Sludge Bag Drainage ("Sackdrain")

Sludge drainage with filter sacks and bags –
a real alternative to sludge drying beds and mechanical processes


The treatment of wastewater is a considerable cost for municipal, commercial and industrial sectors alike. The huge potential for economizing in this area, however, is very often overlooked. Non-optimal treatment of wastewater can lead to high additional costs, which could, in fact, be avoided. 

Very often technology which was originally developed for handling much larger output is adapted for the disposal of smaller amounts of waste.  As a result, this type of treatment needs excessive technological input making it relatively expensive and complicated to operate. Simple treatment processes would fulfill the demands in many areas of use. This also applies to drainage technology used to deal with the unavoidable sludge resulting from wastewater purification.

The diverse possibilities of implementing filter bags, independent of the type of wastewater treatment, are very often ignored. This could be due to the lack of specialist literature about this simple and cost effective process. 

The effectiveness of filter bags is very often under-estimated when it comes to attainable output performance and drying results. As investment and operational costs are so low and handling so simple, there really should be a new focus on this process, especially in the treatment of smaller amounts of sludge waste.

The cost-effective method of sludge disposal can be implemented wherever there are small amounts of sludge and a high level of dry mass content, such as in sewage treatment plants between 5 - 1 000 PE.  

Mode of Operation:

Surplus sludge is extracted from the sludge storage tank using a self-priming pump. At the same time, controlled amounts of flocculation agent are added via a dosing pump to ensure optimal drainage. The mixture is pumped to the actual bag drainage treatment. In the basic module, the filter bags are made of geo-textile.

Due to the shut-off mechanism in the distribution pipeline, the bags can be filled in a series or simultaneously.

It is not possible to overfill the bags as they are fitted with a pressure control valve with a feedback system.

The flocculated surplus sludge remains in the bags and is statically drained. The return flow from the sludge treatment is collected in the tray positioned under the attached grid and channeled back to the wastewater treatment plant.

After a few hours of draining, the bags can be removed and stored in a shelving system. The special features of the bag material produce more moisture through evaporation.  In addition, after a sufficiently long period of storage, solid content is formed which is of a similar quality to that obtained through mechanical sludge drainage.

After some time, the bags of dried sludge can be cheaply disposed of or used, for example, as fertilizer.

A volume and weight reduction of over 95% is possible at anytime using this method.  

Advantages of the sludge bag drainage method