Mischler, J-F., Bucher Unipektin AG(free)
Biosolids reuse is in a lot of countries based on land application. In most countries hygienization of sludge was not mandatory but SARS-CoV2 pandemic induced a sudden revision of agricultural reuse legislation. In many countries’ sludge hygienization is now mandatory. This could be achieved by many ways but the old way, using lime, might be in some cases the easiest and cheapest way.
Iron chloride and lime conditioning on chamber filter press was mostly abandoned as conditioning in favor of centrifuge and organic conditioning with polymer. The main reasons are the ease of use and the low initial investment of centrifuges.
On a global life cost point of view hygienization approach with pre- or post-liming on centrifuge or beltpress is quite costly as polymer and lime are required.
With Bucher Press it’s of course possible to make a very efficient post liming (less water = less mass to heat up with quicklime dosing) but it’s also possible to run the HPS like a chamber filter press with mineral conditioning only.
The benefits in term of performances with Bucher press allows in most cases to keep sludge evacuation levels to similar figures than with a polymer conditioning despite the 20 to 30% lime addition.
Operation in Nice and Divonne les Bains showed at industrial scale that dewatering performance increase linked to liming is so high that evacuated sludge amount is only 5% higher than with Bucher press and polymer only!
The HPS performances and the requirement to have sludge hygienized might make this old-fashioned conditioning trendy again for agricultural reuse at low opex and low Total Cost of Ownership.
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