The closed loop system is projected to save 10,000 m3 of water per year, over the next two years, and is also a live working showcase of how wastewater can be treated effectively at source. Project manager Klaus Andersen explains that the painting system is a CED (Cathode Electro Deposition) system, which sees components painted evenly as they are dipped.
THE NEW RECYCLING SYSTEM
When it comes to recycling wastewater, Grundfos begins by separating the rinse water from the other process wastewater, and then established storage capacity so it can run a stable flow process. “The pollution comes from the pre-treatment of the products and rinsing after the painting steps. [It] is basically metals, acids and salts,” explains Andersen. “There is hardly any oil and grease in the rinse water. The amount of rinse water is 10,000 m3 from both the cast iron process and the aluminium rinse process.”
The water is cleaned through microfiltration, followed by the use of reverse osmosis (RO). Grundfos then loops back the same water to the process again after it has been treated. “We know there are losses in the system. We are losing around 20% of the water in the RO process,” says Andersen. “Presently this is being replaced by tap water, but in the future other wastewater stream will be used.”
The clean water is held in a tank and, to avoid bacterial regrowth, treated with UV disinfection. “The demand for the rinse water is a conductivity under 15 micro Siemens and pH of around 4-5, and a bacteria level under 1,000 bacteria/ml – so here we are using RO water made in a traditional system,” he adds. “We are adding a scale inhibitor chemical to prevent fouling of the membranes and extend the lifetime. Then we have the option of adding chemical to the CIP process when we clean the system. And if the bacteria level increases sufficiently, we will disinfect the system with hydrogen peroxide.”
Principal components of the new system include tanks and pipe racks, as well as digital sensors, micro filtration, smart dosing and Grundfos pumps. To be more precise, it uses digital dosing for adding the correct amount of chemicals to the process and a Grundfos sensor is used for pressure, temperature and flow control. Furthermore, Grundfos BACMON offers the online possibility of detecting bacteria in the water, and gives as an early warning if the bacteria level is increasing.
“The project has increased the process knowledge where we now have online control with a very important parameter in terms of the bacteria level. We are also slowly transforming our handling of the wastewater to be a supplier of water to the production,” adds Andersen.
SAVINGS
Grundfos estimates a yearly water consumption reduction of 5,000 m3 in 2019. In addition, savings during 2019 will aim to produce a reduction in total water consumption of 7% and a reduction in wastewater from production of 16%.
In 2017, the total amount of water used in the whole painting process was 15,424 m3 per year. This total amount of water went to Grundfos’ own wastewater treatment plant – where there is a combination of chemical and mechanical treatments. Clean water is dispersed to the local municipality sewer and sludge sent for reuse in a local company, who use it to fuel its production.
“We are removing the wastewater from our traditional wastewater treatment plant so, here, we will save chemicals for flocculation and coagulation. This will also reduce the amount of sludge from this treatment. We have not quantified this yet,” adds Andersen.
“All the way we have had a very close cooperation with production, an internal Grundfos water treatment specialist and an internal product specialist. We made a choice to build the system internally and do all the commissioning ourselves. The basic reason was that we want to build in all the Grundfos technologies that we could and make a learning platform to help in our own development.”
Note: This article was first published in Engineer-to-Engineer, Operations Engineer magazine, April 2019.