Combining thermal hydrolysis with drying and downstream thermal processing to optimize energy recovery from sewage sludge

Abstract

Thermal hydrolysis of sewage sludge prior to subsequent anaerobic digestion is a well-established process with nearly 90 facilities worldwide. Cambi, the market leader, has two thirds of the installations, ranging in size from 11 – 450 metric tons dry solids/day.

The majority of plants are combined with land use of the biosolids as a low carbon fertilizer, due to the biosolids meeting Class A standard under the US EPA 503 regulations. In addition, the dewatered biosolids are friable, have low odor and high dry solids which make it a desirable product.

However, there are instances where land application is limited due to regulations or topography, or clients have existing thermal infrastructure and want to maximise its use. The aim of this paper is to demonstrate how combining thermal hydrolysis with digestion prior to thermal systems such as drying and incineration can be beneficial and highlights full-scale case studies to quantify the influence in the field.

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