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Reliable phosphate precipitation on the Mosel

Different local authority works cover a supply area with only around 20,000 residents and not only supply water but dispose of waste water too. Thus, the clarification plants of the smaller municipalities ensures the correct disposal of all surface and dirty water fed into the system.

Its waste water treatment removes nutrients such as nitrogen and phosphate because these would otherwise cause excess unwanted growth of plants, such as algae. Even small quantities of just 0.1-0.2 mg/l of orthophosphate as phosphorus (PO4-P) trigger eutrophication. This results in an unwanted increase in damaging plant growth. As the plants die off, excess oxygen from the water is consumed causing an imbalance in the watercourse.

In accordance with EU Directive 91/271/EEC, there are limit values for the introduction of phosphate compounds. Depending on the size of the clarification plant, these vary between 1 mg/l and 2 mg/l Ptotal.

Phosphate compounds are precipitated with lime milk as well as ferrous and aluminium salts. As hardly soluble metal phosphates, they form sediments and are removed from the waste water with the excess sludge.

ProMinent is involved in the storage and metering of the iron(II) solutions needed for the phosphate precipitation. The Heidelberg-based manufacturer provides a complete solution for this in the form of storage and metering system DULCODOS Phos-EL.

Key data:

  • Waste water treatment plants for smaller municipalities with approx. 20.000 inhabitants
  • Phosphate precipitation using iron(II) as the precipitant
  • Compliance with the Ptotal limit values stipulated by EU Directive 91/271/EEC

When replacing the existing phosphate precipitation systems, the local authorities opted for the complete phosphate precipitation solution from ProMinent GmbH.

This decision was prompted by the extensive product range and complete solutions offered by the Heidelberg-based manufacturer, as well as the good cooperation and excellent service received over recent years. With the DULCODOS Phos-EL storage and metering system, as a complete solution, all requirements were fulfilled - and in accordance with the DIBt building inspectorate approval (German Institute for Building Technology). The system was manufactured specifically for the customer from standard components based on the stipulated application and local circumstances, and delivered ready to connect up.

In most municipalities, the storage and metering system designed for outdoor installation comprises a storage tank with a volume of 25 cubic metres, a level indicator, a leak sensor, a filling and metering cabinet with two metering pumps. Depending on the municipality and operator, these are two gamma/ X solenoid-driven diaphragm metering pumps, each combined with a DulcoFlow flow meter. The more powerful gamma/ XL is used in the larger waterworks in the Moselle communities where the output of the gamma/ X is insufficient.

The local authorities received a storage and metering system tailored to their requirements. This task is performed by peristaltic or diaphragm metering pumps. They are characterised by a high control range, a stable delivery rate - even with pressure fluctuations in the system - and safe, wear-free operation. In general, peristaltic metering pumps are also suitable for phosphate precipitation, such as the DULCOFLEX Control - DFXa.

Whether peristaltic or diaphragm pumps are used is the choice of the system operator; both pump types ensure accurate addition of the iron(II) solution for phosphate precipitation.

Process reliability was further enhanced by the redundant (Duty/Stand-by) construction: one pump runs while one is in stand-by. The combination of metering pumps with flow meter DulcoFlow, which is designed especially for measuring pulsating volumetric flows, monitors accurate metering and minimal use of chemicals. All products are simple to use and, because they are easily accessible, can be easily maintained too.

Use of the storage and metering system DULCODOS Phos-EL ensures compliance with the stipulated limit values for phosphate content in waste water. In the near future, chlorine dioxide systems are to be used for potable water disinfection in some waterworks on the Moselle.

Advantages

  • Compact construction
  • Simple installation
  • Enhanced process reliability thanks to: Monitoring of flow and leaks, redundant pump design

Used Products - Reliable phosphate precipitation on the Mosel

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