Sewage sludge: odour emissions assessment

2. Introduction

One of the main utilisation routes for sewage sludge cake (or biosolids) is recycling to agricultural land as an organic fertiliser and a variety of regulations and codes of practice are in place to ensure it is undertaken safely. However, land applications can be problematic in terms of public perception if sludge recycled to agriculture generates 'excessive' odour emissions during storage on farms (usually in field heaps), and particularly during and after land spreading.

This appraisal and report was commissioned by The James Hutton Institute to help assess the relative intensity of odour emissions which might be generated from three different types of sewage sludge cake during application to land and after spreading. Odour emission rates were measured from disturbed field- stored heaps of sludge cakes produced using the following three treatment systems:

1. Lime treated dewatered cake (LIMED)

2. naerobically digested and dewatered sludge cake (AD)

3. Anaerobically digested and dewatered sludge cake following pre-treatment by a thermal hydrolysis process (THP)