Energy plant - WWTP 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

Thermophilic sludge digestion
Biogas treatment
Phosphate recovery
Sidestream treatment


By order of the Rivierenland Water Board, WWTP Tiel had to be converted into a 100% energy-neutral energy plant. Colsen is the technology supplier in the consortium that was awarded the contract for the “Sludge digestion optimisation - Tiel WWTP” 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 WWTP 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 WWTP.


Slibgisting Tiel

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Boris Colsen, Managing Director