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Modular Wastewater Treatment Whey, Rinse and Germs: A Modular Wastewater Treatment Tackles the Challenge

Author / Editor: Dominik Stephan* / Dominik Stephan

Not all milk becomes cheese: Whether in the dairy, during parts washing or in the hospital, the challenges for wastewater treatment are immense. It is therefore even more important that a modular system is equipped with the appropriate processes and technologies.

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(Source: Grundfos)

Mozzarella is an Italian export hit. Whether on pizza, with pasta dishes or as a snack — the soft cheese has fans all over the world. But not all mozzarella comes from Bella Italia. Even in Danish Jutland, where you’d rather expect Esrom, Havarti or Danish Blue, the semi-solid white cheese with the mild aroma has its fans. At Rødkærsbro, about 30 kilometres northwest of Arhus, the Danish-Swedish cooperative Arla runs one of the largest mozzarella dairies in Europe.

But not everything that is milk becomes cheese. What remains after the coagulation of the raw cheese known as “curd” is the so-called whey. A watery, yellowish liquid that consists of water, lactose, vitamins, lactic acid and proteins. Whey is not waste, as it can be used to produce animal feed, drinks or as a source of protein. The leftovers — and in an industrial cheese dairy this is a lot — go down the drain.

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This does not mean that excess whey is simply dumped into the receiving water. It must be treated to prevent streams, rivers and lakes from eutrophying. Thus, a small wastewater plant with a capacity of 1,000 m3 per day cleans all of Arla’s liquid wastes according to the strict Danish rules for drinking water. This does not only mean the clarification of aqueous components but also urea, which poses a challenge for many conventional sewage treatment processes.

It's a good thing that a company that knows about water is located nearby: since starting with water pumps in the post-war period, Grundfos has become one of the leading suppliers of fluidic solutions. And the world market leader by no means stops at the pump.

Water is a matter close to the heart of Grundfos CEO Mads Nipper: the former Lego manager has put the United Nations’ SDG6 sustainability goal of making clean water and sanitation accessible to all on the company’s agenda. Accordingly, technologies for biological or physical-chemical purification are part of the Grundfos portfolio. And they come in a very Danish building block design.

Modular Sewage Treatment

Biobooster is the name Grundfos gives to its biological wastewater treatment system, which relies on tube bundles instead of huge sedi­mentation tanks. After the biological treatment in large, well-ventilated tanks of an activation stage, the wastewater is forced through the tubes filled with rotating membranes. The clarified water flows into a central outlet, while even the smallest solids remain on the membrane surface and are sheared off by the rotating movement.

Thus, the cleaning performance is maintained, while remaining sludge can be returned to the activation process. Even bacteria get caught in the ultrafiltration membranes and do not reach the receiving water, explain the company’s specialists.

Membrannes Ensure Small Footprint

What sets Biobooster apart is the membrane design. This setup enables a compact and efficient arrangement in a common frame module. Almost a complete water treatment system can thus be realized in the size of two standard containers. Decentralised, simple and independent, Biobooster enables a modular waste water treatment system. Manufactured and delivered pre-assembled from the factory, the plant can be erected and put into operation within a few days. If additional capacities are required, further tubes or modules can be added.

This way, between 100 and 3,000 m3 of waste water per day can be clarified — simply automated and almost without human intervention. Should the diaphragms become clogged during operation, the control software of the pumps will detect a pressure increase. Due to the redundancy of the modules, individual tubes can be serviced without impairing the performance of the entire system. But this is only one of the functions of the monitoring systems: the scope of delivery also includes 24/7 support through intelligent evaluation of operating data, online visualization or on-site support via data goggles for technicians in the plant.

Exceeding the Standard for Drinking Water

As of today, Arla uses a Biobooster unit to purify 450 m3 of water to drinking water quality or better — with a nitrogen content of 1.5 mg/l and 0.12 mg/l phosphorus, the liquid remains well below the strict limits of 8 mg/l and 0.3 mg/l respectively. In addition, another 300 m3 can be used as service water in processes that do not require the same purity. More than 700,000 l are thus saved and do not pollute the local sewage systems.

Smart, modular and decentralised, Biobooster is not only used in the food industry, but also in municipal plants, in the biogas sector or in manufacturing operations. Between 2018 and 2019, Grundfos supplied 13 Biobooster units to a wide range of customers, including two to Arla — the dairy giant also uses the technology at a site in Sweden. Nevertheless, the compact water treatment system is not an all-rounder: As the name implies, Biobooster only works with an upstream biology. But what happens when it comes to purifying rinse from industrial production?

Of course, we are not talking about dishes at the factory canteen, but about sheet metal and parts, for example in the automotive sector. The dimension of this problem becomes clear when one considers that more than 600 million euros are spent on “parts washing” in Europe alone (e.g. for machines, filters and chemicals).

Heavy Metal and Water? How to Clean Rinse Residues

But clean parts give dirty water: whether metal chips, abrasive paste or aggressive cleaning chemicals, nobody wants to find these residues in their washbasin. This problem is not only faced by car manufacturers: Grundfos itself produces thousands of components, housings and blanks every day. However, the wastewater produced during the washing of these parts caused high costs, a great deal of effort and, not least over time, rejects in the washed parts.

The solution: Dynafilter. These filtration modules also use rotating discs, in this case made of silicon carbide, to remove residues from the wastewater safely and economically. The extremely hard material is resistant to both high temperatures and chemicals. The filter module has a footprint of only 1.6 m2 and operates in automatic mode with backwashing. This way, up to 95 % of the water can be cleaned and recovered.

This pays off: for its own systems, the Danish pump manufacturer states a water saving of 36 % with 45 % less use of chemicals. The energy requirement could also be reduced by 1,680 kWh. In addition, the cleanliness of the manufactured parts was improved and the washing quality increased, according to Bjerringbro.

While “heavy metal” is already difficult, it can be made even worse: hospital wastewater has all the problems of “normal” municipal wastewater, coupled with drug residues, pathogens and antibiotic-resistant bacteria. This is a dangerous cocktail that can hardly be dealt with using conventional treatment methods. The legislation is correspondingly strict: in Denmark, for example, hospitals above a certain size are defined as point sources that must pre-treat their wastewater before it is allowed into the municipal sewage systems — and that's not so easy.

Fighting the Germ: A Modular Treatment of Hospiat Waste Water

Grundfos is breaking new ground at Herlev Hospital in Copenhagen. The water specialists have developed, planned and tested a multi-stage wastewater treatment system over several years at the 1,600-bed hospital. The result: one of the country's most modern wastewater treatments, based on the tried and tested Biobooster membrane that reliably retains all bacteria.

However, since, in contrast to mozzarella production, pathogens and drug residues also have to be separated from the wastewater, ozonation and cleaning with activated carbon is also carried out before — for safety ­reasons — water and exhaust air are treated again with UV light.

In the case of exhaust air, photoion­isation and catalytic treatment are also carried out so that neither pathogens nor unpleasant odours can escape to the outside. This is not unimportant, as the hospital is in the immediate vicinity of residential areas. In this way, 99.9 % of pharmaceuticals and 99 % of x-ray contrast media, as well as bacteria, viruses and hormones, can now be safely retained, Grundfos explains.

Three times water, three times other challenges. Whether it's cleaning up dairy residues, reusing industrial washing water or purifying highly contaminated hospital wastewater: there is a suitable component for every water in the modular system. It’s good when you can count on partners who care about water.

* Contact Grundfos: Phone +45-87501400

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