North West England
Eden Valley Mineral Water Company
Aerated vertical flow reedbed
The Eden Valley Mineral Water Company (EVMWC), based at Armathwaite in Cumbria, treats and bottles locally sourced spring water for sale and distribution into the potable water retail market.
The wastewater generated on site combines two streams: one is process generated, by the regular plant line wash-downs (trade waste); the second stream is made up of foul water from the site.
There is no sewer nearby, and the wastewater must be treated to meet consent prior to discharge to the local River Beck.
The existing wastewater treatment included:
- Blending of the two streams in a tank
- Screening through CopaSac screens
- Treatment by passive horizontal sub-surface flow reedbed
- Treatment by covered lagoon system
The effluent quality is monitored regularly, and any out of spec water is recycled or stored in the lagoon until within consent.
The frequency of out of spec discharges had been increasing, particularly with respect to ammonia. As a consequence, a packaged treatment plant was installed to treat the foul waste prior to blending with the pH adjusted trade waste and delivery to the reedbed / lagoon system.
So far, existing production lines have managed to cope with the production demand, which is increasing at a rate of 15-20% annually. However, it is likely that additional production lines will be needed, resulting in an increase in flow and loads to the treatment system.
On this account, EVMWC requested a refurbishment of the reedbed system to provide added security to their water management and treatment system.
The influent waste stream was characterised by the following average values:
ARM carried out a thorough site survey which identified hydraulic capacity issues linked to the reedbed horizontal flow’s operating aspect, the position of the distribution system and the grade of media. Also, the passive horizontal flow operation limited the load handling capacity.
ARM undertook the reedbed refurbishment, which involved:
- The conversion of the system to vertical flow operation, to improve hydraulic capacity.
- The installation of a new surface distribution system and of an effluent collection system at the bottom of the bed.
- The use of media of slightly larger size.
- The addition of aeration to the reedbed, to maximise the potential treatment capacity.
Additional improvements were also made to the level control mechanism in the lagoon. Operating parameters, such as effluent depths, were optimised and operating instruction provided to the client.
EVMWC had an existing reedbed asset which, due to changes in production loads, was not operating optimally. They also had concerns that the existing wastewater management and treatment system was vulnerable to further planned increased production loads.
The modifications undertaken by ARM maximised the treatment capacity of the existing asset and secured discharge consent achievement against future increases in production loads.