Low rate

systems have a longer Hydraulic Retention Times which range from two to six weeks and thereby ensure better stability of the treatment process with consistency in the performance of all the units installed in the plant. These systems need large tank volumes because of the longer Hydraulic Retention Times. These are principally chosen for waste streams such as solid wastes, slurries, etc. because, they require longer time for sufficient anaerobic degradation.

The treatment process involves a series of bio-methanisation reactions and hence biogas is produced during the treatment. The process is designed in such a manner that significant reductions in organic load can be achieved and electricity consumption in the downstream processes is reduced due to the same. In addition to this, electricity consumption can also be reduced by using the biogas generated to generate power and using the same to meet a fraction of the total electricity demand.

Plug flow, Batch, Accumulation and Continuously Stirred Tank Reactors (CSTRs) are the most applied examples of the low rate systems.