Sludge-to-energy: STP Tiel


STP Tiel


Tiel, The Netherlands




Thermophilic digester volume:
4000 m3

Treatment capacity:
14.5 tonnes of dry matter/day

Biogas production:
1.5 million Nm3/year

H2S removal:
2000 ppm to <40 ppm

Struvite production:
1.2 t/day (40% dry matter)

NAS-ONE® volume:
1,285 m3

Nitrogen load:
440 kg N/day


By order of the Rivierenland Water Board, STP Tiel had to be converted into a 100% energy-neutral plant. Colsen is the technology supplier in the consortium that was awarded the contract for the “Sludge digestion optimisation – Tiel STP” tender. By applying the following technologies, the consortium managed to win the tender on the basis of total cost of ownership.

Applied technology

Thermophilic digestion with DIGESTMIX®

The 4,000 m3 thermophilic digester is kept at a stable temperature of 52 °C, to ensure that sludge is broken down as efficiently is possible. 3 DIGESTMIX® systems keep the entire digester at the right temperature and make sure the sludge is mixed properly.

Biological biogas desulphurisation with BIDOX®

The biogas produced by the WWTP is desulphurised in a BIDOX® system, so that it can be used in the CHP system to produce heat and electricity.

Phosphate recovery in the ANPHOS®

The ANPHOS® reduces the phosphate load from the sludge line to the waterline. In a two-step process, phosphate present in the reject water is deposited as struvite, which can be removed and used as a sustainable fertiliser.

Nitrogen removal via Anammox in the NAS-ONE®

The old mesophilic digester at Tiel STP has been converted into a NAS-ONE® system, which uses anammox bacteria to remove nitrogen with a removal efficiency of >80% TN and >90% NH4-N. The treated effluent that emerges from the NAS-ONE® ends up in the waterline of Tiel STP.