Hydronomic water treatment system for a municipal water utility

The GPS navigation system announces: “You have arrived at your destination. Get out here and continue the rest of the way on foot.” And that is as it should be when you visit a natural spring. This particular spring belongs to the municipal waterworks of Wasserservice Daibersdorf GmbH. The plant lies on an idyllic site amid woods and meadows, a few hundred meters 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 already waiting when the Krones magazine team arrives for an interview. With them is Markus Schmitz, plant manager for Mittlere Vils Water Utility and deputy director of Wasserservice Daibersdorf GmbH. Since 2010, this community waterworks has 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 – and everyone involved agrees that they’ve been doing it in “excellent partnership that transcends party affiliations and local boundaries.” 

But there was, nevertheless, one problem despite 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. Reddish-brown water was known to come out of the hydrants during local firefighters’ training exercises, 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. Usually the way this works is that the iron is first oxidized, which converts it from a dissolved to an undissolved (solid) state that can then be filtered using a sand or deep-bed filter. This was also the project specification for the public tender that was initiated under the German Construction Contract Procedures (Vergabe- und Vertragsordnung für Bauleistungen – VOB) and published in Bavaria’s Official Gazette in early 2019. 

After the public tender in early 2019, construction began in May 2019. The system was commissioned in June 2020 – somewhat later than planned due to the coronavirus – and final acceptance and transfer of ownership took place in September. “The big advantage in choosing Krones was that they would deliver the system fully programmed,” explains Markus Schmitz. “Otherwise, it is customary in public tenders that the electronics are delivered by a second company and programmed by a third. Here, everything came from a single source, which meant we could avoid interface issues.”

Gerald 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.” The Krones Hydronomic is built entirely of stainless steel and thus meets the highest hygiene requirements.

Using pure oxygen to remove iron

The Hydronomic MF water treatment system installed comprises: 

1. Two media filters that run in parallel, each rated at 54 cubic meters per hour 

The stratification of the filter media was selected especially for this purpose and matched to this specific application. To ensure optimum filtration, the filter tanks are filled about two-thirds full with different layers of garnet, silica sand, and manganese dioxide filter media. The upper third contains the raw water, which then runs downward through the filter media. The filter tanks themselves are equipped with specially designed nozzles in the bottom to optimize the flow of both filtration and backflushing.

2. An Oxymat oxygen injection system

This is a zeolite-filled adsorber that 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 percent to 79 percent, 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 oxidation. The oxygen is dosed by way of a Venturi nozzle at the infeed to the filter tank and converts any dissolved iron and manganese into a solid state.

3. Backwashing pumps

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. The process takes around 20 to 25 cubic meters of clean water and only about 20 minutes.

4. 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 – yet another specification from the tender that we were able to meet.

More hygienic, long-lived, and expandable

The plant’s yield – that is, the actual amount of usable water produced – is around 99.5 percent. Since the temperature of the raw water is around 8 to 14 degrees Celsius and therefore not at risk for microbial growth, additional hot-water sterilization, which is customary throughout the beverage industry, is not necessary here. 

The system’s 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,” stresses plant manager Markus Schmitz. “The use of a Venturi nozzle to inject the oxygen even eliminates the need for the otherwise customary aeration tank, which in turn means no pressure loss. As a result, a much smaller compressor is needed than on conventional aeration-based iron removal systems. I think that Krones was already geared toward minimizing energy consumption through its work with the beverage industry,” he says. 

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,” says Schmitz. “As you know, drinking water is the most highly monitored foodstuff,” he says, not without pride.

“We want to ensure the best possible supply of water at the highest level of quality and safety for our residents for the long term. We have to be able to meet the exacting hygiene standards of 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 expanded standard of hygiene, which is already established in the beverage industry, as well as a highly dependable supply,” explains a satisfied Armin Grassinger. And Gottfrieding’s mayor Gerald Rost can reassure his fellow citizens with a clear conscience: “We have laid the groundwork to provide well for this basic need. And now, there are no more detectable iron and manganese deposits in our communities’ pipes.” 

I think that Krones was already geared toward minimizing energy consumption through its work with the beverage industry. Markus SchmitzPlant manager