Sludge cake storage, reclaiming & conveying

The drive during the latter part of the 20th century to clean up the discharge of final effluent into rivers and the sea in Europe and beyond means that sludge cake is now a resource / problem that must safely utilised and disposed. It can also be seen from legislation throughout Europe that putting raw or lime treated sludge cake directly onto agricultural land does not have a long-term future, and land filling of sludge cake is costly and an opportunity lost.

Therefore methods to safely utilise Sludge Cake are major drivers for Waste Water companies across Europe and beyond.

Dewatered Sludge Cake is generally 18 – 35% dry solids, and is a non-free flowing material, that can be variable in it’s mechanical handling properties due to process, location and or season.

Sludge for Advanced Anaerobic Digestion (AAD)

Widely seen in the UK and other European countries, this is a method of treating the sludge cake to generate additional anaerobic activity, boosting energy recovery in Anaerobic Digestion AD plants. There are currently two main technologies employed for AAD –

• Thermal hydrolysis, where sludge is heated to a high temperature under pressure, and then subjected to rapid decompression causing the solids fraction of the sludge to disintegrate.
• Enzymic hydrolysis is where the sludge is broken down into small components which are then acidified, before the material is transferred into the anaerobic digestion plant.

Sludge for Energy from Waste (EfW)

Sludge Cake is used widely in EfW plants and Cement plants as a way to dispose of the material, and when having a high dry solids content, gain beneficial energy. Sludge cake can be combusted when mixed in with other waste fuels or mono-combusted on its own. Drying sludge cake using waste heat allows the sludge to become a valuable fuel.

Sludge for Phosphate Recovery

Recent legislation in European countries means that recovery of Phosphate from sludge is now becoming a driver for change. The main method of recovering phosphate is from the ash of sludge mono-combustion plants, therefore there is a driver to move away from co-combustion of sludge and building new mono-combustion plants.

The drive for building new ways of utilising Sludge Cake tends to mean that projects are delivered as Satellite and Hubs. A number of smaller water treatment works will install sludge dewatering systems and Truck Loading storage silos, with 3 – 5 days of storage on each site. Then a larger water treatment works, with its own large indigenous sludge will install a Sludge Cake Reception and Storage system, that feeds the process, whether that is AAD or EfW.

This reduces costs and enables concentration of sludge and the processing into one larger facility.

We understand the requirements and issues that these clients have and provide robust, flexible systems able to handle the difficult and variable fuels utilised to provide systems that include –

• Reception Bunkers for truck tipping
• Conveying
• High pressure Saxlund Piston Pumps
• Storage & discharge

Having Saxlund as your delivery partner will provide you with proven engineering team, with industry leading technology.