A layer of organic material is formed in drain water silos during use. This leads to the silo having less of a buffer and also is a potential nutrition source for a variety of microorganisms that can settle in the sludge.
Now that the reuse of filtered water is often done through the silo so it can be used as drain water, more sludge is accumulating than in the past. That is why it is important to clean out the drain water silos, says Jim van Ruijven of Wageningen University & Research. The sludge is removed from the silos like a watery mass, after which it has to be disposed of by an authorized processor. “Letting the sludge sink and draining the water on top can cause a decrease in the amount of material that needs to be disposed of, thus cutting the costs.”
Source: Glastuinbouw Waterproof