DESCRIPTION

Technical Description

Depth filtration with sand filters and ion exchange are key unit operations in water treatment. CE 582 enables these two operations to be demonstrated.

The raw water is pumped from above into a sand filter. Solids are captured and retained as the raw water flows through the filter bed. The filtered water emerges from the bottom end of the sand filter and then flows through two ion exchangers (cation and anion exchangers). In the process, unwanted ions are exchanged for hydrogen and hydroxide ions. The raw water is softened and desalinated. The sand filter and the two ion exchangers can be used in combination or separately. The solids deposited in the sand filter result in an increase in pressure loss. Backwashing cleans the filter bed and reduces the pressure loss. The ion exchangers can be regenerated with acid or caustic.

The sand filter is equipped with a differential pressure measurement. There are also several pressure measuring points along the filter bed. The pressures are transmitted to tube manometers via hoses and displayed there as water columns. This can be used to plot Micheau diagrams. The flow rate, temperature, conductivity, differential pressure and system pressure are measured. The flow velocity in the filter bed (filter velocity) can be adjusted. Samples can be taken at all relevant points. E.g. diatomite can be used to produce the raw water.

A software program is provided to control the operating states and measure data. A process scematic shows the current operating states of the individual components and the measured data.

The well-structured instructional material sets out the fundamentals and provides a step-by-step guide through the experiments.

Learning Objectives / Experiments

- familiarization with the fundamental principle of the unit operations depth filtration and ion exchange
- observation and determination of pressure losses in a sand filter
- plotting of Micheau diagrams
- principle of backwash
- identification of the different modes of operation of cation and anion exchangers
- regeneration of ion exchangers