61 Mr. Gresham Cookeasked the Minister of Housing and Local Government what steps are being taken to clear the present high level of pollution in the River Thames at London, particularly from the southern outfall sewage works.
§ Mr. Denis HowellReporting on their investigations over the period 1951–61, the Pippard Committee on Pollution of the Tidal Thames noted that when they were appointed the Thames estuary down to Gravesend was in a badly polluted and frequently offensive state. Hydrogen sulphide was evolved through the activity of sulphate-reducing bacteria when the water was completely deoxygenated. They concluded that the aim should be the prevention of offensive conditions together with a margin of safety. They thought that the improvements then being made at sewage works might be enough to prevent objectionable smells but were unlikely to proved a reasonable safety factor, though it was premature to suggest additional work for that purpose.
148WSince then many millions of pounds have been spent on the improvement of discharges; for the past three years oxygen has been present throughout the length of the river; and fish have been caught in reaches from which they had been absent for many decades.
The safety margin is not however considered to be adequate yet. Large scale improvements are still in progress and others are planned.
In the past few days this steady improvement in the river has been interrupted by an unfortunate combination of circumstances.
Owing to the prolonged dry weather the flow of the River Thames has been at its statutory minimum for the last six weeks and at the end of last week the level of dissolved oxygen was much lower than normal.
The G.L.C.'s Southern Outfall Sewage treatment works at Crossness, Bexley, is discharging a good quality effluent but became overloaded with sludge last week. This difficulty has been associated with modifications in operation of the treatment plant which were intended to promote an improvement in the Thames 149W in the long-term. The modifications have been successfully operated during the summer. But they produce larger volumes of sludge for disposal and on several occasions recently the sludge vessels failed to collect the sludge, because of labour difficulties and fog. The accumulated sludge had begun to smell and, if it had not been shed, would have seriously impaired the operation of the Crossness works. The port of London Authority therefore agreed to allow the discharge of the sludge in strictly controlled conditions, on the high ebb tide when the sludge would be most likely to be taken out to sea. The discharge started towards the end of last week and ceased early yesterday. Most of the excess sludge has now been removed; and the G.L.C. have hired extra shipping to take more away to sea. The Crossness works is now returning to normal.
The P.L.A. have offered the use of their dredging hoppers to the G.L.C. The Central Electricity Generating Board are co-operating by suspending the discharge from Battersea "B" Power Station and are increasing the generation of aerated water at Belvedere Power Station.
The oxygen resources of the river have not been exhausted and it has accepted the additional pollution without smelling or killing fish. The high winds, which increase the river's oxygen absorption, have helped in this direction; whether all ill effects will be avoided will depend very much on the weather over the next few days.
The P.L.A. and the G.L.C. are continuing their close monitoring control and propose a general survey of the river tomorrow.
I can assure hon. Members that there is no danger to public health.