Sometimes, the flow in a system is predictable and acts exactly how we want and need it to. However, other times it can be irrational and not behave as it should. Because of this there are methods we can introduce to stop units in systems from being overloaded by a sudden influx of solids.
If a tanker is pumping its contents into a system, having just collected from a location, you can be confident that the solids are still in suspension. Therefore, they will be somewhat consistent throughout the liquid, thus meaning it will not overload the system, as long as it is pumped at a suitable speed.
If the same tanker has collected waste from another location, and once the contents have been retrieved the tanker is then left for 24 hours, the solids will start to separate and fall to the bottom of the tanker. After 24 hours has passed and the contents are pumped out, there will be a high solids loading on the system, potentially overloading it.
How Can This Be Solved?
One idea can be to introduce a holding/reception tank into the system. This can be specified to the flow rates required or dwell times needed. Doing this will ensure that equipment will not be overloaded straight away. You can use the tank as a storage facility, so when the system is ready, the medium can be pumped out of the tank.
However, this will not solve the problem directly. The use of a holding tank may store the medium, but just like the tanker being left for 24 hours, the holding tank will act exactly the same. If it is not pumped out quick enough, then the heavy solids will settle at the bottom.
To overcome this, much like inside a digester itself, the holding tank would need to be mixed or agitated in order to keep the solids in suspension. This could be through the form of mechanical means such as a propellor mixer. Other methods can be ones like recirculation pumps that are strategically placed adjacent to the tank to ensure the contents are constantly being mixed.
Another aspect to consider is where your pump is located in comparison to the tank. If your suction line is at the bottom of the tank, then you are naturally going to be pumping from the bottom of the tank first.
