A large scale activated sludge system has experienced an illicit industrial discharge of unknown origin. Wastewater analysis showed Petrol derivatives of variable carbon lengths [c3-c20]. Despite full aeration process, DO electrodes are intact, but show zero DO content? Do petrol derivatives impact the oxygenation efficacy? Any experience you can share? How to put the system into operation?
If this industrial discharge strongly increased the organic loading rate of your activated sludge system, oxygen demand could be higher than oxygen supply. In this case, despite full aeration, you will get a DO concentration of zero. Do you know how much the OLR increased compared to normal conditions?
Amazingly COD [S] of the incident [1750 mg/L] was less than that during the normal [1950 mg/L] flow rate; the OLR might have an impact BUT, we looked for toxicants identification, which might have impaired the oxygen transfer rate; mainly chemical toxic substance in the mineral oil [diesel, kerosene, benzene etc..]; odorous phenolic compounds was detected but not measured; heavy metals content was within the limits of municipal discharge into sewer networks.
Rashed, toxic waste typically inhibits the wastewater microorganisms. Under such conditions, microorganisms can oxidize none (complete inhibition) or very little organic material. As a result, much less oxygen is used. Therefore, I would expect higher DO reading under these conditions. I think Nicolas is right in his diagnosis.
That exactly what not happened, biomass is there [anoxic/anaerobic] for a period of more than three weeks, BUT no increased DO [S[, if biomass is dead, then what Ufuk and Nicolas said is correct, however was NOT the case. Anyhow, using ionic chromatography we separated a thin layer of unknown composition [both hydro- & organophoBIC in nature] , that should be behind forming the interface between the gas-liquid phases and hindered DO dissolution into water. We exchanged the whole content and started the system newly. Now the system is running perfect.
That's a great news Rashed. There is possibility that the idendified compounds fouled the DO probe.
NO dear Ufuk, as I mentioned above, I checked the DO electrode and calibrated, it was functional!! Also, I checked the DO using a portable DO meter, zero DO [s]??!
Dear Colleague,
Unless you don't prevent the introduction of petrol derivatives, it is difficult to say that you can do successful treatment. You should prevent the entrance of these pollutants to treatment system. I wonder, entrance of these kind of pollutants are going on continuously or not? If it is not continuously may be you can put a stabilization pond that including ozonation process for example. If COD of influent wastewater is higher than a typhical domestic wastewater may be you can modify the system to anaerobic reactor.
Hi Olcayto,
It is an incident of illicit industrial discharge, hopefully once and the municipal engineer was informed to take ALL possible measure NOT to repeat that. It is NOT a continuous industrial flow. Installing an anaerobic pond is NOT possible as of space and costs. It is an advanced treatment process [MBR] and has coped with the incident through operational modifications over two weeks. All sludge was dewatered [removed] and a new start-up was initiated. Another type of technology will NOT be reliable and the entire process will fail. Here, despite a new start-up, no by-pass of raw WW, and stable recycled water quality, we have had three 10`s [TSS/BOD/Total-N (mg/L)]. MBR technology is the perfect choice opted by the municipality to protect public health and receiving water bodies, a nearby freshwater spring.
- Badges
- Science topic
- Similar topics
- Engineering
- Modeling