Cheese on Toast?
Dairy effluent treatment plant refurbishment and operation
One of the UK's largest cheese factories, producing over 60,000 tonnes of cheese a year was having some real issues with its effluent plant.
An aerobic digestion based system with two aerobic tanks feeding two settlement tank (in series) and a final sand filter polish to river, with tight specs for suspended solids and phosphates.
A planned shutdown addressed the main issues with aeration in Tank 1, where a number of aeration tubes had blown off, and a settlement tank that had most of its scrapers missing, as well as major ground works and drainage to the overall site, meant a busy back end of 2021.
The addition of AD biogas waste water added a different flavour to the usual infeed, of indeterminate chemical make up and of unmetered volume and solids content it was a source of uncontrolled variance that had to be managed better.
Added into the mix was new site management, experienced in AD biogas (which was part of the effluent plant) but not in Aerobic systems, meant that in addition to bringing the plant back on line a substantial training programme was needed. Experienced operators had been retained in the new management structure but there was some new blood in their too.
Detailed lab work was required first, MLSS, MLVSS, SSVI, COD feed levels etc were carried out over the period to obtain a baseline of wastewater feed characteristics and to determine optimum F/M levels for each aerobic digester and its settlement tank partner.
The tricky part was ascertaining flow rates where no flow-meters were present, literally no flow measurements were evident across the plant! we added a flow-meter to the infeed pump, fitted tape measures to old V notches and set to work!
Re-seeding the empty aeration tank from the second tank worked well, the settlement tanks were back to brand new (nearly anyway) but it was heavy going, after a period of a few weeks it was stabilised.