Aerators boost treatment plant's year-round effectiveness
28 Dec 2021
Landia aerators played an important role in the upgrade by Phoenix Engineering of Yorwaste’s Harewood Whin Leachate Treatment plant to ensure year-round success...
Built in 1990, Yorwaste treatment plant in Yorkshire manages over half a million tonnes of waste annually.
Owing to its age, the plant was predominantly a manual operation, with very little process automation or data acquisition or recording, and no automated pH control option.
Furthermore, its lagoon system was not achieving sufficient biological treatment efficiency during the winter months and the higher strength leachates within the site landfill were a problem for the treatment plant system
The company commissioned Phoenix Engineering to carry out detailed process studies, then design and construct a major refurbishment of the treatment plant.
Phoenix managing director Jonty Olufsen identified the lagoon as a priority for improvement within the project.
“During the winter, the existing mechanical floating aerators meant the lagoon could only operate at around 5°C, when to achieve the most effective biological treatment, it should have been more like 20°C”.
The oval shape of the (1400m3) lagoon made the task more complex, explained Olufsen.
“We worked long and hard with Landia to find the best way to heat the biological mixed liquor and keep it warm during the winter months. It was imperative that the contents of the lagoon would be aerated and mixed properly”.
Four Landia 18.5kW AirJets, comprising a Landia Chopper Pump and venturi nozzle, were installed to provide thorough mixing and aeration, with the chopper knife system ensuring the aerator did not get clogged due to contaminants in the leachate.
During the settlement period of the leachate treatment plant, any movement in the lagoon had to be stopped as quickly as possible before the start of the next cycle to ensure suitable time for settling.
A 3kW submersible propeller mixer from Landia was also installed. This small mixing unit runs for just a short time - only starting up when the AirJets stop. Aimed against the flow, the propeller mixer’s job is to act as a brake, slowing down the movement in the lagoon.
The result, says Olufsen, is three-dimensional mixing. From the previously unsatisfactory temperatures of just 5°C with the old mechanical floating aerators, a consistent temperature of around 20°C is maintained throughout the winter, making the biological process very efficient.
A second lagoon has been converted for raw leachate balancing, allowing for controlled blending of incoming leachates. For both lagoons, full process controls have now been installed, with a new sodium hydroxide storage and dosing system for pH control.
As principal contractor, Phoenix Engineering has installed a new electrical control and automation system with control building, remote IO and control panels. The whole plant was also linked remotely to Phoenix Engineering’s DLOG (digital logbook).
The two companies also worked together to source and deliver new duty/standby pump skids - fabricated, built, and tested at Phoenix Engineering’s workshop, then delivered and installed on site , together with a new gantry arrangement to support new control panels, instruments, and aerators.
