Just a few weeks to go: in mid-November, a new SBR plant will start operation in Innertkirchen, a municipality of 1,000 inhabitants in the Bernese Oberland region of Switzerland. Situated at the same location as before, it will replace the existing treatment plant, which has a design capacity of 3,000 PE, has a high proportion of infiltration water and is supplied with oxygen by a surface aerator.
However, it is no longer up to the standards of the best available technology. In the interests of the environment in these beautiful climes, not far from the much-visited Aare Gorge, a decision was taken to make this investment in the future.
Every sludge transport costs money
But back to today: since space is limited at the Innertkirchen treatment plant, the sewage sludge it produces has to be transported by tanker for dewatering at the Meiringen treatment plant eight kilometres away. This makes good sludge thickening all the more important. Every truckload that this can spare saves costs and benefits the environment.
In his search for the best solution, treatment plant manager René Heimann had a competent contact: VTA area manager Martin Lerch. VTA products have long been in successful use in Innertkirchen for phosphate precipitation. On the strength of this positive experience, Mr Heimann was very interested when he learned from the VTA expert that even small amounts of VTA Nanofloc® are enough to significantly improve the sedimentation and thickening behaviour of sewage sludge.
No sooner said than done: after comprehensive analysis of the on-site conditions at the plant, a trial was carried out and a significant optimisation of the settling and thickening properties did indeed immediately become apparent.
There is now less sludge to be transported to the dewatering plant. ‘The lower transport costs mean that at the end of the day, the expenses for VTA Nanofloc® are more than made up for’, says the plant manager in a very positive summary.
Drain values improved once again
But that was by no means the whole story. The dosing point chosen for the addition of VTA Nanofloc® was the ecosystem, and lo and behold: important parameters in the discharge from the treatment plant also improved once again. Although the trial was started in autumn – at a time when the wastewater temperature and biological activity of the microorganisms taper off – full nitrification set in. The drain values for ammonium are now below 1.0 mg/l, and COD also showed further improvement to values below 25 mg/l.
Field report from the VTA Group’s scientific journal “Laubfrosch”, issue 77