Factsheets
WWTP Houtrust

Year of construction (renovations) 1967 (1988, 1995, 2008)
Site area 5 hectares
Type of treatment Activated sludge, sluggish flow
Treatment capacity (design) 0.39 million p.e. (at 150g Total Oxygen Demand)
Maximum dry weather flow 3,600 m3/hour
Maximum rain weather flow 13,900 m3/hour
Fine bar screens 2+1, bar distance 6 mm
Pre-sedimentation tanks 6, depth 4 m, total surface area 2,106 m2
Activated sludge tanks 2 lines, total volume 34,820 m3

Types of activated sludge tanks

    - Selector Total volume 1,300 m3
    - Pre-denitrification Total volume 660 m3
    - Anaerobic Total volume 6,000 m3
    - Anoxic Total volume 4,600 m3
    - Aerobic Total volume 21,800 m3
Aeration system Fine bubble aeration
Final clarifier / sedimentation tanks 32, depth 3.1 m, surface area 13,048 m2
Nitrogen removal Pre-denitrification + Intermittent nitrification/denitrification
Phosphate removal Bio-P with optionally additional chemicals

Discharge requirements

    - Total Nitrogen 13.4 mg N/l (yearly average)
    - Total Phosphate 3 mg P/l (10-days rolling average)
    - Chemical Oxygen Demand (COD) 125 mg/l (daily average)
    - Biochemical Oxygen Demand (BOD) 20 mg/l (daily average)
    - Total Suspended Solids (TSS) 30 mg/l (daily average)
Effluent pumps (discharge from Houtrust and Harnaschpolder toNorth Sea) 2+1, capacity 26,000 m3/hour, power 3,200 kW
Primary sludge thickening 1+1, total surface area 781 m2
Sludge centrifugal condensers 1+1, capacity 45 m3/hour
Sludge digestion tank 1, volume 9,750 m3
Digested sludge dewatering centrifuges 1+1, capacity 28 m3/hour
Biogas production 4,800 Nm3/day
Gas engines (biogas) / generators (electricity) 3+1, power 1,000 kW (electrical)

Air treatment

    - Chemical gas scrubbers 2, total capacity 47,000 Nm3/hour
    - Biofilter (air from aeration zone) 1, capacity 20,000 Nm3/hour
    - Active carbon filters (sludge loading area) 4, total capacity 12,000 Nm3/hour