Polyferric sulfate is a kind of water purifying agent widely used in ferric salt flocculant. Some users have reported that the water at the outlet of sedimentation tank turns yellow after adding PFS. If you want to know the reason, follow Zhengyuan to understand it
The first reason is whether the waste water is yellow or not.
Polymerized ferric sulfate, ferrous chloride and other iron coagulants contain a large number of 3-valent iron ions or 2-valent iron ions. If excessive iron ions are added into the wastewater, a large number of iron ions will appear yellow in the wastewater. If there is sulfide in the wastewater, iron ions will react with sulfide, which is also the reason for the yellow of waste water. Therefore, the dosage of ferric ions should be strictly controlled.
2. The sedimentation effect of sedimentation tank is poor
If too little PFS is added, the organic matter and metal ions in the wastewater are not oxidized, which may cause the water body to turn yellow. Or if the aeration rate is too large, the original floc will disintegrate again and make the water turbid. If ferric salt is used as coagulant or the suspended solids in raw water are yellow, the effluent may turn yellow or the flocculation effect of activated sludge is not good, which will disintegrate in aeration. It can be treated by adjusting aeration rate or increasing PFS dosage.
3. The retention time of secondary sedimentation tank is short or sludge discharge is not timely
Sludge can not be precipitated in the tank and suspended in the wastewater, resulting in yellow effluent and substandard SS. It can be treated by extending the residence time. The sludge entering the secondary sedimentation tank accumulates continuously and produces nitrogen and other gases to come out of the water surface. During this period, these tiny bubbles will wrap up a small part of the sludge and float up, thus increasing the turbidity of the water body. To solve this problem, it is necessary to discharge the sludge in time to prevent the sludge from breaking and dissolving in the water.
The above three cases will appear yellow water, sometimes yellow is not the reason for adding PFS, of course, in the three cases, too much PFS is a common situation.
According to the above three points, we can find the reason and solve the problem!