Sludge treatment reed beds (STRBs) are an alternative low energy, lower cost solution to managing sludge compared to traditional mechanical dewatering processes such as belt presses and centrifuges.
The technology essentially involves using a series of vegetated gravel reed beds to passively dewater and mineralise sludge on-site. Sludge treatment reed beds have been successfully used in Europe for several decades, with a number system operating for many years treating sludge from sewage plants from 20,000 –250,000 EP.
Compared to mechanical dewatering processes, sludge treatment reed beds afford whole of life costs that are 20–50% lower, 90% lower energy demand, a 50% reduction in final sludge volume, and substantially less operational input required.
The Water and Carbon Group has partnered with the Danish engineering company Orbicon who are the leading international specialists in sludge treatment reed beds and have completed over 30 projects in Europe and the UK since 1995.
Key benefits of using reed beds to manage sludge
- OPEX costs estimated to be 70% lower than belt press or centrifuge technology;
- Power requirements 90% lower than belt press or centrifuge technology;
- Final dry solids content of 25–40%; = reduced volumes for transportation compared to other dewatering technologies;
- No chemicals used for dewatering – reduced operational handling risks;
- Significant opportunities for sludge reuse given that no flocculation chemicals contaminate sludge and higher dry solids content allow for better handling;
- Mineralisation of hazard organic compounds; sludge treatment reed beds offer treatment and dewatering, whereas belt presses/centrifuges only provide dewatering;
- A higher filtrate quality of the water is produced from sludge treatment reed beds than filtrate produced from belt presses; reducing internal load on WWTP Sludge loading if recirculated;
- Opportunities to use on a range of sludge types including some chemical sludges, and;
- Design life >30–40 years (Most mechanical systems have a maximum 15–20 year life).