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Ultraviolet light disinfection is safe, simple, and cost-effective for water resource recovery facilities and has been proven effective for a range of applications and water qualities.

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The Water Environment Federation’s (WEF) Stormwater Institute (SWI) conducted the first national survey of municipal separate storm sewer system (MS4) permittees in 2018 with a follow-up survey in 2020. Like the previous two surveys, the 2022 survey results are statistically significant1 and responses were received from 47 states as well as the District of Columbia and Puerto Rico. The fundamental objectives of these surveys are:

• to identify the information and resource needs of MS4 permittees,

• to better understand MS4 program challenges, and

• to approximate current funding levels and estimated funding needs in the MS4 sector.

In addition, the 2022 survey covers topics such as well-developed, least-developed, and most innovative aspects of stormwater programs. Resilience planning was also included in the survey to capture the incidence of this planning currently and in the future of stormwater programs and the future challenges associated with it.

Approximately 93% of responses in the 2022 survey came from Phase I and Phase II MS4s. Of these responses, approximately 21% were from Phase I communities and 72% from Phase II communities. The remainder of responses came from nontraditional MS4 Phase II permit holders and state departments of transportation (DOTs). Respondents were generally representative of the geographic distribution of MS4s across the United States for both surveys.

The survey was comprised of questions to gather basic information on stormwater programs (size, type of permittee), yes/no-based questions on various aspects of stormwater issues and topics, and several multiple choice questions focusing on stormwater program challenges and needs. Weighted average scores using a 1 through 5 rating system were used in the report to efficiently capture respondent ratings in a single metric.

Responses of 4 or higher reflect strong interest or support for topics. The percentage of responses at this 1Sample of municipal respondents is statistically significant at the 95% confidence interval, with a 5% margin of error.

This fact sheet provides a review of combined heat and power (CHP) technologies for use at water resource recovery facilities (WRRFs). CHP, also called “co-generation,” is defined as the concurrent production of electricity and thermal energy from a power-generating device. Individually, microturbines are on the smaller end of the spectrum of CHP units and, at 92 MW of total installed capacity, they only comprise 0.1% of the total CHP capacity in the United States (U.S. Department of Energy, 2015). Their small size and modular design allow for widespread applicability, and, in terms of number of CHP sites using microturbines as their chosen technology, microturbines comprise approximately 8% of the U.S. CHP market (U.S. Department of Energy, 2016).

Microturbines make use of a Brayton cycle, where air is first drawn into the engine and compressed to high pressure by a radial compressor and is then mixed with fuel in the combustion chamber and continuously ignited. The compressed air is used to drive a turbine that provides torque to both the compressor drawing the air in and an electrical generator. Modern microturbines also make use of a recuperator stage, where hot exhaust air passes by the compressed air entering the combustion chamber, preheating the air before combustion and increasing thermal efficiency.

Microturbines of 30 to 300 kW are an economical option, with the ability to parallel multiple modular units (U.S. Department of Energy, 2016). In December 2019, only 36 sites with a total capacity of 7.4 MW within the U.S. water resource recovery industry were demonstrating this technology and its economic benefits (U.S. Department of Energy, 2019). U.S. installations at WRRFs range in size from 30 kW to 1.6 MW (U.S. Department of Energy, 2019).

Facts about per and polyfluoroalkyl substances (PFAS)

Chemical phosphorus removal helps achieve very low levels of effluent phosphorus, either individually or in combination with biological phosphorus removal. Some typical chemicals used for phosphorus removal include iron and aluminum salts, lime, and earth metals. Most chemicals used for phosphorus removal consume alkalinity and depress pH, except for chemicals such as sodium aluminate or lime, which increase alkalinity and pH. Bench-, pilot-, and field-scale studies have been conducted on various metal salts for the past several decades, providing guidance for the optimization of chemical phosphorus removal processes. This fact sheet includes summaries of key considerations for chemical addition to achieve efficient chemical phosphorus removal.

At the heart of biosolids processing improvements is high performance anaerobic digestion (HPAD). Digestion performance improvements result in more treatment capacity per unit volume to convert wastewater residuals to nutrient-rich, low-odor biosolids, more efficient conversion of organics to methane-rich biogas, and to improve overall biosolids quality. Although there are many conventional high rate mesophilic digestion systems that perform at a high level, there are system modifications to increase performance, which include raising to a thermophilic temperature, decoupling the hydraulic retention time (HRT) and solids retention time (SRT), increasing the solids concentration and pre-treatment processes enhancing hydrolysis, and cyclic metabolic environments.