Drying Technology
XXI
Q: The secondary sedimentation tank is circumferentially-feeding and circumferentially-discharging. Within 1m of the outflow weir, there are fine floating particles flowing upward from the bottom of the tank, and the appearance is very bad. Our effluent has not yet reached the standard. COD is about 89mg/l, BOD is about 28mg/l, and SS is about 23mg/l. At present, our bacterial culture work is progressing relatively smoothly. SVI(30) is about 10%. Microscopic examination can see a small amount of rotifers. It has something to do with the rain in the past two days and the large water intake. However, the BOD/COD of our water intake is too low, which slows down the speed of culture work. No mud has been discharged yet. In response to our current situation, I have a few questions:
1. Can we continuously inject water? Is our sludge resistant to general shock loads?
2. The DO of the oxidation ditch is about 8. Is it necessary to open an aerator to push the flow? Or turned on the aerator occasionally? There is an inflow push in front of the oxidation ditch, and a returned sludge push in the tail.
3. When is the estimated time to open the remaining sludge pump? How to control the reflux ratio?
Answer:
1. With a settlement ratio of 10%, f/m should not be greater than 0.25; continuous water inflow is no problem.
2. Check whether the dissolved oxygen of the oxidation ditch mixture flowing into the secondary sedimentation tank meets the requirements. It is enough to have 1.5 dissolved oxygen. It is best to investigate the dissolved oxygen data of the entire oxidation ditch. Then decide the aeration method.
3. If the dissolved oxygen of the oxidation ditch mixture flowing into the secondary sedimentation tank is greater than 3.0, I think that one is energy waste, and the other is that the effluent contains small unsettled activated sludge particles.
4. Intermittent short-time mud drainage is necessary. Otherwise, a settlement ratio of 10% will result in a great discount.
5. The control of the reflux ratio can be adjusted according to the amount of water inflow. It is the same as the traditional sludge method, such as non-removal of nitrogen and phosphorus, 50 to 100%.
6. The production and quantity of rotifers has nothing to do with rain and large water intake. It is related to low load and long sludge age. It also indicates that continuous water intake can be used to increase the load. Of course, proper mud drainage is also required.
XXII
Q:
I want to inoculate UASB! Since I am debugging in a small town, the books are not brought. It is not clear how to control the A section of the AB method. May I ask:
1. Is it continuous backflow from the primary sedimentation tank to section A at the same flow rate?
2. How much should the SV30 be controlled? Is it 5%-10%?
3. Is the primary sedimentation tank waste sludge?
Answer:
My understanding is that the AB method is a two-stage biochemical treatment. It is more advantageous to treat the more difficult-to-degrade organic matter by the AB method because the residence time can be guaranteed.
XXIII
Q: Recently, we emptied the sedimentation tank. I don't know why there was a lot of floating black mud about a day after the water entered. It has lasted for more than a week and still exists. Why does this happen? Is there any way to remedy it or prevent it?
Answer:
1. I don't know whether your sedimentation tank is a sedimentation tank for wastewater treatment or a sedimentation tank for tap water. If it is a sedimentation tank for wastewater treatment, I think you should check whether there is any change in the working conditions of the sedimentation tank before and after cleaning! Such as the amount of influent, dissolved oxygen content of influent, residence time of influent, etc.!
2. As aerobic biological treatment, the sludge in the secondary sedimentation tank turns black and floats. The dissolved oxygen content in the tank should be considered first to avoid hypoxia or anaerobic.
3. Check whether the returned sludge in the sedimentation tank is smooth, whether the return flow is too small, and whether the mud scraping equipment has hidden faults.
4. If the sludge is floating in the primary sedimentation tank, consider whether the concentration of organic particles in the wastewater has increased, whether the sludge discharge is in place, whether the residence time is too long, whether the mud scraping equipment has hidden faults, etc.
XXIV
Q: I would like to ask, our factory processes oil effluent, and now the water quality in the adjustment tank is good, but the aeration tank has poor processing capacity and a lot of oil on the water surface. Is this the cause of the aging of the sludge?
Answer:
Oil is inherently not easily biodegradable, and it has nothing to do with sludge aging.
XXV
Q:
Our company is now taking over the treatment of ammonia distilling wastewater from a coking plant. The activated sludge method was also used in this plant, but due to the extremely high concentration of ammonia and phenol, all bacterial species died.
The water quality is as follows:
COD=8000-11000; Volatile phenol=1700-2300; Volatile ammonia=300; Thiocyanide=635
The pretreatment process we use is:
Distilled ammonia wastewater (alkali addition) → oil separation regulating tank (deoiling) → sealed blow-off tank → dual air flotation → intermediate pool → sand filter
The effect is still not good, is there any better way? What improvements are needed in the pretreatment process?
Answer:
1. For this type of wastewater, the increase in treatment costs is inevitable.
2. To ensure that the effluent reaches the standard, I think that adding A/B treatment in the post-filtration stage may get good results.
3. By increasing the biochemical system, and requiring the design and installation unit to provide design schemes and reasons, and rationally select the biochemical process, there should be no problem.
