 The parasite was detected on June 24 and, following consultation with health and local authorities, a notice to boil drinking water was issued for more than 100,000 households and 250,000 people served by the plant. About 500,000 litres of bottled water were also distributed.
A decision to install UV led to seven systems – including two validated UV systems from atg UV Technology – being installed by the end of the weekend following the initial discovery. A week later, all water being produced was free from Cryptosporidium.
The UV systems are automatically wiped and lamp output is monitored using a specifically designed UV monitor camera. The power of the UV lamp is adjusted automatically to ensure the correct UV dose is delivered to the water. The units are capable of being controlled locally or remotely by SCADA. The system adjusts automatically for lamp ageing and changes in the transmittance of the water to deliver a constant UV dose.
The units were installed in line into a 24-inch main. The design avoids bends that would be detrimental to system performance. Lamps can be changed online and the automatic wipers maintain the optical path, ensuring optimum performance, protecting Anglian Water from future Cryptosporidium outbreaks. |