IMPACT OF TANNERY EFFLUENTS ON THE QUALITY OF ENVIRONMENTAL SAMPLES AND BIOREMEDIATION POTENTIALS OF MICROBIAL ISOLATES
IMPACT OF TANNERY EFFLUENTS ON THE QUALITY OF ENVIRONMENTAL SAMPLES AND BIOREMEDIATION POTENTIALS OF MICROBIAL ISOLATES
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Date
2014-04
Authors
TIJJANI, MUHAMMAD BASHIR
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Abstract
Impact of tannery effluents in the environment and bioremediation potentials of microbial isolates were evaluated using different methods. Physico–chemical properties of the effluent samples vary in each tannery with higher mean values in Tan A followed by Tan C and then Tan B, indicating higher pollution level in the order Tan A < Tan C < Tan B. Similarly, these properties in well water samples studied fluctuate. Significant differences were observed in mean TDS, DO and BOD values. Seasonal variation in the mean physico-chemical properties of well water samples using students’ t-test showed significant differences, where higher TSS and BOD were recorded in the dry season while DO was considerably low in the dry season. The mean Cr (4.85mg/L) concentration was significantly higher (P ≤ 0.05) in effluent sample compared to the well water samples. It was established that the level of chromium (Cr) were significantly higher (P ≤ 0.05) in effluent analyzed from Tan A (5.29mg/L) then Tan B (4.91mg/L) and the level was lower in Tan C (4.36mg/L). Statistical analyses of heavy metal content in the tannery effluent from different sampling points revealed significant differences (P ≤ 0.05) among the tanneries where it shows decrease in all metal concentrations downstream. Higher concentrations of metals were recorded in the dry compared to wet season. Bacterial contamination of the well water samples were significantly higher (P ≤ 0.05) during the dry season compared to the wet season. The bacterial load was increasing with increasing distance from the pollution source regardless of the season. Comparisons of mean heterotrophic, total coliforms, fecal coliform and fungal counts in effluent samples from tanneries showed no significant differences (P > 0.05), but significant difference (P ≤ 0.05) was prominent in the fungal counts between Tan C and the other tanneries. Pseudomonas aeruginosa and Bacillus cereus subjected to assessment for resistance to Cr were selected as the candidates for bioremediation of the effluents. In the flasks containing minimal medium with 25mg/L Cr inoculated with P. aeruginosa Cr concentration declined from
25 to 20mg/L after 120hr while in the aerated vessel it declined to 19.09mg/L, in the flask and aerated vessels with B. cereus Cr level declined to 19.15mg/L and 19.9mg/L respectively after 120hr of incubation. In flasks containing effluents inoculated with P. aeruginosa, Bacillus cereus and consortium Cr declined to 18.7mg/L, 19.81mg/L and 17mg/L respectively after 120hr indicating 20.8 – 32.1% Cr removal from the effluent. Performances of P. aeruginosa and consortium in the aerated vessels were significantly higher than in the flask. Aspergillus niger, Penicillium sp and Trichoderma longibrachiatum were selected as fungal candidates for bioremediation of the effluent. The fungi and their consortium performed best at pH 6 leaving behind 36 – 39.6% Cr in the media. The Cr removal in the treated effluents by T. longibrachiatum was higher than that by A. niger and Penicillium sp. These test strains bioadsorbed 15.7mg/L, 15.0 mg/L and 14.6 mg/L Cr respectively from the effluent after 120hr treatment in the flasks on the shaker, and Cr removal in the aerated vessels were higher. Mutant A. niger (MSUV30) and Penicillium (MSUV10) were more effective than their respective wild parent strains. It was observed that the weights of the biomass increases with decreasing Cr level in treated effluent with fungi indicating bioaccumulation of the Cr in the cell. In conclusion this study has established that discharge of untreated tannery effluent has negative impact on the environment and it has also established the role and efficiencies of indigenous bacterial and fungal species in the adsorption, accumulation or removal of Cr in the treated effluent. It is recommended that effluent should be properly treated to meet the discharge guideline of 0.5mg/L Cr before discharge and further studies to establish other environmental, health, economic impacts are recommended.
Description
A DISSERTATION SUBMITTED TO THE SCHOOL OF POSTGRADUATE STUDIES, AHMADU BELLO UNIVERSITY, ZARIA
IN PARTIAL FULFILMENT OF THE REQUIREMENT FOR THE AWARD OF DOCTOR OF PHILOSOPHY OF SCIENCE IN MICROBIOLOGY
DEPARTMENT OF MICROBIOLOGY,
FACULTY OF SCIENCE
AHMADU BELLO UNIVERSITY, ZARIA,
NIGERIA
APRIL 2014
Keywords
EFFLUENTS,, TANNERY,, ENVIRONMENTAL,, BIOREMEDIATION,, POTENTIALS,, MICROBIAL,, ISOLATES