<p>Water treatment on tunnel construction sites is an essential yet often underestimated aspect of the construction process. In many projects, the handling of process and wastewater poses technical, economic, and environmental challenges. Effective treatment systems are crucial not only for complying with legal discharge limits but also for ensuring operational safety and cost efficiency on site.</p><p>This contribution examines the relevance of water treatment in tunneling and explores whether its importance is underestimated or overrated in practice. The focus lies on a&#xa0;combination of chemical and mechanical processes to ensure an efficient and sustainable purification of wastewater. Suspended solids, heavy metals, and dissolved contaminants are specifically removed so that the water can either be reused or safely discharged into the environment. Various reuse options are considered, such as dust suppression, slurry preparation, or machine cooling, which can significantly reduce water consumption on construction sites.</p><p>A&#xa0;key factor is compliance with regulatory limits, which can vary greatly depending on site, region, and environmental requirements. In many cases, specific thresholds for pH, turbidity, heavy metals, and chemical oxygen demand (COD) must be met, regardless of changing geological or hydrological conditions.</p><p>Particular attention is paid to the economic and ecological aspects of water treatment. While some projects consider the effort unnecessarily high, it becomes clear that early and well-planned integration of treatment systems can reduce both long-term costs and environmental risks. Incorporating water treatment solutions into the construction process enables stable compliance with regulations, minimizes costly downtime, and optimizes resource use.</p><p>Furthermore, the contribution highlights how modern sensor technology and automation can further increase treatment efficiency. Intelligent control systems ensure optimal chemical dosing, minimizing both chemical consumption and operating costs.</p><p>A&#xa0;current project in Germany is used to demonstrate how innovative water treatment technologies can provide efficient and sustainable solutions for handling wastewater.</p><p>Is it therefore an underestimated necessity or an overrated challenge? This question will be addressed.</p>