Floating sludge appears on the surface of the sedimentation tank, which often increases maintenance troubles for wastewater treatment operators And the hidden worries of letting go of water~
We provide three possible reasons to help operators determine and improve the problem of sludge floating! !
In past experience, it is often found that sludge is observed floating in the water or on the water surface in wastewater pools. The thickness and area vary depending on the wastewater characteristics of each wastewater treatment plant. one. This problem may have existed for a long time and cannot be solved, and it often troubles the wastewater treatment and maintenance personnel of the existing plant. I once heard a person in charge of wastewater from an electroplating processing plant mention that the problem of floating sludge in the wastewater plant has lasted for more than five years. A layer of about ten centimeters of floating sludge often accumulates on the surface of the elevated sedimentation tank, causing irregularities in the outflow water. It is stable, so it is still necessary to install a filter screen for final filtration before discharging. Whenever the floating sludge in the sedimentation tank is cleaned, the sludge will gradually accumulate into layers in about a week, and the cleaning action can only be regarded as a regular maintenance item.
▲Through the Jar Test/bottle cup experiment, the optimal amount of coagulation and gelling agent can be obtained, but the actual sludge settlement situation cannot be known
Based on actual visit experience, we found that there are three main reasons for the floating of suspended solids or sludge/floating plastic feathers in the sedimentation tank. The sludge formed is too light, the sludge contains grease, and there are air bubbles attached when the sludge is formed. The following is a further explanation of these three possible reasons for the reference and self-examination of each wastewater plant.
Reason 1: Too light sludge/plastic feathers
It is caused by the fine suspended matter produced at the process end, such as the grinding abrasive grains present in wafer grinding/cutting or the fine particles produced by cutting. Because the amount of coagulant added is too small, or the composite feathers formed are still too light, the sedimentation tank is ineffective and there is still suspended white sludge on the surface.
▲Fine suspended solids are often disturbed by the water body and suspended on the water surface
Reason 2: Oily sludge/plastic feathers
This situation often occurs in wastewater treatment tanks in metal processing plants. Since metal processing rooms often need to prevent metal from rusting, anti-rust oil is used on the surface of the workpiece before transportation to prevent it from rusting. When entering the next process, the anti-rust oil on the surface must be removed. If there is grease remaining on the surface, it will affect the quality of the subsequent process. After the grease is removed and rinsed, a stream of wastewater containing grease will be produced. . When this wastewater is discharged into the wastewater pool, a layer of grease will form on the surface of the pool. Although the addition of coagulant (PAC) and polymer flocculant (PAM) will form a complete sludge/gel plume, it will be suspended on the water surface because it contains oil, causing the sludge to float.
▲The oil layer floating on the surface will cause the sludge to contain grease and suspend after coagulation/flocculation
Reason 3: Bubbles adhere to sludge/glue feathers
This situation may occur in various manufacturing processes. The main reason is that the wastewater may contain trace amounts of surfactants, which may be caused by a small amount of cleaning agents or additives in the manufacturing process. When the wastewater treatment system is drained by water pumps, or the difference between high and low liquid levels causes disturbances and the formation of tiny bubbles. If these tiny bubbles occur at the same time as the formation of rubber plumes/sludge, it is very likely that the two will adhere and cause the sludge to float.
▲After magnification, it can be clearly observed that tiny bubbles adhere to the sludge, causing the sludge to float
The cause of sludge floating is not easy to observe and discover at first glance. It is necessary to understand the flow of the wastewater system and gradually eliminate possible factors by following the direction of the water flow. The real reason for the rise will be discovered. The above three causes of sludge floating are the main reasons summarized by Kelly Chemical personnel when they visit the site when serving customers. Depending on the characteristics of wastewater, wastewater treatment process and on-site configuration will determine whether the supernatant liquid in the back-end sedimentation tank is clear or fuzzy. The sludge is suspended, so in each case, the cause of floating may be found in different places, and there are corresponding solutions. Therefore, we sincerely welcome to contact the local Kelly Chemical personnel for more detailed consultation on related issues.
