Alternative scenarios for the wastewater and sludge treatment configurations in urban wastewater treatment were studied with the aim of comparing their environmental aspects. As the reference, a conventional activated sludge treatment was chosen including a primary settling and biogas made from the mixed primary and secondary sludge. This reference was then compared to an alternative use of the mixed sludge for the fermentative generation of polyhydroxyalkanoates, PHA and subsequent use of the PHA to substitute polypropylene on the polymer markets. This comparison allows for assessing the environmental priorities between biogas and PHA formation from the carbon content of the sludge. Further, the elimination of the primary settling with the aim of using the carbon content of the wastewater for enhanced nitrogen removal in the activated sludge process was studied. This comparison allows for assessing the environmental priorities between using the carbon for nutrient removal through denitrification and energy production/recovery through biogas or PHA. The preliminary results and conclusions of the study will be presented.
Wastewater sludge, Life Cycle Assessment, PHA, polyhydroxyalkanoates, biogas, nitrogen removal
Main Research Area:
Mixed Culture Polyhydroxyalkanoate Production Workshop II: 'From Waste Organics to Biopolymer to Application', 2008