introduction

SUEZ has been developing its own sludge thickening and dewatering machines; therefore, the Company can offer a comprehensive range of dynamic thickeners (see sludge thickening) and belt filters. This range has been designed to process both hydrophilic type sludge that cannot tolerate high pressures and hydrophobic sludge that can take high pressures in order to produce high dry solids contents. Obviously, the mechanical structure of these machines must be compatible with the belt tensions (pressure) used.

These filters are extremely widespread for a number of reasons:

• very easy to operate and sludge undergoing dewatering easily checked;
• moderate investment and operating costs;
• machines designed with integrated pre-thickening for treating very dilute sludge extracted straight out of the aeration tanks;
• process and filter belt wash continuity;
• simple mechanics;
• produces easy-to-shovel sludge.

Additionally, these filters represent an almost universal process (all sludge types) and are the least energy-hungry of the dewatering processes:

• belt filters: 10-25 kWh · t^–1 of suspended solids;
• classic filter-press: 20-40 kWh · t^–1 of suspended solids;
• centrifuge: 30-60 kWh · t^–1 of suspended solids;

However, the resulting cakes will be wetter.