Sludge is an end-product of wastewater treatment. This sludge needs further treatment before it can be used as a product or be disposed off. A wide variety of processes are available to reduce sludge volume and alter sludge properties prior to disposal or use of the treated product.

One can distinguish volume reduction processes, stabilisation processes, and thermal destruction processes. WATERLEAU has developed and engineered technology in each of these three fields.

1. Drying

Drying is the process of transforming biosolids or organic residues into useful products or green fuel. Drying techno logy is not only used for sludge but also for other organic matter with high moisture content such as manure.

Removal of water from sludge improves efficiency of subsequent treatment processes, reduces storage volume, and decreases transportation costs. If circumstances justify removal of water beyond that achievable by mechanical dewatering processes, drying is needed. Thermal drying with direct or indirect dryers is used to achieve near-complete removal of water from sludges.

Advantages

Up to >80% volume reduction

Up to >90% weight reduction to reduce transport and disposal costs

Use of dry product as soil conditioner or fertilizer in agriculture

Use of dry product for renewable energy production

Final product is dry, sanitized, odourless and can be in powder or granular form

Waterleau proposes two types of indirect dryers:

HydroGone® horizontal disc dryer

PuttArt® vertical dryer granulator HYDROGONE® horizontal disc dryer

The choice between both types depends on the desired capacity and the dry solids content of the dried product.

2. Stabilisation

DOT.COMPOST® is WATERLEAU's way of stabilising sludge using lime.

3. Incineration

Sludge incineration is the thermal destruction of sludge by oxidation at high temperature (also known as combustion). Compared to sludge drying, incineration has the distinct advantage of effectively eliminating the sludge.

Only a small inert ash quantity remains.

See also the section on HELIOSOLIDS® in the Waste section.