Economic Evaluation of Alternatives for Sidestream Nutrient Removal and Recovery

Sidestream nitrogen and phosphorus loads from wastewater treatment plants that perform nutrient removal and have anaerobic digestion can account for 15-20 percent of influent nitrogen, and 20-30 percent of influent phosphorus. Due to the negative impact that nutrient peaks can have on the mainstream process, sidestream treatment is often an economical option for managing these recycle nutrient loads. This paper presents information from economic evaluations of different sidestream nutrient treatment technologies at various utilities. Results from these evaluations indicate that implementing sidestream treatment can defer larger capital investments needed to meet stringent nutrient limits. Further, our evaluations indicated that nitritation/deammonification is the lowest cost alternative among biological nitrogen removal alternatives for sidestream treatment. When consider phosphorus treatment, our findings demonstrate that there is significant variation in the business models and costs associated with phosphorous recovery (via struvite precipitation) processes being marketed today. Although it is expected that these business models will converge over time, this work clearly indicates that utilities need to perform a systematic evaluation of all potential options under local specific conditions to determine the most cost effective strategy for sidestream nutrient treatment.