Original Article | 2009, Vol.31, No.5, pp. 567-579
Treatment efficiency in wastewater treatment plant of Hat Yai Municipality by quantitative removal of microbial indicators
Duangporn Kantachote, Kanthasorn Dangtago and Cherdchan Siriwong
pp. 567 - 579
Abstract
The efficiency of treatment in a wastewater treatment plant of Hat Yai Municipality through stabilization ponds and constructed wetlands was monitored by using the bacterial indicators, total coliforms (TC), fecal coliforms (FC), Escherichia coli and fecal streptococci (FS), and photosynthetic microbes. The sequence of water flow in the wastewater treatment plant is as follows: primary or anaerobic pond (P), facultative pond (F), maturation pond (M), constructed wetlands (W1, W2 and W3), and an effluent storage pond (S for the treated wastewater). The wastewater treatment plant has an approximate area of 3,264,000 m2 (2,040 rai) and its dry weather flow was running at only 40,000 m3 / day. There were 10 sampling times used for all the 7 ponds during July-October, 2006. Statistical analysis using a Two-Factorial Design model, indicated that pond types significantly affected temperature, dissolved oxygen (DO), and pH (p<0.05), whereas the time of sampling during the day had a significant effect (p<0.05) only on the temperature and light intensity available to the ponds. There were also significant different removal efficiencies of the different bacterial indicator groups tested (p<0.05). The overall performance of the wastewater treatment plant effectively removed TC, FC, E. coli, and FS as follows, 99.8%, 99.8%, 75.8% and 98.8%, respectively. The amounts of bacterial indicators, except for E. coli, showed a negative correlation with levels of light intensity and DO, whereas there was no correlation between the pH and the different indicator bacteria. There was a positive middle level correlation between pH and chlorophyll a. There were five different divisions of photosynthetic organisms detected throughout the plant as follows, Cyanophyta, Chlorophyta, Bacillariophyta, Euglenophyta, and Pyrrhophyta. The least diversity was found in the anaerobic pond (P) as there were only 15 genera. Euglena, an indicator of dirty water, was detected only in this pond. The greatest diversity was found in the effluent storage pond (S) with 24 genera and Peridiniopsis normally found in fresh water, was only detected in this pond. Increased diversity can be equaled with increased purification.
