Microbiological assessment of treated wastewater and detection of antibiotic and chlorine resistant Escherichia coli from wastewater treatment plants in Oman / Intisar Salim Al-Gharibi
Oman depends on recycling its treated wastewater as a solution to overcome its limited water supplies and public health safety is therefore an important consideration. This study was carried out to assess the microbiological quality of treated wastewater samples from two wastewater treatment plan...
| Main Author: | |
|---|---|
| Format: | Thesis |
| Language: | English |
| Published: |
2011
|
| Subjects: | |
| Online Access: | http://ir.uitm.edu.my/id/eprint/4265/ http://ir.uitm.edu.my/id/eprint/4265/1/TM_INTISAR%20SALIM%20AL-GHARIBI%20AS%2011_5%201.pdf |
| Summary: | Oman depends on recycling its treated wastewater as a solution to overcome its
limited water supplies and public health safety is therefore an important
consideration. This study was carried out to assess the microbiological quality of
treated wastewater samples from two wastewater treatment plants (WWTPs) in
Oman, the Royal Hospital WWTP and Barka WWTP. This analysis was conducted
on secondary and tertiary as well as de-chlorinated tertiary treated wastewater which
were sampled during the summer and winter months from August 2007 to January
2008. The aims of the study were also to detect antibiotic and chlorine resistance in
Escherichia coli using disk diffusion method. Sodium hypochlorite was used as a
source of chlorine in the latter. Microbiological analysis showed that highest
heterotrophic counts obtained from secondary, tertiary and de-chlorinated treated
wastewater from both plants were from samples collected in August 2007, and the
lowest were from samples collected in January 2008.
This indicated that the heterotrophs were affected by the variation in seasonal
temperatures. Analysis on the heterophic counts at three different incubation
temperatures, 22oC, 37oC and 42oC indicated that the indigenous aquatic
heterotrophs were more affected by the seasonal temperature variations compared to
those of human and animal origin and thermotolerant heterotrophs. Total and faecal
coliform counts in secondary, tertiary and dechlorinated tertiary treated wastewater
samples from Barka WWTP were higher in the summer months and lower in the
winter months but in the Royal Hospital WWTP this trend was not obvious in the
tertiary de-chlorinated samples. The faecal coliform counts in the tertiary treated
wastewater samples of both plants however, fell within the acceptable limits of
Omani standards for use in watering public parks and landscapes. The enterocci
counts in both plants were also higher in the summer months than in the winter
months.
Fifty seven confirmed E. coli isolates from both plants were tested for susceptibility
to sixteen antibiotics namely Amikacin, Ampicillin, Chloramphenicol, Ciproflaxacin,
Gentamyci, Cephotaxin, Kanamycin, Cephalothin, Minocylin, Neomycin,
Nalidixicacid,S ulphamethoxazole, Streptomycin, Tetracycline, Tobramycin and
Trimethoprim. All isolates from the Royal Hospital plant were resistant to at least
two antibiotics, whereas those from the Barka plant were resistant to at least one.
Tetracycline resistance was exhibited in 86.6% and 62.9% of the isolates from the
Royal Hospital and Barka plants respectively. Multiple resistances to cephalothin and
tetracycline were exhibited by 90% and 37% of the isolates from the Royal hospital
and Barka plants respectively. All isolates were resistant to 0.5 mg/l sodium
hypochlorite and the minimal inhibition concentration of 2.5 mg/l sodium
hypochlorite was only exhibited in 24% of the isolates. |
|---|