Desalination in Israel

Peristaltic pumps used at the site

Increased water conservation and water use efficiency are a priority for countries worldwide. A vital process, in a number of countries, is to boost the supply of potable water by desalination. However, large-scale desalination typically requires large amounts of energy as well as specialised, expensive infrastructure, making it very costly compared to the use of fresh water from rivers or groundwater.

The large energy reserves of many Middle Eastern countries, along with their relative water scarcity, have led to extensive construction of desalination in this region. Saudi Arabia’s desalination plants account for about 24% of total world capacity.

Watson-Marlow has a long history of supplying pumps to conventional water and waste treatment plants for metering and dosing the chemicals which are used to remove suspended particles, minerals and contaminants and to maintain pH and disinfect the water. Similar metering and dosing applications are found in desalination processes and sales, to that market, are increasing both internationally and, more recently, in the UK.

Israel has a number of desalination plants which provide about one third of the country’s annual demand of 2 billion cubic metres of fresh water. One of the most recent plants at Palmachim, 30 miles south of Tel Aviv, was designed with Watson-Marlow peristaltic pumps, specified for a range of chemical metering applications.

A total of 30 Watson-Marlow baseplate-mounted pumps are installed at the Palmachim plant, commissioned in 2007. Its control system is based on the Profibus DP communication protocol which is used to operate sensors and actuators (pumps) from a centralised control centre. The timing of the requirement at this site coincided with Leroy Somers’ introduction of the Profibus option for their Varmeca 20 drive unit. Varmeca drives are frequently used on Watson-Marlow 500 and 600 series pumps and, in this instance, enabled the company to supply the sites’ requirements exactly.

The first stage in the process is pre-treatment of the raw seawater, which changes the consistency of the water and is similar to filtration in a water treatment plant. Next the filtered water is pumped through microfilters before it is pushed through reverse membrane filters, at pressures around 65 psi. This removes the salt from the seawater.

The water from the reverse osmosis stage is clean, safe and pleasant to drink. Typically around 50% of the feedwater becomes product water and the remaining 50% is returned to the sea. A post-treatment stage of the product water involves adding some minerals, such as calcium, to improve the taste and stability of the soft processed water. In keeping with other treatment methods, chlorine is also added for cleansing and maintenance of the distribution system.

Since the original 30 Watson-Marlow pumps were installed at the Palmachim desalination plant, a further quantity have been ordered and this order will be fulfilled with pumps from the new Profibus cased pump range, providing easy installation, greater speed control and a smaller footprint.