'Doing the Two-Step' – Reduced Energy Consumption Sparks Renewed Interest in Multistage Biological Treatment

摘要

Historically, the implementation of two-stage treatment (i.e. carbonaceous removal followed bynitrification) has been implemented at wastewater treatment plants that originally were designedwith the carbonaceous removal step first. Some of the primary reasons for implementing twostagetreatment included ease of implementation (i.e. challenging to de-rate existing plants toallow for nitrification) and to reduce or mitigate the impact of toxic substances on the nitrifyingorganisms. Another key benefit of two-stage treatment that is gaining greater prominence inrecent years is the improved overall sustainability of these processes compared to single stagetreatment in terms of aeration energy and biogas production. This paper examines, through ageneralized modeling study, the difference in aeration energy and biogas production of singlestage activated sludge compared to two-stage treatment processes (i.e. conventional two-stagetreatment and the A/B Process). The results from this study suggest that overall aeration energysavings could be in the order of 15-20% less with two stage treatment processes, while biogasproduction could be 25-38% higher with two-stage treatment. These two factors are the primaryreasons why some treatment facilities (e.g. Strass, Austria) are demonstrating that net energypositive wastewater treatment is indeed possible.