Clear water for households

In 2019, during a public tender process, Krones won the contract to deliver an iron removal system for Wasserservice Daibersdorf GmbH in lower Bavaria, Germany. With this first-ever contract with a public drinking water utility, Krones has proven that the technology behind the Hydronomic not only meets beverage producers’ most stringent standards of hygiene and longevity, but the resulting water quality and initial investment also meet the requirements of public utilities.

The municipal waterworks of Wasserservice Daibersdorf GmbH lies amid woods and meadows

The GPS navigation system announces: “You have just arrived at your destination. Get out here and continue the rest of the way on foot.”

This is how it is when one visits a natural spring. This particular spring belongs to the municipal waterworks of Wasserservice Daibersdorf GmbH. The plant lies on an idyllic site amidst woods and meadows, a few hundred metres from Daibersdorf, a hamlet that is home to just a handful of residents. Armin Grassinger, mayor of Dingolfing, and Gerald Rost, mayor of Gottfrieding and representative of the Middle Vils Water Utility special-purpose association, are awaiting the arrival of the Krones magazine team for an interview. Together with them is Markus Schmitz, plant manager for Mittlere Vils Water Utility and deputy director of Wasserservice Daibersdorf GmbH.

From left to right: Armin Grassinger (mayor of Dingolfing), Markus Schmitz (plant manager for Mittlere Vils Water Utility and deputy director of Wasserservice Daibersdorf GmbH), and Gerald Rost (mayor of Gottfrieding and representative of the Middle Vils Water Utility special-purpose association.

Since 2010, this community waterworks had been supplying drinking water from two deep wells to the nearby town of Dingolfing as well as the Middle Vils Water Utility special-purpose association – everyone involved agrees that they have been doing it in “excellent partnership that transcends party affiliations and local boundaries.”

Public tender process
“These two wells, which are 144m and 149m deep, respectively, serve as a second water source. We use them as a backup to ensure our citizens can always rely on a secure water supply,” said Grassinger.

“The municipal utilities of Dingolfing and the Mittlere Vils special-purpose association each hold a 50% stake in the project and likewise each use half of the approved rights to 500,000m3of water per year,” added his counterpart from Gottfrieding, Gerald Rost.

The quality of the water in the two wells is outstanding and meets the strict criteria of Germany’s Drinking Water Regulation (Trinkwasserverordnung). “In terms of its high magnesium and calcium content, it can compete with some high-end mineral waters,” said Schmitz. Under the regulation, iron and manganese levels fell below the limits of 0.2 and 0.05mg/l.

Nevertheless, there was one problem in spite of the excellent water quality: Until now, the water was fed from the two wells directly into the water supply network and the iron and manganese contained in the water left deposits in the water mains and pipes. During local firefighters’ training exercises, reddish-brown water gushed out and residents sometimes had to run their water for several minutes to get clear water.

A hydrogeologist engaged to look into the problem recommended that the wells be retrofitted with an iron removal system. How this works is that iron is first oxidised, converted from a dissolved to an undissolved (solid) state and then filtered using a sand or deep-bed filter. Published in Bavaria’s Official Gazette in early 2019, this was also the project specification for the public tender initiated under the German Construction Contract Procedures (Vergabe-und Vertragsordnung für Bauleistungen – VOB)

First public contract
In an effort to expand its customer base for the Hydronomic water treatment system, Krones participated in a public tender for a public water utility for the first time.

For the first time, a Hydronomic MF water treatment system from Krones is being used by a public utility

“There is a big difference between technical specifications for industrial contracts and those for a public tender,” explained Joerg Berger from Krones’ sales team for process technology, who was responsible for the Wasserservice Daibersdorf GmbH bid. “When you bid on an industrial project, you can negotiate and lower your bid if need be. However, in a public tender, you have to get it right the very first time, doing extremely precise calculations right from the get-go.”

They did get it right the first time: Krones was awarded the contract. The decisive factors were that they fulfilled the criteria in terms of cost-effectiveness, expandability, ease of maintenance, service availability, longevity, and low energy consumption. After the tender ended, construction officially began in May 2019 and the system was commissioned June the following year – somewhat later than planned due to the coronavirus pandemic and the transfer of ownership which took place in September.

“The big advantage in choosing Krones was that they would deliver the system fully programmed,” explained Schmitz. “Otherwise, it is customary in public tenders that electronics are delivered by a second company and programmed by a third. Since everything comes from a single source, interface issues could be avoided.”

Rost sees another advantage,: “Krones was able to deliver a system in V4A-type stainless steel instead of a coated mild-steel so we got the best of the best.”

Built entirely of stainless steel, the Krones Hydronomic meets the highest hygiene requirements.

The Hydronomic MF water treatment system installed in Daibersdorf includes two media filters that run in parallel, each of which is rated at 54 cubic meters per hour

Using pure oxygen to remove iron
The Hydronomic MF water treatment system comprises:

  • Two media filters running in parallel, each rated at 54m3/h
    The stratification of the filter media was selected especially for this purpose and matched to this specific application. Filled about two-thirds full with different layers of garnet, silica sand, and manganese dioxide, the upper third contains raw water, which runs downward through the filter media. To optimise the flow of both filtration and backflushing, filter tanks are equipped with specially-designed nozzles in the bottom.
  • Oxymat oxygen injection system
    The Oxymat injection system is a zeolite-filled adsorber which binds nitrogen from the air to generate oxygen. Unlike conventional systems that use air to remove iron from raw water, this one uses pure oxygen derived from the air. Since the ratio of oxygen to nitrogen in air is 21 to 79%, it takes only around one-fifth the volume of pure oxygen to do the job, which means that iron removal using pure oxygen is more efficient than conventional methods. The oxygen is pumped by way of a Venturi nozzle at the infeed to the filter tank and converts any dissolved iron and manganese into a solid state.
  • Backwashing pumps
    Once a week, the backwashing pumps flush both filters against the direction of filtration flow (bottom-top) with filtered water from the clean water tank to clear the filter sand of built-up iron and manganese flakes. The process takes around 20 to 25m3of clean water and only about 20 minutes.
  • Pneumatic valve technology from Evoguard  
    Employees of the waterworks can take care of maintenance work and seal replacement on these enviro-certified valves themselves. There is no need to call on our service team, another specification we were able to meet.
About once a week, the backwashing pumps flush both filters against the direction of filtration flow (from bottom to top) with filtered water from the clean water tank to clear the filter sand of built-up iron and manganese flakes

More hygienic, long-lived, and expandable
The plant’s yield, i.e. the actual amount of usable water produced, is around 99.5%. Since the temperature of raw water is around 8 to 14°Cand not at risk for microbial growth, additional hot-water sterilisation, which is customary throughout the beverage industry, is unnecessary. Its energy consumption is also low.

“We are certified under DIN ISO 50001 – Energy management systems. A high level of energy efficiency was a key objective and the Hydronomic met it since only the backwashing pump uses an appreciable amount of additional energy,” stressed Schmitz.

“The use of a Venturi nozzle to inject oxygen eliminates the need for an otherwise customary aeration tank, which in turn means no pressure loss. As a result, a much smaller compressor is needed than a conventional aeration-based iron removal system. I think Krones was already geared toward minimising energy consumption through its work with the beverage industry,” he added.

The ability of the Hydronomic to accommodate expansion was another important criterion for winning the contract. In general, the system’s modular design makes it easy to add capacity simply by connecting an additional media filter tank. The system in Daibersdorf is also prepared for the installation of a Hydronomic GAC active carbon filter, “in case we need it later to ensure the necessary water quality,” said Schmitz.

“As you know, drinking water is the most highly monitored commodity,” he says with pride.

“We want to ensure the best possible supply of water at the highest level of quality and safety for our residents in the long -term because we have to be able to meet exacting hygiene standards in hospitals and schools after all. The system’s longevity – a lifespan of 40 to 50 years – was also a key factor. Krones was able to offer us this enhanced standard of hygiene, already established in the beverage industry, as well as a highly dependable supply,” explained a satisfied Grassinger.

Rost can reassure his fellow citizens with a clear conscience: “We have laid the groundwork to provide this basic need and we have not detected any more iron and manganese deposits in our communities’ pipes.”