Harmful Algal Blooms (HAB)

Information for Public Water Systems

harmful algal bloom on a lake

Prepare Now for 2018 Harmful Algal Bloom (HAB) Season

A new on-demand HAB update webinar is now available that includes information on monitoring schedules that go into effect on May 1, 2018. View the recording, slides and guidance document for details


Central District (Tya Darden) – (614) 728-3866
Northeast District (Chris Maslo) – (330) 963-1164
Northwest District (Ben Sloan) – (419) 419-3718
Southeast District (Debra Prim) – (740) 380-5421
Southwest District (Brian Chitti) – (937) 204-1199


Reduced Monitoring Requirements for Ohio Public Water Systems


Monitoring Schedule 2018 HAB Season Monitoring Requirements
(5/1/18 - 10/31/18)
1, 2 or 3 Follow Schedule in Rule
  • Weekly raw and finished water microcystins; AND
  • Biweekly qPCR screening (paired with microcystins)
2 Reduced HAB Season Schedule 2
  • Biweekly raw water microcystins; AND
  • Biweekly qPCR screening collected on ALTERNATE week as microcystins sample (not paired)
3 Reduced HAB Season Schedule 3
  • Monthly qPCR screening


NOTE: All eligible PWS are being offered reduced monitoring from 5/1/18 – 10/31/18. 

  • Public water systems located in Ohio EPA’s northwest and southwest district offices should start collecting their qPCR cyanobacteria screening samples the week of May 6, 2018 and continue qPCR sampling on alternating weeks thereafter (for Schedules 1 and 2).
  • Public water systems located in Ohio EPA’s northeast, southeast and central district offices should collect their qPCR cyanobacteria screening samples the week of May 13, 2018 and continue qPCR sampling on alternating weeks thereafter (for Schedules 1 and 2).
  • Schedule 2 systems: Raw water microcystins detections trigger repeat raw and finished water microcystins sampling within 24 hours of notification of results. mcyE gene detections >5GC/uL trigger raw and finished water microcystins sampling within 24 hours of notification of results.  
  • Schedule 3 systems: Any mcyE gene detection will trigger follow-up raw and finished water microcystins sampling within 24 hours of notification of results. 
  • All systems: raw water microcystins detections >5ug/L and finished water microcystins detection trigger additional monitoring requirements (see OAC Rule 3745-90-03).

Any PWS has the option to follow monitoring according to OAC Rule 3745-90-03. More information can be found by viewing the webinar or guidance document located at the top of the page. Please contact your district HAB coordinator with any questions.

PWS IDNameCurrent Monitoring ScheduleLast Modified
OH7700011AKRON CITY PWS25/21/2018
OH7600011ALLIANCE CITY PWS15/21/2018
OH0400711AQUA OHIO - ASHTABULA25/21/2018
OH4400803AQUA OHIO - LAWRENCE COUNTYSee below**5/21/2018
OH5100414AQUA OHIO - MARION25/21/2018
OH7802711AQUA OHIO - MASURYSee below**5/21/2018
OH6835203AQUA OHIO - PREBLESee below**5/21/2018
OH5001611AQUA OHIO - STRUTHERS15/21/2018
OH7400614AQUA OHIO - TIFFIN25/21/2018
OH4301511AQUA OHIO INC - MENTOR25/21/2018
OH2600011ARCHBOLD VILLAGE25/21/2018
OH7400011ATTICA VILLAGE25/21/2018
OH4700311AVON LAKE CITY PWS25/21/2018
OH7700411BARBERTON CITY25/21/2018
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**Wellston South Plant is eligible for Schedule 3.
**Out-of-State purchased water plant, required to collect a minimum of one finished water sample biweekly analyzed for total microcystins beginning the week of Oct. 29, 2017 per (OAC 3745-90-03)

Cyanobacteria (also known as blue-green algae) are microscopic organisms found naturally in surface water that can sometimes multiply to form harmful algal blooms (HABs). HABs can potentially produce toxins capable of causing illness or irritation, sometimes even death, in pets, livestock and humans.

In addition to producing toxins, cyanobacteria can pose other treatment challenges for public water systems, including taste and odor and shortened filter run times. The information below is provided to assist public water system operators with preventing, identifying and responding to HABs.

Prevention and Treatment

HAB Maps and Strategy

Public Water System HAB Response Strategy

Visual Bloom Severity and Toxin Concentrations

Visual bloom severity is often not the best indication of toxin concentrations at intake depths. When the blooms are concentrated at the surface, toxin concentrations at the intake can be lower. For example, when Lake Erie was covered by extensive surface scums (Figure 1) in 2011, toxins were not detected at the Lake Erie public water system intakes. 

When blooms are more dispersed throughout the water column, and not concentrated in surface scums, intake toxin levels can be higher. For example, when the picture in Figure 2 was taken at Maumee Bay State Park in 2011, the cyanobacteria were dispersed throughout the water column, which resulted in a bloom that did not appear severe visually. However, the microcystin concentrations at the public water system intake exceeded 5.0 ug/L. It should be noted that the toxin concentrations at the beach were also high, with microcystin levels exceeding 100 ug/L.  

Lake Erie harmful algal bloom Maumee Bay State Park harmful algal bloom
Figure 1. HAB at Lake Erie with no toxins detected at the intakes (2011). Figure 2. HAB at Maumee Bay State Park with a toxin concentration of greater than 5.0 ug/L at the intake (2011).

Laboratory Information

Responding to a Suspected Bloom

Harsha Lake phytoplankton sample

All public water system owners/operators are encouraged to read through the "Public Water System Harmful Algal Bloom (HAB) Response Strategy" for guidance on responding to HABs.

Anyone Can Report an Algal Bloom

Individuals reporting algal blooms are encouraged to fill out the HAB Report Form and email it, with attached digital photographs if available, to Ohio EPA's HAB Mailbox.

Prevention and Treatment

How to Recognize HABs

Use the following reference documents and photographs to learn more about recognizing HABs. For additional photographs and information, please visit Ohioalgaeinfo.com.

Analyze Samples for Cyanotoxins

Lab Techniques for Detecting Microcystins in Water Using Enzyme-Linked Immunsorbent Assay (ELISA)
This video demonstrates how to measure a particular group of toxins following the Ohio EPA Total Microcystin Analytical Methodology using an ADDA-ELISA kit.


 VIDEO  When in doubt, stay out.

Funding Opportunities for Infrastructure Improvements for HABs

Public Water Systems

Community water systems, publicly or privately owned, that operate surface water treatment systems are eligible for the HAB-discounted interest rate under the Water Supply Revolving Loan Account (WSRLA) program. Eligible projects include treatment system components for HAB treatment, interconnections with other public water systems, elevated storage and development of improved source waters. Nominations for design, and/or construction projects that are directly related to addressing issues from harmful algal blooms (HAB) do not have a deadline and can be submitted to Ohio EPA at any time during the program year. 

For more information, please review the instructions for completing the WSRLA HAB nomination form, available on the Division of Environmental and Financial Assistance webpage.

WPCLF Nutrient Reduction Discount

In response to harmful algal blooms (HABs) and their potential effect on water resources and the raw water supply for drinking water systems, Ohio EPA made $100 million available at a 0% interest rate through the Water Pollution Control Loan Fund (WPCLF) in 2015, 2016 and 2017 for equipment to reduce phosphorus and other nutrients. In 2018, Ohio EPA is offering $50 million at a 0% interest rate for these types of projects. The discounted rate will be available for the portion of the project directly attributed to the nutrient reduction. Standard, below-market interest rate loan funds will be offered for the balance of a proposed project. Ohio EPA will accept nutrient reduction discount (NRD) project nominations for planning, design or construction projects throughout the program year. Applicants who nominated projects for NRD funding in 2017, but did not proceed with projects, and subsequently provided updated schedules during the nomination period to Ohio EPA, will be grandfathered into the 2018 program.

For more information, please review the nutrient reduction guidance and addendum, available on the Division of Environmental and Financial Assistance webpage.

harmful algal bloom on Kelleys Island

To learn more about HABs, check out the list of key references below or visit ohioalgaeinfo.com.


World Health Organization (WHO)

Water Quality Research Australia (WQRA)

U.S. Geological Survey

Water Research Foundation

  • Water Research Foundation home page
  • Algae: Source to Treatment (M57), 2010
  • Removal of Algal Toxins From Drinking Water Using Ozone and GAC, 2002
  • Reservoir Management Strategies for Control and Degradation of Algal Toxins, 2009
  • Early Warning and Management of Surface Water Taste & Odor Events, AwwaRF, 2006
  • Identification of Algae in Water Supplies (CD-ROM), AWWA, 2001

Ohio EPA Introduces New Harmful Algal Bloom Advisory System
A new multi-tiered advisory system to notify the public if microcystin, and other compounds produced by blue-green algae, is detected in treated drinking water at local public water systems throughout the state.