In district heating networks, power plants, process facilities, or industrial battery production, water is not merely an operating medium – its purity determines the efficiency, reliability, and longevity of the entire system. If a stationary treatment system fails at short notice, or if large quantities of ultrapure water are temporarily required for overhauls and commissioning, asset and operations managers must react quickly. Mobile water treatment plants are then the instrument of choice, as they immediately supply ultrapure water of standard-compliant quality, thus protecting against costly damage from corrosion or scale formation.
This article is aimed at asset and operations managers for heating and energy networks, as well as HVAC professionals and building services planners. It explains the capabilities of modern trailer systems, categorizes the relevant standards (especially VDI 2035 and AGFW FW 510), and shows step-by-step how to plan projects and emergency operations using mobile treatment. Additionally, it explains the role of sustainability and Total Cost of Ownership, and how to fulfill documentation and audit requirements.
Heating and process systems rely on a continuous supply of demineralized or deionized water. In the event of unexpected disruptions, production downtime, pressure drops, or thermal overload are imminent. Mobile water treatment plants step in when:
Without adequate water quality, high costs are threatened by scale deposits and corrosion. Studies show that even one millimeter of scale reduces heat transfer by approximately 9% . Such losses accumulate over the lifetime of a system, leading to high energy costs and potentially jeopardizing manufacturer warranty claims. Mobile systems counteract this.
The decision for mobile water treatment is based on several factors:
ORBEN's trailer fleet comprises three basic models that can be combined:
Since the trailers can be combined, capacities of up to 120 m³/h To implement. For smaller applications, ORBEN offers jumbo cartridges for 12,000 to 22,000 l/h; for mobile projects with a runtime of five days or more, the use of trailers is recommended.
The high water quality is achieved through several coordinated stages:
Thanks to this modular design, the trailers are suitable for demineralized water according to VGB/VdTÜV and meet the requirements of VDI 2035 and AGFW FW 510.
For the trailers to operate optimally, certain limit values must be observed:
The systems can be connected to raw water pipes of various diameters (DN 50 to DN 100). For power supply, depending on the model, 10 to 70 kW as well as 230 V or 380 V are required.
Beyond emergencies, the trailers can also be used for months or years. This is useful when investing in a stationary plant is not economical or long-term construction sites require a flexible solution. According to ORBEN the trailers, thanks to modern technology, consistently deliver high water quality over longer periods and avoid high capital costs for building new systems.
For long-term projects, the service team can monitor the systems, replace resins, and perform maintenance. A combination of several TR‑30 and TR‑60 units thus enables the supply of entire city districts with district heating.
The VDI 2035 guideline is the central set of regulations in the heating industry for preventing scale formation and corrosion-related damage. The current version from March 2021 (Sheet 1) replaces older versions from 2005 and 2009. Among other things, it regulates the following parameters:
VDI 2035 specifies these parameters in tables depending on heating capacity and system size; it distinguishes between low-salt and high-salt operation. For low-salt operation, the following apply: conductivity 10–30 µS/cm, pH 9.0–10.0, oxygen < 0.1 mg/L, total hardness < 0.02 mmol/L. For high-salt operation, the guideline values are 30–100 µS/cm (semi-saline) or 100–1500 µS/cm (saline), the pH range is 9.0–10.5; the oxygen content may be < 0.05 or < 0.02 mg/L respectively. The guideline emphasizes that adhering to these values minimizes damage.
The German Association for District Heating (AGFW) has published the worksheet FW 510 in addition to the VDI regulations for district heating networks. It distinguishes between low-salt, semi-saline, and saline circulating waters and sets limit values for conductivity, pH, oxygen, and water hardness. The values largely correspond to the tables mentioned in Section 3.1. Since district heating networks are often large-scale and combine materials such as steel, copper, and aluminum, these specifications are essential for operational safety.
For asset managers, this means:
In the context of the energy transition, new industries are emerging: electrolyzers for hydrogen production, lithium battery manufacturing, and semiconductor production require ultrapure water with extremely low conductivity. DIN 19628 defines the requirements for water used in electrolysis plants; low conductivity (often < 0.1 µS/cm) and an almost complete absence of ions and dissolved solids are crucial. DIN 3696 describes ultrapure water qualities for laboratory and medical applications, where only trillionths of ions are permitted. Mobile systems combining reverse osmosis, degassing, and mixed-bed ion exchange achieve these qualities and can be used, for example, during the commissioning of electrolyzers.
Untreated or improperly treated water leads to deposits and corrosion processes. These risks are severe for district heating networks as well as for industrial heating circuits:
Compliance with guidelines is not only a technical but also a legal requirement. Manufacturers of boilers and heat exchangers often demand adherence to VDI 2035 as a condition for their warranty. Those who disregard the reference values risk losing warranty claims. Furthermore, energy supply contracts may include conditions that are increased in the event of high conductivity or corrosion damage.
An operational interruption due to leaks or heating system failure causes high costs: repairs, production losses, and potential contractual penalties quickly add up. The expense for proper water treatment – i.e., renting or operating a mobile plant – is comparatively low.
Mobile trailers can be used preventively to minimize risks. During commissioning, the system is first flushed with ultrapure water to remove welding residues, oil, and dirt. During an overhaul, the trailer replaces the stationary demineralization plant, ensuring the network remains filled in accordance with standards. In the event of failures, it allows for a response within a few hours, preventing corrosion damage. The integrated measurement technology continuously documents conductivity and pH value; these data serve as proof for audits and inspections.
A common criticism of ion exchange processes is resource consumption. However, ORBEN operates Europe's largest regeneration plant and relies on reusable resins, which are cleaned and reused after use. The plant regenerates up to 40 000 L of resin daily and supplies around 10 000 customers. The resin is cleaned, reloaded with acids and alkalis, and then filled into cartridges. Each cartridge receives a batch number and a filling date; the results of quality checks are 100% documented and traceable.
The plant uses Rhine water for rinsing and returns it to the river after purification. This means no municipal water is consumed, and the ecological footprint is reduced. For operators, using regenerated resins means less waste and lower procurement costs.
Mobile trailers minimize the need for stationary backup systems. Instead of building multiple demineralization systems in parallel that are rarely used, trailers can be rented as needed. This reduces capital commitment and shrinks operating areas. The modular combination of units (TR‑10, TR‑30, TR‑60) allows for precise configuration without over-dimensioning.
During operation, the service team monitors the resins and replaces them as soon as the breakthrough conductivity is exceeded. Since reusable resins are regenerated, ongoing operating costs are significantly lower compared to single-use resins.
The TCO approach considers not only acquisition costs but all costs over the entire lifecycle – maintenance, operation, downtime, energy losses, and disposal. Mobile water treatment has a positive impact by:
The production of green hydrogen through electrolysis requires extremely pure water. Impurities can damage the membranes and catalysts in electrolyzers or reduce their efficiency. DIN 19628 defines the specification for electrolysis water; it requires an electrical conductivity in the range of a few microsiemens per centimeter and a minimal concentration of dissolved ions. ORBEN's trailers, combining reverse osmosis, degassing, and mixed-bed ion exchange, achieve this quality (conductivity < 0.1 µS/cm).
The trailers can be used during the commissioning of electrolysis plants to perform initial flushing, fill tank farms, or serve as a backup if the stationary ultrapure water generation fails. The modular capacity also allows for the supply of larger clusters of electrolyzers.
The manufacturing of lithium-ion batteries and semiconductor chips requires ultrapure water according to DIN 3696. In such applications, the water may only contain traces of ions and organic components. Mobile units are suitable when pilot plants are being ramped up or when short-term expansions are planned. Since the trailers can be integrated into cleanroom processes, highly pure water can be supplied without interrupting production.
The VDI standard requires complete documentation of all fill and make-up waters. In practice, this means:
Modern trailers feature integrated sensors; the data can be digitally recorded and transferred to management systems. Alternatively, mobile measuring devices (conductivity and pH meters) can be used.
Mobile water treatment plants are a strategic tool for asset and operations managers in district heating networks, power plants, process facilities, and future industries such as hydrogen or battery production. They deliver ultrapure water of standard-compliant quality within the shortest possible time, bridge outages, support overhauls, and enable flexible project planning. Thanks to their modular design, capacities from 10,000 to 120,000 l/h can be achieved.
Compliance with VDI 2035 and AGFW FW 510 guidelines is essential: Only with correct conductivity, pH value, and minimal oxygen content can corrosion and scale be prevented. The VDI 2035, updated in 2021, indicates that modern systems aim for low-salt water with conductivities of 10–30 µS/cm and keep oxygen content as low as possible. During planning, it is crucial to know the raw water condition, select suitable trailers and connections, integrate metrological monitoring, and train personnel.
Sustainability plays a central role: Through reusable resins and an efficient regeneration station, resources are conserved, waste is reduced, and TCO is optimized. Mobile systems avoid high investments and create flexibility for short-term demand peaks.
In summary, mobile water treatment offers operational reliability, standard compliance, and sustainability all in one. For asset managers, this means a reliable option to actively shape the energy transition with stable heating networks, efficient process facilities, and durable infrastructure.
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