Sewage Treatment Facilities (U.S.) — Industry Rollup

North American Industry Classification System (NAICS) 2022 code 22132 — a NAICS industry (5-digit)

Read this first: NAICS 22132 is a single-child pass-through. This 5-digit industry contains exactly one 6-digit national industry — 221320, Sewage Treatment Facilities — and nothing else. At this level the group is, for every practical purpose, identical to that one child. This page gives the level's own definition and ground-truth statistics, then points you to the 221320 primer for the full detail: the investable companies, how the money works, regulation, consolidation, and risks.

1. Overview

This industry collects, treats, and disposes of the wastewater ("sewage") that flows from homes and businesses. It is an essential, recession-resistant service run mostly as a local monopoly — one sewer network per town, no competition for customers.[7] The catch for investors is ownership: about 98% of U.S. wastewater systems are government-owned (cities, counties, and special sewer districts), so the private, for-profit slice that shows up in business statistics is small.[11] There are two practical ways in for an investor: public-market exposure through the handful of regulated water utilities that also run sewage systems — chiefly American Water Works (NYSE: AWK) and Essential Utilities (NYSE: WTRG) — plus water funds and equipment/engineering suppliers; and private exposure through infrastructure funds, contract operators, public-private partnerships, and tax-exempt municipal sewer bonds.[11][12][14] The unifying story is a defensive, capital-hungry business riding a documented $630 billion, 20-year national spending need.[7]

2. What's inside — and why the group equals its one child

NAICS builds industries as a nested tree. At the 5-digit level, 22132 has a single 6-digit member:

Because there is only one child, the 5-digit rollup carries no aggregation — no blending of distinct sub-industries, no mix effects. The scope, the economics, and the numbers are the same as 221320's. The code sits in industry group 2213 (Water, Sewage and Other Systems), inside Sector 22, Utilities.[1] The 5-digit level exists purely as a structural node in the classification; when you analyze 22132, you are analyzing 221320. For the full breakdown of scope and the adjacent codes it excludes (drinking-water systems 221310, septic services 562991, non-sewer waste treatment 562210/56221, and sewer-line construction 237110), see the child primer.[1]

3. Size — this level's ground-truth figures

The statistics below are our ingested federal ground truth for NAICS 22132. Because the 5-digit level equals its one child, they are identical to 221320's, and they measure only the private, for-profit employer slice — the roughly 2% of systems that are investor-owned. Government-owned systems (the other ~98%) sit outside the Census Bureau's business surveys, so these figures materially undercount U.S. wastewater service as a whole.

Concentration of the private slice. The four largest firms earn 54.6% of revenue, the top 8 earn 68%, the top 20 earn 78.9%, and the top 50 earn 87%; the Herfindahl-Hirschman Index (HHI, a standard concentration gauge) is 1,003 — just over the 1,000 line that separates "unconcentrated" from "moderately concentrated."[2] A few investor-owned utilities dominate the for-profit portion.

The real physical scale. For context on how much the business statistics undercount, the EPA's inventory counts 17,544 publicly owned treatment works (POTWs) serving 270.4 million people (82% of the U.S. population), an asset base the American Society of Civil Engineers (ASCE) values at more than $1 trillion and grades "D+".[7][6] Our stats file has no combined municipal-plus-private revenue total for the level — none exists without double-counting — so we do not state one. Treat the physical inventory and the capital-needs numbers as the better gauges of scale.

4. The investable universe

There are essentially no pure public "sewage-treatment" stocks. The closest listed owners are regulated water utilities where wastewater is the smaller, faster-growing leg of a mostly drinking-water business — chiefly American Water Works (NYSE: AWK) and Essential Utilities (NYSE: WTRG); for AWK, wastewater is about $422M, or 9%, of regulated revenue (~330,000 connections, ~170 plants).[11][12] The two have agreed to an all-stock merger that would create a national leader with ~4.7 million connections across 17 states, still pending as of mid-2026.[13] Smaller water utilities (California Water Service, SJW/H2O America, Middlesex Water, American States Water, York Water, and reuse-tilted small-cap Global Water Resources) carry some wastewater but are drinking-water dominated — indirect exposure only.

Value beyond the listed equities sits in three places: thousands of municipal sewer departments and sanitary districts (the bulk of the assets, including giants like New York City's and Chicago's), private contract operators (Veolia, Jacobs, Inframark, together a large share of the outsourced operations market), and infrastructure sponsors rolling those operators up (e.g., New Mountain Capital's 2026 Inframark–Azuria combination, >$2.5B revenue).[9][10][14][15][16] The full company table, market caps, yields, and private-owner detail are in the 221320 primer, Section 4.

5. How the money works

Because the group is one industry, its economics are the child's, and they split by owner type:

• Regulated investor-owned utilities (the public-equity route) earn the classic utility formula — allowed earnings ≈ rate base × approved equity share × allowed return on equity (ROE) — with a state public utility commission (PUC) setting rates. Growth comes from expanding rate base; investor-owned water capital spending has compounded >15% a year, driving ~8–9% rate-base growth.[11][17]
• Municipal systems (the largest owner class) run to break even, recovering costs through sewer charges and funding capital with tax-exempt revenue bonds — a cheap-financing edge private buyers must beat on efficiency.[18]
• Contract operators (asset-light) earn operating and management fees under multi-year operations-and-maintenance (O&M) or design-build-operate (DBO) contracts, not a rate-base return.[25]

There is no merchant wastewater market (no wholesale price, no power purchase agreements), and broad energy tax credits do not apply to treatment itself. See the child primer for the worked rate-case example and the biogas/energy detail.[19][20]

6. Demand drivers

The same forces apply at both levels: regulatory compliance with the Clean Water Act (CWA) is the dominant driver; aging 1970s-era infrastructure ($151.1B of pipe/conveyance needs, $36.5B of combined-sewer-overflow needs); population growth (served population projected to rise from 270.4M in 2022 to 287.4M by 2042); emerging contaminants (PFAS — per- and polyfluoroalkyl substances); climate and stormwater loads; and water reuse and resource recovery.[7][23]

7. Regulation

Two regulators matter, and they map cleanly onto the two owner types. The U.S. Environmental Protection Agency (EPA) and delegated state agencies are the cost regulators, administering CWA discharge permits (the National Pollutant Discharge Elimination System, or NPDES), secondary-treatment standards, and Part 503 biosolids rules. State PUCs are the economic regulators of investor-owned utilities only; municipal systems set rates through local boards. The live wildcard is PFAS — the EPA had not finalized discharge or biosolids limits as of early 2026, and outcomes could impose large unfunded costs. FERC and the NRC do not regulate wastewater. Full detail is in the child primer.[22][23][24]

8. Consolidation

Sewage treatment is a natural local monopoly and highly fragmented — 17,544 POTWs, most of them small systems short on capital and engineering depth.[7] That fragmentation drives consolidation on three tracks: regulated roll-ups (utilities buying small municipal/private systems for a regulated return, aided by "fair-market-value" laws in about a dozen states); the landmark American Water × Essential Utilities merger (announced October 2025, targeting a Q1 2027 close); and contract-operator roll-ups plus public-public regionalization.[11][13][16]

9. Risks

The level's risks are the child's: affordability and rate politics; regulatory lag (earned ROE below allowed ROE); acquisition-premium risk (goodwill that earns no return); PFAS/biosolids liability; interest-rate sensitivity in a debt-heavy business; construction inflation; wet-weather and drought volume swings; cyberattack on plant control systems; an aging operator workforce; and approval/timing risk on the pending AWK–WTRG merger.[11][13][23][10]

10. How to invest & outlook

The attractive, defensive part of the group is regulated ownership — AWK and WTRG (converging via merger), water ETFs (Invesco Water Resources, PHO; First Trust Water, FIW) for diversified baskets, and picks-and-shovels equipment/engineering suppliers selling into the $345.7 billion wastewater capital program; the profile is a low-beta, dividend-growth compounder priced at a premium (AWK ~24× earnings, ~2.6% yield; WTRG ~18×, ~3.5% yield).[7][23][24][25] Private investors buy small regulated systems, run O&M/DBO platforms, do collection-system rehabilitation, or hold tax-exempt municipal sewer revenue bonds — the most accessible fixed-income exposure.[11][14][18]

A documented $630 billion, 20-year need and a "D+" grade guarantee decades of mandated spending, only partly closed by federal programs (the Clean Water State Revolving Fund, ~$194B since inception; the Water Infrastructure Finance and Innovation Act, or WIFIA, ~$22B).[6][7][26] Expect steady above-inflation capital investment, accelerating consolidation, and rate-base compounding, with PFAS regulation the single biggest swing factor. Because 22132 is one industry, that outlook is the 221320 outlook — read the child primer for the complete picture.

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Sources

1. U.S. Census Bureau, "NAICS 221320 — Sewage Treatment Facilities" profile and cross-references (NAICS 2022 definition, hierarchy, and exclusions). https://data.census.gov/profile/221320_-_Sewage_Treatment_Facilities?codeset=naics~221320
2. U.S. Census Bureau, 2022 Economic Census (NAICS 221320; receipts $2.420B, 401 firms; concentration ratios CR4 54.6% / CR8 68% / CR20 78.9% / CR50 87%; HHI 1,003.4). [Core figures per Histometrics ingested federal statistics for NAICS 22132.] https://data.census.gov/table/ECNBASIC2022.EC2222BASIC
3. U.S. Census Bureau, County Business Patterns 2023 (NAICS 221320; 538 establishments, 6,989 employees, $511.8M annual payroll, $130.7M Q1 payroll). [Core figures per Histometrics ingested federal statistics for NAICS 22132.] https://www.census.gov/programs-surveys/cbp.html
4. U.S. Small Business Administration, Table of Small Business Size Standards, effective March 17, 2023 (NAICS 221320 = $35.0M receipts); ASCE, 2025 Infrastructure Report Card: Wastewater (grade D+, systems valued >$1T). https://www.sba.gov/document/support-table-size-standards; https://infrastructurereportcard.org/cat-item/wastewater-infrastructure/
5. U.S. EPA, 2022 Clean Watersheds Needs Survey (CWNS) Report to Congress, 2024 (17,544 POTWs serving 270.4M / 82%; $630.1B total, $345.7B wastewater subtotal and categories; 287.4M served projected by 2042). https://www.epa.gov/system/files/documents/2024-05/2022-cwns-report-to-congress.pdf
6. New York City Department of Environmental Protection, "Wastewater Treatment Plants" (14 plants, ~1.3 billion gallons/day). https://www.nyc.gov/site/dep/water/wastewater-treatment-plants.page
7. Metropolitan Water Reclamation District of Greater Chicago, "Wastewater Treatment." https://mwrd.org/what-we-do/protecting-water-quality/wastewater-treatment
8. American Water Works Company, 2025 Form 10-K, filed 2026 (~98% of U.S. wastewater systems government-owned; wastewater $422M / 9% of regulated revenue, ~330,000 connections, ~170 plants; fair-market-value laws). https://www.sec.gov/Archives/edgar/data/1410636/000141063626000034/awk-20251231.htm
9. Essential Utilities, Full-Year 2025 Results, February 2026 (~5.5M people, 9 states; municipal wastewater acquisitions). https://www.essential.co/news-releases/news-release-details/essential-utilities-reports-financial-results-full-year-2025
10. American Water & Essential Utilities, merger announcement, October 2025, and 2026 state-approval updates (0.305 exchange ratio; 4.7M connections / 17 states; ~$29.3B rate base; Q1 2027 target). https://ir.amwater.com/news-and-events/financial-releases/financial-release-details/2025/American-Water-and-Essential-Utilities-to-Merge-as-a-Leading-Regulated-U-S--Water-and-Wastewater-Utility/default.aspx
11. Veolia North America, "Public Water and Wastewater Systems" (550+ communities; largest private operator). https://www.veolianorthamerica.com/what-we-do/water-capabilities/public-water-wastewater-systems
12. Bluefield Research, U.S. Municipal Water and Wastewater Utility Outsourcing Market (Veolia / Jacobs / Inframark ~81% of outsourced O&M capacity). https://www.bluefieldresearch.com/download/36547
13. New Mountain Capital, "Combination of Azuria Water Solutions and Inframark," April 2026 (combined business >$2.5B revenue). https://www.businesswire.com/news/home/20260423137649/en/New-Mountain-Capital-Completes-Combination-of-Azuria-Water-Solutions-and-Inframark
14. National Association of Regulatory Utility Commissioners, Ratemaking Fundamentals and Principles (rate-base / allowed-return model). https://www.naruc.org/commissioners-desk-reference-manual/3-ratemaking-fundamentals-and-principles/
15. U.S. EPA, Water Affordability Resources for Utilities and Wastewater Utility User Charge guidance (municipal cost recovery, user fees, tax-exempt/subsidized debt). https://www.epa.gov/waterfinancecenter/water-affordability-resources-utilities
16. U.S. EPA, Energy Efficiency for Water Utilities (water/wastewater ~2% of U.S. energy; 30–40% of municipal energy bills). https://www.epa.gov/sustainable-water-infrastructure/energy-efficiency-water-utilities
17. Internal Revenue Service, Clean Electricity Investment Credit (§48E) and Elective Pay and Transferability overview. https://www.irs.gov/credits-deductions/clean-electricity-investment-credit
18. U.S. EPA, Municipal Wastewater and NPDES, Secondary Treatment Standards, National Pretreatment Program, and Part 503 biosolids rules. https://www.epa.gov/npdes/municipal-wastewater
19. U.S. EPA, Draft Sewage Sludge Risk Assessment for PFOA and PFOS (2025) and POTW Influent PFAS Study (2026). https://www.epa.gov/biosolids/draft-sewage-sludge-risk-assessment-perfluorooctanoic-acid-pfoa-and-perfluorooctane
20. Federal Energy Regulatory Commission, jurisdiction explainer (wholesale power, not sewer rates). https://www.ferc.gov/explainer-transmission-planning-and-cost-allocation-final-rule
21. U.S. EPA, Decision-Makers' Guide to Alternative Service Delivery Options (O&M, DBO, concessions). https://www.epa.gov/financial/decision-makers-guide-alternative-service-delivery-options-public-utility-projects
22. CISA, EPA and FBI, Top Cyber Actions for Securing Water Systems, February 2024. https://www.cisa.gov/news-events/alerts/2024/02/21/cisa-epa-and-fbi-release-top-cyber-actions-securing-water-systems
23. American Water Works Company, Dividend Increase release, April 2026, and Macrotrends AWK price/P/E history; S&P Global Market Intelligence water-utility capex analysis (~2.6% yield; P/E ~24; rate-base growth ~8–9%). https://www.macrotrends.net/stocks/charts/AWK/american-water-works/stock-price-history
24. Essential Utilities historic stock lookup and ChartExchange WTRG data (~3.5% yield; P/E ~18). https://www.essential.co/stock-information/historic-lookup
25. Invesco Water Resources ETF (PHO) and First Trust Water ETF (FIW). https://www.invesco.com/us/en/financial-products/etfs/invesco-water-resources-etf.html
26. U.S. EPA, Clean Water State Revolving Fund (~$194B since inception) and WIFIA loan announcements (~$22B). https://www.epa.gov/cwsrf/about-cwsrf