§ Mr. Jessel
To ask the Secretary of State for the Environment (1) what reports he has received concerning the presence in water supplies in south-west London of the organism chironomidae; what action is being taken to eliminate the organism; how long he expects elimination to take; and if he will make a statement on how the matter arose and what action he intends to take to prevent a recurrence;
(2) what advice or instructions his Department gives to water undertakings to monitor water supplies to test for the presence of unwanted organisms; whether he considers present practice to be adequate in the light of the existence of chironomidae in water supplies in south-west London; whether he considers Thames Water complied fully with the recommended procedures; and if he will make a statement;
(3) what advice or instructions his Department gives to water undertakings to check their filter beds and other elements in the processing cycle for water supplies against physical objects which might lead to the entry and multiplication of unwanted organisms in the water supply; whether such instructions or advice were complied with by Thames Water in the light of the presence of contaminated water supplies in south-west London; and if he will make a statement.
§ Mr. Howard
My Department has received a report from Thames Water that chironomid larvae are present in the water supply to parts of the boroughs of Hammersmith, Fulham, Hounslow, Kingston, Lambeth, Merton, Richmond, Southwark and Wandsworth supplied from the Hampton treatment works.
Thames Water found that two sand filters were passing larvae into the supply. These filters have been isolated for inspection and, if necessary, repair. Thames Water is also draining and cleaning the filtered water storage tank at the works. This cleaning operation is expected to take several days to complete. Thames Water is still investigating the cause of the incident.
My Department has not issued specific advice on the monitoring of water supplies or the checking of filter beds for the presence of unwanted organisms such as chironomidae. It is the water undertaker's responsibility to check that processes are operating efficiently and to monitor the quality of water entering supply. My Department's standing committee of analysts has published methods of biological sampling for macro-invertebrates which includes chironomidae. I understand that many water undertakers use these methods to monitor certain water supplies at times of the year when the presence of chironomidae is possible.
My Department will urgently review current practice with water undertakers when the cause of this incident is known.