Water

Water is an extremely precious resource – not only as drinking water, but also as a raw material, solvent and coolant in many technical and chemical processes. At WACKER, we use water sparingly and protect natural water resources. We always purify our wastewater as effectively as possible and recycle the water by means of cycles in our production. We make sure that this multiple use does not increase energy consumption or otherwise negatively impact the environment.

We use the Global Water Tool^© (GWT) developed by the World Business Council for Sustainable Development (WBCSD) to analyze the annual relative water stress index of the countries in which our main global production sites are located. This assessment has been conducted since 2012, based on analyses using the water stress index developed by the Water Systems Analysis Group of the University of New Hampshire, USA. This index provides information on the relationship between water consumption and the availability of renewable fresh water. The outcome of the analysis is that our most important production sites are located in regions with a low relative water stress index. These regions account for more than 97 percent of our annual water use and over 90 percent of our production volume. Production sites in countries for which no GWT-based water stress index information is available account for less than 0.5 percent of our water use.

Together with seven other companies from ChemDelta Bavaria, we established the Naturnahe Alz (Natural Alz) association (German-language version only), through which we support the state of Bavaria in renaturalizing the Alz river and enhancing its ecosystem long-term.

In 2016, we cleaned up and repaired the roughly 17-kilometer Alz canal at the Burghausen site. Its water is used to generate power as well as supply cooling and process water for the Burghausen site. To ensure that the waterway ecology would not be compromised during the clean-up phase, we used a monitoring program to control the alternative intake of cooling and process water and the altered disposal of cooling/process water and wastewater. We used the Salzach river as an alternative source of cooling and process water, as it has a much lower temperature than that of the Alz canal. As a result, much less water was required, though the power consumption for pumping was higher. That is why, post clean-up phase, we are again using water from the Alz canal, which consumes less power.

COD (chemical oxygen demand) effluent burdens rose in 2016 as a result of the new polysilicon production plant in Charleston (USA).

The 2016 increase in AOX (adsorbable organic halogen compounds) was caused by a discharge from a company based at the Burghausen site accidentally entering WACKER’s captive sewer system; the discharged substance did not adversely impact the environment.

In 2015, we obtained a permit as required under German water law in order to withdraw more groundwater at the Burghausen site in the future. This allows us to ensure the quality of our ultrapure water supply and to bridge periods of poor quality surface water. An extensive monitoring program accompanies the withdrawal of groundwater. This includes groundwater level measurements, discharge measurements at three streams in the Haiming municipality and a functional check of the habitats in the riparian woodland, including nature-conservation inventories. This is how we ensure that the groundwater withdrawal does not negatively impact registered protected areas.

At the Burghausen site, WACKER SILICONES has been reducing the organic burden within the effluent feed to the biological wastewater treatment plant by means of Fentox^® split-stream treatment since 2015. Over the last seven years, we have continually reduced the volume of harmful substances emitted into the Salzach river. We switched the biological wastewater treatment plant’s first bio-stage from double-tank to single-tank mode and started operation of an additional intermediate wastewater storage tank. We use it to collect peak pollutant loads so that they can be fed into the biological wastewater treatment system in a controlled manner during phases of low influent from production. The consistent feed-in supply leads to more stable operation of the biological wastewater treatment plant. Emissions of organic pollutants to the Salzach river have decreased by 42 percent since 2010.

In Burghausen, we established new protective measures for the stormwater sewer system in the period under review: to avoid substance discharge into the stormwater sewer, special mats are now available for gullies and manhole covers. The aim is to prevent substances such as petrol, hydraulic fluid or products from plants from running into the stormwater sewer via the road drainage system in the event of an accident involving substance escapes.

The process water used at Nünchritz comes from on-site wells (2016: 4,059,847m³, 2015: 4,291,069 m³). Drinking water accounts for less than 1 percent of our total water use at this site.

We built a new culvert at the Nünchritz site in 2015, because the two existing water supply lines are already 50 and 80 years old. The process water needed for production is extracted from wells on the left side of the Elbe river and conveyed underneath the Elbe and into the site. The new culvert did not alter water use; the well water flow rate averages at around 500 m³ per hour. The water is primarily used for cooling plants; wastewater passes through the treatment plant and back to the Elbe.

“Save Wastewater and Make a Profit” was the title of a special Employee Suggestion Program initiative that took place at the Nünchritz site from December 2014 to September 2015. The purpose of the initiative was to encourage employees to develop ideas for conserving and recycling water in production, thereby raising their general awareness for reducing wastewater. In the course of the initiative, wastewater in the central wastewater treatment plant at Nünchritz went down by some 5 percent. Since 2010, specific water use at Nünchritz has halved, even though wastewater volumes rose overall due to polysilicon production expansion.

Despite higher purity requirements, we have conserved water in production at Siltronic, e.g. by using circulation water in processes with lower purity requirements, letting the purification bath stand for longer, and reusing concentrate from reverse osmosis for mechanical processes (such as air scrubbers, lapping and wire-sawing). Siltronic has saved around 39 percent water at its Portland, USA, site since 2013, for example. We monitor the use of ultrapure water in wafer production; Siltronic achieves a water-recycling rate of up to 45 percent.

The town of Freiberg obtains its water from the Lichtenberg Dam. The Siltronic site there uses the surface water from the dam for cooling crystal pulling facilities. It is furthermore purified into hyperpure water for wafer production. Surface water from the man-made Kohlbach ditch is now only carried to the site for the emergency cooling of the crystal pulling facilities. In connection with the construction of the new pulling hall, the Freiberg site gained a rain retention basin with an emergency function. In an emergency, polluted wastewater can be separated into a basin made of reinforced concrete. The new plant construction makes the site’s drainage system state of the art and contributes to further reducing the risk of pollution of the Münzbach and Mulde rivers in the case of an accident.