Online monitoring of volatile organic compound production and emission during sewage sludge composting.

The production and emission of volatile organic compounds (VOCs) were studied using an online monitoring method in a well-operated sludge composting plant. Results indicated that VOC production within the pile was different from emission at the pile surface. The total mass of VOC production was 1.09gCkgDM(-1), which was 2.3 times as high as the total mass of emission. The maximum production and emission masses occurred in the mesophilic phase of composting and were 444 and 202mgkgDM(-1)d(-1), respectively. VOC production and emission rates also varied rapidly at different times. The relationship of VOC production rates and time in an on/off aeration cycle at different periods could be expressed as a quadratic equation, while the emission rate could be expressed as a linear equation.