Alfa Laval AquaProtect technology keeping prisoners safe and secure

A new hot water installation based on Alfa Laval AquaProtect technology is providing a French prison with lashings of hot water on demand while eliminating the risk of Legionella and other bacterial infections. Like any large residential building, a prison needs copious volumes of hot water for its inmates.

Some estimates put the figure required in excess of 160 litres of hot water per inmate per day. Heating, storing and distributing this hot water is energy intensive and, if done inefficiently, can risk the growth of bacteria such as Legionella – the root cause of Legionnaires’ Disease. San Quentin prison, close to Lyon, has overcome both of these problems by replacing an antiquated and potentially dangerous, domestic hot water system with five AquaProtect, anti-Legionella tap water systems from Alfa Laval.

Built in 1991, Saint-Quentin is home to 372 inmates. Its original hot water system was struggling to cope with demand and the pipe-work that delivered hot water to the sports hall, shower facilities, kitchens, working areas and offices was in poor condition. More significantly, there was no system for water treatment or maintenance and water quality was rarely checked. Since the pipe-work urgently needed replacing, the governors of the prison decided to use it as an opportunity to upgrade the complete domestic hot water system.

Safe and reliable system
After a public tender process, a leading French contractor was awarded the contract to install a new tap water heating system in the prison. They chose Alfa Laval’s AquaProtect tap water system because it is safe, reliable and eliminates the risk of Legionella infection.
Enclosed, warm storage vessels, blind spots in pipework and water systems containing stagnant water provide an ideal envi¬ronment in which Legionella bacteria can flourish, particularly if sludge, sediment and scale are present for them to feed on.

Legionella bacteria multiply more rapidly at temperatures between 20°C and 45°C. Hot and cold water systems in institutions and large buildings are major sources of Legionella bacteria, which cause the life-threatening pneumonia known as Legionnaires Disease.

The AquaProtect system solves this problem by continuous thermal dis¬infection of incoming and circulating water to provide Legionella-free domestic hot water. The system consists of five AquaProtect units, each with a reaction and storage tank. Its compact size saves valuable space in the boiler room.

AquaProtect is a plug and play system, so installation is quick and easy. Once installed, it needs very little maintenance. No additional energy is required to provide thermal disinfection since an integral heat exchanger recovers sufficient energy for the purpose. Consequently, the system is extremely energy-efficient. It becomes more so when connected to “free” energy sources such as solar or heat pumps.

How the system works

AquaProtect employs two heat exchangers. The first is connected to the heat source and is used to disinfect water at 70°C. The second heat exchanger is used to cool water from 70°C down to the temperature required at the tap (normally 60°C) and to pre-heat incoming and circulating water before it enters the first heat exchanger. (see schematic)
Once heated to 70°C, the disinfected water needs to be maintained at this temperature for a given period of time to ensure eradica¬tion of any bacteria. Dwell times are generally determined by local legislation. San Quentin opted for a system with a reaction tank (A) and a storage tank (B) to ensure the correct holding time. The reaction tank has an internal configuration that controls the direction of the flow, thereby uniform temperature dispersion and disinfection.

From the reaction tank, disinfected water flows to storage tank B where it is stored until there is a peak demand period. Disinfected water flows from this tank to the second heat exchanger to be cooled ready for distribution.
A mixing valve (C) mixes the dis¬infected water from the storage vessel at 70°C and the cooled, disinfected water coming from the second heat exchanger  to ensure that all of the water entering the network.

For further information,  contact:
Peter Rose
Marketing Manager UK & Ireland
Alfa Laval Limited
Doman Road,
Camberley, Surrey.
GU15 3DN

Phone: 01276 413632
E-mail :peter.rose@alfalaval.com