Improvement potential of residuals from WML drinking water production

The drinking water production process at Limburg Water Distribution Company (WML) results in a variety of residuals: liquid aquafer, lime pellets, back-wash water, (iron) lime sludge and filter medium. Reststoffenunie disposes of all of WML’s residuals, with the exception of processed back-wash water. The preference for waste management is to prevent the production of residuals or reduce their volume, but this is not always possible in practice. The valorisation (increasing the value) of residuals is then a good option: it can have a significant impact on the disposal costs and contribute to sustainability, but it can never of course be at the expense of the quality of the primary product: drinking water.

The objective of this project was, on the basis of 2013 data from WML and Reststoffenunie, to analyse the possibilities of lowering residuals costs and enhancing the sustainability of the processes.

Structured inventory of data

We structured the 2013 data from WML and Reststoffenunie for clusters of production locations. The clusters were defined according to the type of water treatment and the expected residuals. We then conducted comparisons at different levels (per material, per cluster, by residual volume, cost and earnings). We used the quality features of residuals to identify potential (new) markets, considering the specific quality requirements of clients and legal and regulatory prescriptions. We also examined in general terms the potential use of a more advanced back-wash water treatment process, which results in aquafer of higher value.

Better insight into residuals process

The research led to a better understanding of the residuals process, besides specific improvement possibilities, per residual and per location, and a series of general recommendations. With these results, WML can focus on those residuals and processes that involve high added value and also offer improvement potential. At the same time, appropriate attention should continue to be paid to those residuals whose processing and sale are on a good course. In addition, more effort could be made to draw the attention of WML staff to the importance and potential of processing residuals well.