1. Background

A water supplier operates several waterworks sites in Germany which extract raw water from the bank filtrate of an adjacent river. The company manages over 300 wells for this purpose.

2. Measurement requirements

The greatest energy losses at waterworks occur with raw water extraction. This generally results from the losses of pumps and built-in components, as well as from iron ochre deposition affecting the wells. Iron ochre sedimentation comes about over time through water delivery and effects of oxidisation. This reduces the yield of a well and with it the usable service life.

The water supplier had replaced many of the wells over a number of years. The development of the specific capacity of a well in operation over time is monitored to assess its economic efficiency. The customer required appropriate measuring technology to enable monitoring of the wells as a function of output. This technology needed to not only measure output but in particular the negative pressure for water delivery. The operator was also in search of robust instrumentation to reliably determine the fill levels in the water extraction wells. This would serve as an important indicator to assess the degree of iron ochre deposition.

3. KROHNE solution

To measure the groundwater level in the wells, KROHNE supplied the customer with the OPTIBAR LC 1010 submersible hydrostatic level probe. The probe was lowered into the well for installation on the cable using a guide tube. The submersible level probe is equipped with a ceramic diaphragm which is particularly stable over the long term and resistant to wear, water hammering and mechanical stresses. It also withstands brief immersion below the surface of the water, something that may happen on installation or after cleaning. No offset drift comes about here.

The OPTIBAR P 1010 additionally monitors the delivery pressure of the well pumps. This ultra-compact pressure transmitter is a highly cost-effective solution for simple process pressure applications that is nonetheless stable over the long term. Featuring IP68 ingress protection, the OPTIBAR P 1010 is the perfect choice for use in water extraction wells and pits. Its recessed stainless steel diaphragm ensures that the pressure transmitter is robust and resistant to overpressure and corrosion.

The measurement data are transmitted to the LS42 battery-powered data logger together with the flow rate values. It wirelessly transmits all measured values to the customer's control room in line with the mobile telecommunications standard. To this end, the data logger features two analog inputs, enabling supply of the 2-wire pressure transmitters and transfer of their data.

4. Customer benefits

Monitoring of the groundwater level and pump pressure along with output results in efficient groundwater management for the water supplier. The measurement data allows the operator to determine the status and track the degree of iron ochre deposition of his wells over time. It is thus possible to take action in good time to specifically regenerate individual wells. Energy-efficient operation of the wells is thus ensured for the water supplier on a long-term basis.

Besides pressure transmitters, KROHNE also offers an extensive portfolio of measuring technology to cater for all equipment needs of water engineering plants. KROHNE supplied the measuring and transmission technology for the water extraction wells (incl. the battery-powered water meters) from a single source.