Striking the Balance between Nutrient Removal, Greenhouse Gas Emissions, Receiving Water Quality, and Costs

Abstract

This Water Environment Research Foundation study considered the relationship between varying nutrient-removal levels at wastewater treatment plants, greenhouse gas emissions, receiving water quality (measured by potential algal production), and costs. The effluent nutrient concentrations required by some U.S. permits are very low, approaching the technology-best-achievable performance. This study evaluated five different treatment levels at a nominal 40 ML/d (10 mgd) flow. Greenhouse gas emissions and costs increase gradually up to the technologies' best-achievable performance, after which they increase exponentially. The gradual increase is attributed to additional biological treatment facilities, increased energy and chemical use, and additional tertiary nitrogen and phosphorus removal processes. Within the limited focus of this study, the evaluation shows that a point of diminishing return is reached as nutrient-removal objectives approach the technology-best-achievable performance, where greenhouse gas emissions and cost of treatment increases rapidly while the potential for algal growth reduce marginally.

A Review of Phosphorus Removal Technologies and Their Applicability to Small-Scale Domestic Wastewater Treatment Systems

“…Very little, up to date economic information exists for many technologies described in this review. Most studies to date have considered economic advantages and disadvantages in relation to optimizing specific systems and none focus specifically on small-scale application (e.g., Jiang et al, 2005;Falk et al, 2013). Jiang et al (2005) found that dosing alum to a conventional activated sludge plant was the most cost-effective solution unless final effluent P concentrations of <0.13 mg/L are required.…”

Characterization of the dissolved phosphorus uptake kinetics for the effluents from advanced nutrient removal processes

“…From previous studies, it is suggested that removing the more refractory fraction remaining in the final effluents would require aggressive tertiary treatment, which would increase operational costs and secondary environmental impacts (Falk et al, 2013). The modification proposed in our study could reduce the additional energy and chemical usage, and sludge disposal relative to the minor absolute P removal at low effluent TP concentrations.…”

Linking Hydrobiogeochemical Processes and Management Techniques to Close Nutrient Loops in an Arid River

“…A small number of samples (n = 3) were impacted by local synthetic fertilizers with at least 60% of their nitrate from that source. Modern wastewater treatment facilities are designed to utilize tertiary (to reduce nutrient loads and disinfect) and quaternary treatment procedures (to remove pharmaceuticals and personal care products) (Sonune and Ghate, 2004;Carey and Migliaccio, 2009;Falk et al, 2013). Given that wastewater is the dominant source of nutrients to the Middle Rio Grande, some modifications could be employed to close nutrient loops and maximize recycling of this limited resource.…”

“…Given that wastewater is the dominant source of nutrients to the Middle Rio Grande, some modifications could be employed to close nutrient loops and maximize recycling of this limited resource. For example, while withinwastewater treatment plant nutrient removal is typically deemed essential to prevent eutrophication of downstream aquatic environments in many areas, in aridlands, where wastewater-rich river water is diverted for agricultural irrigation, these nutrient removal steps may be energetically expensive (Falk et al, 2013) and deplete valuable nutrient sources for crops. Accordingly, reducing the level of treatment to secondary treatment or excluding nutrient removal steps in tertiary treatment prior to delivery to the agricultural system would provide an opportunity to conserve both energy and nutrient resources.…”