Where there's muck there's automation
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TANKER OPERATORS have recently been bidding for a threeyear sludge disposal contract with a difference from Yorkshire Water Authority.
For years the work of taking away sewage from Leeds' main treatment plant at Knostrop has been an essential service provided by hauliers. It was a simple operation in which lorries turned up for the muck, were loaded by the driver until half full, fully loaded, or maybe even overloaded, and then driven off for disposal on nearby farms or at sea.
When the new contracts start on July 1, each lorry belonging to contractors Progressive Waste Disposal and DC Cook will be weighed on the first unmanned weighbridge to be approved for trading purposes. The approval was accompanied by much local excitement and a visit by Department of Trade dignitaries from London.
The Knostrop system is selfcontained and illustrates a growing trend towards automation.
Knostrop works needs to get rid of 160,000 tonnes of domestic and industrial waste each year. Last year 97,000 tonnes, including all the industrial sludge, was hauled down the M62 to Goole for disposal at sea. The rest was put onto, or more commonly into, fields within a 10-mile radius of the plant.
Disposal is expensive in absolute terms, getting on for £1 mil lion. More importantly perhaps as it affects cost control, it takes up one fifth of the total budget for sludge treatment. The sludge has no commercial value whatever, as the farmers pay nothing for it.
Yorkshire Water decided it wanted closer supervision of what was being taken out by contractors. Occasional checks were made by taking vehicles to a public weighbridge, but otherwise the authority had no control over the operation.
Under the new system the authority will know when its lorries are going out full, and that it is paying exactly for what is being taken out. The computerised weighbridge will record details about the lorry taking each load out, the date and time of weighing, and, in the case of sludge to be put on land, which field it is to be dumped on.
The land disposal operation needs to be flexible in operation if it to be efficient and cheap. The operator wants to be able to come and go when the work can be fitted in with other schedules.
Only arable land is used for disposal, and then only when it is not under crop. Disposal can only be done when the farmer is willing to take the sludge. Land disposal goes on throughout the year, but in practice there is peak demand during August and September, when crops have just been cut. There can be severe troughs during severe winter weather.
During peaks, lorries can be working on the contract from early in the morning until late at night. Union resistance to manning the weighbridge outside working hours, together with the cost of basic staffing and overtime payments, steered Yorkshire Water towards an unmanned weighbridge.
A complete weighing system meeting strict Department of Trade regulations was installed by Birmingham firm W. and J. Avery. It is sited about half a mile from the loading area and administrative offices.
The system cost around £40,000, half of which was for the weighbridge and half for the automation needed for opera tion without staff to DoT requirements.
A 1 5-metre weighpad is closely surrounded by static barriers on either side and lifting barriers at the front and rear. This is to ensure that the system cannot be fiddled — that it is not corruptible, to use DoT jargon.
A vehicle cannot be half on and half off. A Portakabin adja
cent to the weighpad houses a microcomputer linked to a visual display unit, keyboard, printer, and card reader. A separate record of each wiehging is taken directly from the weighpad, again to meet DoT standards.
The system is operated entirely by the lorry driver, so that Water Authority managers need only look at the print-out. Lorries arriving at Knostrop to collect loads are first weighed empty. The driver takes the vehicle over a sensing pad, which activates the weigher. The weighbridge is zeroed, to take account of any snow or other weight which may be on the pad, and the rear barrier is raised.
Having driven onto the pad, the rear barrier comes down and the vehicle is weighed. The driver gets out of his cab and into the Portakabin, where he feeds in a vehicle identification badge similar to a credit card. This gives details of the vehicle and the operator. If the tare weight of the lorry and the weight on the weighbridge do not roughly match, the front barrier will not lift and the vehicle will be unable to move.
The driver then drives a mile to pick up his load (he does the loading himself) and returns to the weighbridge, where he repeats the weighing procedure. Additionally, drivers with Progressive, which has the land disposal contract, insert a card giving the field reference into the reader. The driver then receives full details of the load The weighbridge system is now being used informally by contractors, but its use will be mandatory when the new contracts come into operation next month. Initial teething problems have been largely ironed out although some operational adjustments, relevant to any weighbridge installation, have been made following suggestions from contractors.
The turning circle for lorries is to be widened. It is adequate for eight wheelers, but very tight for artics at present — which is good for tyre manufacturers but not for the operators. A telephone link has been installed in the Portakabin, so that drivers can easily keep in touch with their managers.
A storage tank is to be put next to the weighbridge, from which the driver will be able to pump off sludge if he is overloaded without having to move off the weighbridge and return to the loading area. That would involve a delay which the contractors can ill-afford on a keenly contested contract, and drivers on bonus payments can well do without.
The Water Authority is anxious to protect its public image, and overloading is something it is keen to avoid, particularly now that lorries are so much in the public eye.
"We have said to our contractors that the maximum weight must never be exceeded," Leeds area manager Mike Sambidge told me last week.
The contract for muck disposal on land, which was won by Progressive against seven other bidders, includes not only haulage from the works but also disposal on land. Land disposal is an option which is more expensive for the authority because the sludge needs more processing. But it is gaining popularity because of environmental pressure against sea dumping, particularly from the European Economic Community.
Anticipating renewal of its contract next month, Progressive is investing not only in road tankers, but also agricultural tractors and equipment. There are two common forms of land disposal. One involves surface spreading, which is relatively cheap but often smelly. The other is a sophisticated from of injection, which is virtually smell-free. Surface spreading can be done direct from the lorry, but for both forms of disposal on land the sludge is normally pumped into a field tank.
While the Leeds area of Yorkshire Water uses contractors for disposal from the main Knostrop works, it uses its own vehicles to do some routine disposal from 17 minor stations in the area.
Contractors are used because they can take on work at unusual hours and can more readily take on temporary drivers for peak hours, Mr Sambridge said. But for milk runs, where lorries serve a large number of small sites, own-account operation was no more expensive and could be cheaper, he said.
Yorkshire Water Authority is well pleased with the unmanned weighbridge because it can keep close control on its disposal costs with minimal effort. The system at Knostrop is, however, automation at its most basic.
According to Avery, the potential to build into unmanned weighbridges a much more complicated system of computerised loading, invoicing, accounting and stock control is just beginning to be realised by major transport users. Blue Circle plans to open a computerised system of loading on a weighbridge, which should rule out any possibility of significant overloads. The system will be linked to a central computer, and will be operated by cards issued to drivers.
At Winsford, ICI has recently opened a similar system for weighing on an unstaffed weighbridge, using an information card.
The automation of weighing makes the operation simpler, easier and quicker for the shipper. Whether or not it will benefit the contractor or haulier is another matter.