Salinization of surface waters poses an increasing threat to low-lying delta regions due to climate change-induced sea level rise and reduced river baseflows, which facilitate saltwater intrusion. In the Netherlands, saline groundwater seepage and the use of brackish flushing water contribute to elevated salinity levels in urban water system, threatening freshwater ecosystems and compliance with the Water Framework Directive (WFD). This thesis investigates how water quality modeling can support the assessment and mitigation of salinization in urban polders in Rotterdam.

The Pernis polder in Rotterdam was selected as the study area. Surrounded by flood barriers, the Pernis surface water system functions as a closed system, where freshwater enters through an inlet structure and is discharged from the polder by pumping. An integrated catchment model was developed in InfoWorks ICM to simulate chloride concentrations throughout the surface water system by combining hydrological, hydraulic, and water quality processes.

Two mitigation strategies were evaluated and compared with the current water system configuration and flushing practice. The first strategy involved real-time control (RTC) of the inlet structure, restricting flushing to periods with low chloride concentrations in the source water. The second strategy consisted of stormwater separation, providing stormwater runoff as a dilution source. Simulation results showed that RTC reduced chloride concentrations below ecologically relevant thresholds for several weeks during the 75-day simulations. Mean chloride concentrations at the downstream pumping station decreased by 423–501 mg/L, while peak concentrations were reduced by up to 1,900 mg/L. These findings indicate that RTC is a mitigation measure of ecological and regulatory relevance. In contrast, stormwater separation produced negligible average chloride reductions and lowered concentrations below ecological thresholds only briefly following high-intensity rainfall events. As a standalone measure, this strategy was therefore found to be ineffective.

Furthermore, RTC was further assessed under a synthetic future worst-case climate scenario (i.e. KNMI’24 Hd scenario for the year 2085), incorporating increased saline groundwater seepage and sea level rise impacts on the Nieuwe Maas. Although RTC continued to substantially reduce chloride concentrations, levels remained above ecologically relevant thresholds throughout the simulation period, indicating that RTC alone is unlikely to prevent future salinization.

Overall, this study concludes that integrated water quality and hydraulic modelling is a valuable decision-support tool for assessing salinization and developing effective future water quality and water quantity mitigation strategies in Rotterdam’s urban water system. ... Read more

This research explores the feasibility of implementing ceramic microfiltration (CMF) treatment in Maputo, Mozambique, to reclaim wastewater for industrial reuse, addressing the city's pressing water scarcity challenges. As rapid urbanization increases Maputo's reliance on potable water for industrial and agricultural needs, this study evaluates reclaimed wastewater as a sustainable alternative to alleviate demand on the city's limited freshwater resources. Using a CMF pilot plant, the project tested wastewater from the recently upgraded Infulene Wastewater Treatment Plant (WWTP) to assess whether CMF treatment could achieve quality standards suitable for applications such as cooling, concrete production, car washes, agricultural irrigation, and municipal park irrigation. Furthermore, the opportunity of scalability was tested through a water balance, while relevant stakeholders were interviewed and costs estimated to complete the feasibility assessment.

Laboratory results indicated that CMF treatment effectively reduces turbidity, chemical oxygen demand (COD), and biological pollutants like E. coli and coliforms. However, dissolved particles and heavy metals were not removed, limiting its efficacy for high-specification uses. While the treated effluent met quality standards for lower-specification applications, such as local car washes and park irrigation, it did not reach the stricter requirements needed for cooling water or concrete production. This underscores a need for process optimization, particularly through coagulation, to expand CMF's application range.

To assess sustainable water availability, a water balance analysis of the Infulene WWTP considered seasonal flows and local agricultural demands. The findings suggest that although the current water supply is insufficient during dry months, full capacity utilization and improved sewer network connections in the future could support CMF-based water reuse consistently across seasons, with potential scalability for additional users.

Economic analysis compared CMF's capital and operational costs with revenue from reclaimed water sales, showing that while considerable initial investment is required, direct piping could potentially make CMF-treated water competitively priced against potable supplies under the condition of reaching maximum treatment capacity at a scaled up CMF plant. High costs associated with truck-based delivery, however, present a barrier to adoption for potential users. Stakeholder interest was strong across industrial users and developers, though contingent on achieving cost parity with the existing water network.

This study concludes that, while integrating CMF technology into Maputo's water management strategy offers promise, challenges remain in achieving quality standards for certain industrial applications and in lowering costs. Addressing these technical and economic barriers could open avenues for CMF's broader adoption, especially with future assessments that include alternative suppliers and configurations. ... Read more