WERF Nutrient Challenge – Nutrient Regulations, Treatment Performance, and Sustainability Collide

Abstract

The WERF Nutrient Challenge has developed a series of projects to provide information regarding evolving numeric nutrient criteria, how reliable existing technologies perform to meet treatment objectives, the sustainability impacts of nutrient removal at meeting various treatment levels, and other factors. This paper provides a national perspective on the approaches taken by states and other agencies to set in-stream nutrient criteria and the approach to set discharge limits for treatment plants. The approaches range from implementing EPA's ecoregion criteria to TMDL based load allocations. In some cases an adaptive management approach is used. While these approaches vary nation wide, their implications is often to move to very low nutrient concentrations.A study of 22 full scale wastewater treatment plants forms the basis for assessing the reliability and variability of nutrient removal plants achieving stringent limits. The results using technology performance statistics show that the averaging period for meeting discharge limits plays a key role in the ability of a plant to meet permit. The performance statistics also indicate the ideal performance that can be expected. Combining this information with nutrient speciation studies, the best achievable performance for nutrient removal can be identified for a specific technology.Additional facilities and resources are needed to meet increasingly stringent nutrient discharge requirements. The sustainability impacts of the additional treatment is presented in terms of the greenhouse gas (GHG) emissions from operation of the facilities, as required for discharge limits ranging from secondary treatment to limits below conventional treatment capability (requiring reverse osmosis). The evaluation of benefits associated with reduced algal growth potential and increasing GHG emissions, shows that the cost benefit ratio change significantly when the nutrient limits are reduced below < 3 mg N /L total nitrogen and < 0.1 mg P/L total phosphorus. Alternative nutrient management and control strategies could be considered for these lower limits.

Life-Cycle Assessment of Advanced Nutrient Removal Technologies for Wastewater Treatment

“…Comparison Here, we report global-warming results of 0.6−0.9 kg CO 2 eq/ m 3 , compared to 0.4−0.5 kg CO 2 eq/m 3 for Level 1 equivalent plants from Falk et al and 0.4−0.6 kg CO 2 eq/m 3 for Foley et al (Figure 3). 5,9,51 Disparity in these results can be attributed to differences in scope, process simulation tools, and emission factors.…”

“…In addition, the enhanced tertiary chemical phosphorus removal process is required to deliver the lower Level 2 Phosphorus concentration. ,− Level 3 is known as the best achievable performance level and targets extremely low effluent nutrient levels to comply with ongoing or anticipated regulations. A WERF-sponsored survey and independent studies on advanced phosphorus removal technologies ,, have indicated that, to attain these extremely low level of nutrient levels, multiple tertiary processes for chemical P removal are necessary, and the addition of more external carbon for postdenitrification is required. ,, WWTPs performance at this level of treatment are also dependent on local weather conditions, process implementation, and wastewater characteristics as well as skilled operation and maintenance…”

“…Although technology-based limits have specific guidelines, water-quality-based limits may vary widely depending on location, leading to very strict nutrient limits for some sites . USEPA-recommended ecoregional criteria provide a starting point for states to identify precise the nutrient levels needed to protect aquatic life and maintain recreational or other uses on a site-specific or regional basis. − …”

“…A WERF-sponsored survey and independent studies on advanced phosphorus removal technologies 6,31,33 have indicated that, to attain these extremely low level of nutrient levels, multiple tertiary processes for chemical P removal are necessary, and the addition of more external carbon for postdenitrification is required. 3,26,28 WWTPs performance at this level of treatment are also dependent on local weather conditions, process implementation, and wastewater characteristics as well as skilled operation and maintenance. 6 Treatment Plant Process Configuration Design Alternatives.…”

Identification of Key Basic Parameters Involved in Carbon Emissions in Full-Scale Wastewater Treatment Plants

“…By evaluating the carbon emissions of 50 WWTPs in Shanghai, Jiarui, Xi et al pointed out that the lowest carbon emission was obtained when influent COD Cr was 150~250 mg/L and NH 3 -N was 15~25 mg/L [14]. In contrast, stricter discharge limits led to a higher emission intensity [15]. Highly influent nutrients consume more oxygen and chemical agents, while poorly influent nutrients need extra carbon sources to support the growth of microorganisms, which can remove nitrogen.…”