Several methods for sewage discharge and replacement in circulating water systems
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As is well known, when the turbidity or total phosphorus level in the circulating water is high, it is necessary to replace the water in the circulation tank. Common displacement methods include: 1. The method of draining first and then adding water. The main steps are as follows: 1. Open the drain valve, lower the liquid level in the tank to around 70% (adjusting it according to actual conditions to ensure that the circulation pump can generate sufficient pressure), close the drain valve, and open the make-up water valve to fill the tank. 2. Once the tank is filled, close the make-up water valve and open the drain valve; repeat step 1. 3. Repeat these two steps until the turbidity or total phosphorus level of the circulating water meets the required standards. II. Add water while draining, that is, open both the discharge valve and the make-up water valve of the circulating water tank simultaneously until the turbidity or total phosphorus level of the circulating water meets the specified standards. Of these two methods, I believe the second one yields better results than the first; in other words, with the same amount of water added, the percentage decrease in the turbidity of the circulating water is higher when the second method is used. Another point is that with the second method, the rates of wastewater discharge and water addition also affect the effectiveness of the replacement process; with the same amount of water added, completing the replacement in one hour yields better results than doing it over two hours. The above are merely personal opinions; I hope colleagues will share their own views!
The second method is commonly used, as it also facilitates control and water conservation.
I tend to prefer the second option, as it’s easier to control...........
Our control method is to force backwashing of the valveless filter. It saves circulating water while achieving the goal of reducing turbidity and total phosphorus.
The water level in our tank and the make-up water valve are under interlocked control; basically, the waste water discharge method is similar to the second one
The second method is easier to control; we have been using the second method
I think it depends on the specific system; use the first method for small systems and the second for large ones.
Valveless filter beds are the best option, as they continuously filter out the suspended solids in circulating water. As these solids accumulate and the resistance of the filter media reaches a certain level, backwashing takes place automatically to remove the dirt. As long as the valveless filter is suitable, it’s convenient.
The theoretical calculations for continuous wastewater discharge and water replenishment are available in physical chemistry textbooks; calculus is required for these calculations, which I have forgotten. According to this theory, the second approach to achieving the same concentration is the one that saves water.