) as diesel. The order of hydrocarbon utilization was: THUB>TC>THB with mean growth rate constants of 5.95x10⁻³ hour⁻¹, 3.97x10⁻³ hour⁻¹ and 2.98x10⁻³ hour⁻¹ respectively. A total of 10 bacterial isolates were recovered from the total viable count (TVC) plate, of which 6 were hydrocarbon degraders. The genera of the indigenous bacteria identified were: Bacillus spp., Pseudomonas spp., Corynebacterium spp., Flavobacterium spp., Alcaligens spp., Aeromonas spp., Cellulomonas spp., Chromobacterium spp., Serratia spp., and Proteus spp. The four fungal isolates obtained included: Candida spp., Aspergillus spp., Detorula spp. and Tricoderma spp. Notable bioremediation markers: chemical oxygen demand (COD) were significantly reduced by 97.98%; biochemical oxygen demand at day-5 (BOD5) by 7.58 %; TPH as diesel by 91.50% and alkalinity increased by 163.64%. In conclusion, while there were appreciable improvements in some physiochemical properties and found within the W.H.O Standard, others needed post-treatment to make the groundwater safe for domestic and agricultural uses.