Current and future state of groundwater salinization of the northern Elbe-Weser region

Salinization of the upper aquifer of the northern Elbe-Weser region almost extends to the surface. Chloride content exceeds 250 mg/l and the groundwater is therefore, according to the German Drinking Water Ordinance, not suitable as drinking water. The chloride content in the aquifer originates from early flooding with seawater which occurred during the Holocene sea level rise. Depth and extent of the salinization were mapped by airborne electromagnetic surveys and validated by groundwater analyses. In the transition zone between the marshlands and geest areas, the fresh-saline groundwater interface falls to a depth of > −175 m NHN. Due to the extensive drainage of the marshlands, seepage of fresh groundwater is impeded. Instead, an upconing of the fresh-saline groundwater interface appears due to an upwardly directed hydraulic gradient. Due to climate change, chloride concentrations will increase along the coastlines. Further inland, a decrease of chloride content in near-surface groundwater will occur.

The AquaNES Project: Coupling Riverbank Filtration and Ultrafiltration in Drinking Water Treatment

Natural water treatment techniques combined with engineered solutions were investigated at demonstration sites in Europe within the AquaNES project. Ultrafiltration is well-established in water treatment, but is not feasible for many water utilities due to its high operational costs compared to conventional treatment. These differences in cost are caused by membrane fouling and the associated cleaning required. This study aims to assess the economic and energetic operation factors based on studies of an out/in ultrafiltration treatment plant for river water and bank filtrate. The fouling potential of both raw water sources was investigated as well as the quality of the resulting water. In addition, the results show the potential utility of a combined approach utilizing bank filtration followed by ultrafiltration in drinking water treatment. In a separate consideration of the treatment process, the water quality does not fulfill the requirements of the German drinking water ordinance. A new method for the removal of dissolved manganese from the bank filtrate is presented by inline electrolysis. While this improves water quality, this also has a significant influence on fouling potential and, thus, on operating costs of ultrafiltration. These aspects lead to a fundamental decision for operators to choose between more costly ultrafiltration with enhanced microbiological safety compared to cost-effective but less stringent drinking water treatment via open filtration.