| Author | Wickramaratne, M. S. |
| Call Number | AIT Thesis no. EV-95-23 |
| Subject(s) | Factory and trade waste--Research
|
| Note | A thesis submitted as partial fulfillment of the requirements for the Degree of Master of Science. |
| Publisher | Asian Institute of Technology |
| Series Statement | Thesis ; no. EV-95-23 |
| Abstract | Irregular influx of toxic substances into the influent of Common Treatment Plants, in Industrial Estates is a common occurrence. The operation of an On-line Toxicity Detection System in the influent line of the treatment plant would help to provide early warning signals to the plant operator, and protect the treatment plant. A Toxicity Detection System which relies on measurement of the changes in respiration rate of activated sludge caused by the presence of toxicants was developed in this study. The design and operation of this system was based on similar systems recorded in literature. Sludge mixed with substrate (synthetic feed or waste water) was passed through a respiration chamber. This was operated in two modes to obtain the change in Dissolved Oxygen (DO) caused by the respiration that occurs in the chamber. DO curves were utilised to calculate the respiration rate per minute. Laboratory studies were carried out varying design and operational parameters to determine the conditions required to obtain stable DO curves, giving the maximum possible rate of respiration. Results indicated that operation of the system at a flow rate of 8 Lpm and using a respiration chamber of 1 L volume enabled the obtaining of stable curves. Under these conditions, the rate of respiration was not affected significantly by changes in organic loading, indicating that the system was being operated at the maximum rate of respiration. Control and maintenance of sludge characteristics was seen to be very important in minimising variations in the respiration rate. Operating the system under these optimal conditions , the sensitivity of the system to selected toxicants was determined. It was seen that the sensitivity of the system .could be increased by providing a contact time of 15 minutes between the sludge and the toxicant. The lowest concentration causing inhibition of respiration for the toxicants tested for, at 15 minutes contact time was seen to be 0.5 , 1.0, 10.0 and 12:5 mg/L in the sludge/feed mixture for Hg, CN, Cd and Cr respectively. Its sensitivity therefore is for a range of toxicant concentrations much higher than that permitted in influent to a Common Treatment Plant. The system was applied for mixed industrial waste water by installing it in the influent line of a Common Treatment Plant at Lad Krabang Industrial Estate. It was seen that the system was not sensitive to the range of toxicants present. Inhibition of respiration was seen with samples of waste water from industries known to be generating toxic waste. The concentrations of the toxicants tested for in these samples, were seen to be lower than the level determined to be inhibitory to respiration in the laboratory. The inhibition could be due to the presence of toxicants not tested for, extreme pH values or synergistic effects. The system developed in this study could therefore be utilised on-line for mixed industrial waste water to provide warning of shock loads that could occur due to accidental discharges or spills. It could also be applied in the effluent line of individual industries to provide warning of toxic conditions. |
| Year | 1995 |
| Corresponding Series Added Entry | Asian Institute of Technology. Thesis ; no. EV-95-23 |
| Department | Other Field of Studies (No Department) |
| Chairperson(s) | Stoll, Uwe |
| Examination Committee(s) | Reutergardh, Lars;Yang, Byung-Soo;Kamei, T. |
| Scholarship Donor(s) | DANIDA & AIT |
| Degree | Thesis (M. Sc.) - Asian Institute of Technology, 1995 |