LEADING instrumentation company, Process Instruments is using particle counters to optimise filter backwashes, reducing the frequency, increasing the quality of the water and saving thousands in reduced energy usage.
Particle counters are used in the UK as a means to identifying potential cryptosporidium oocysts by looking at particles in the size range 4-7um, either post filter or even in a non-filtered supply.
Occasionally but less frequently they are used to optimise a filter before being moved to optimise another filter. Very few plants have particle counters installed on the outlet of every filter.
All this is set to change following pioneering work in America, where plants are being fitted with particle counters on every filter, which are then being used to control the filter backwash. This initialises a backwash based on the quality of filtrate rather than a surrogate measure such as time.
Figure 1 shows a filter being controlled by time and how the filter is put into backwash unnecessarily. This results in reduced quality of water, increased energy usage and greater pressure on the rest of the plant with a greater than necessary volume of backwash water to process.
Figure 2 shows a filter where the backwash is controlled by a particle counter. In this case the filter runtime was extended by 50 per cent and the quality of filtered water was increased. Backwashes were reduced by a third with the consequent energy savings.
Chemtrac Systems Inc is the world premier manufacturer of particle counters for use in water treatment plants and these are available from its distributor in the UK, Process Instruments.
The particle counter PC2400 provides a level of online, continuous monitoring not possible using turbidity measurement.
Dr Craig Stracey of Process Instruments said: “Many companies suffer from excessive energy usage through greater frequency than required backwashes. The PC2400D allows operators to really see what’s happening, and therefore optimise the filtration process with remarkable financial benefits.”
Process Instruments, which operates globally, is based in Burnley, Lancashire and is dedicated to providing solutions to problems in the water, waste, chemical and paper industries. Clients include Georgia Pacific, St Regis, Rhodia, Bristol Water, Northumbrian Water, Urenco and Dow Chemicals.