Dry versus wet AD

One reason for the limited development on AD on source separated household waste till these years is the fact that source separated household waste was (and is) often not very well sorted, i.e. shows a high level of contamination.

Due to that fact, history is paved with examples of wet AD systems that did not work satisfactorily - or at all - , because they were vulnerable to contaminations. Pumps were clogged, filters likewise.

The size of wet AD plants varies from small farmer plants to plants with a capacity over 100,000 tonnes annually, but it should be remarked that there is a difference in treating waste with 3 % and 50 % dry matter.

After pretreatment the mass is conveyed to a dissolver with mixing of process water; the mass must typically reach 10 % dry matter content. Traps collect glass, stones and metal. Separation of floating materials is often seen (plastic). The hydrolysis dwelling time is typically a few hours.

Wet AD versus dry AD: General Comparison