Harmful Algal Blooms (HAB)

Information for Public Water Systems

 As a precautionary response to COVID-19, Ohio EPA is currently operating with most staff working remotely. If you are working with our staff on a current project and you know the name of the employee you are working with, email them at firstname.lastname@epa.ohio.gov or call them directly. The Agency website has contact information for every district, division, and office. In order to reach us, please contact Ohio EPA’s main phone line at (614) 644-3020 or the main line for the division or office you are trying to reach.

After March 23, our district offices and Central Office will be temporarily closed and will have increasingly limited ability to receive deliveries, plans, etc. All entities are encouraged to submit plans, permit applications, etc., electronically where there are existing avenues to do so, such as the eBusiness Center (eBiz). Please refer to the list of available services on the main eBiz webpage. We encourage you to make use of all that apply, even if you have not used eBiz in the past. Plans under 25 MB can be emailed. For large plans over 25 MB, entities should work with the reviewer/division to upload via LiquidFiles. Directions for submitting docs via LiquidFiles is available on YouTube. We apologize for the inconvenience and thank you in advance for your understanding. If you wish to send hard copies of documents to any of Ohio EPA’s district offices, the best method to ensure we receive these documents is to send them via U.S. Mail. Since all offices are closed, deliveries outside of U.S. Mail (FedEx, UPS) will likely be returned because the offices are closed and deliveries cannot be made.

To report a spill or environmental emergency, contact the spill hotline (800) 282-9378 or (614) 224-0946

harmful algal bloom on a lake

Harmful Algal Bloom (HAB) Monitoring

Public water systems with a surface water source(s) must comply with HAB monitoring and reporting rule requirements (OAC 3745-90-03). Public water systems may be eligible for reduced monitoring, based on cyanotoxin occurrence and treatment capability. Please click the links, below, to view the HAB monitoring schedule assignments for each public water system, HAB monitoring requirements by schedule , and HAB sampling triggers and implementation guidance.


Additional information is provided in the 2020 HAB Season Webinar and 2020 PWS Response Strategy.


Schedule 1 and 2: If your PWS has elected to sample qPCR, PWSs will collect their first biweekly qPCR sample the week of November 1, 2020. If you have not elected to sample for qPCR, you will collect your first biweekly raw water microcystins sample the week of November 8, 2020. Cyanobacteria screening or raw water microcystins samples must be collected on alternating weeks thereafter.

Schedule 3: PWSs must collect a monthly qPCR sample beginning November 1, 2020.

Schedule 4: PWSs must collect a biweekly finished water microcystins sample beginning November 8, 2020.

If you are a system that does not qualify for reduced monitoring, please continue weekly monitoring for microcystins at both raw and finished sampling points.

Schedule 1 and Schedule 2 PWS:

Biweekly qPCR Monitoring
1 Sample Required Between
Biweekly Microcystins Monitoring
1 Sample Required Between
11/1/2020 and 11/7/2020 11/8/2020 and 11/14/2020
11/15/2020 and 11/21/2020 11/22/2020 and 11/28/2020
11/29/2020 and 12/5/2020 12/6/2020 and 12/12/2020
12/13/2020 and 12/19/2020 12/20/2020 and 12/26/2020
12/27/2020 and 1/2/2021 11/3/2021 and 1/9/2021
1/10/2021 and 1/16/2021 1/17/2021 and 1/23/2021
1/24/2021 and 1/30/2021 1/31/2021 and 2/6/2021
2/7/2021 and 2/13/2021 2/14/2021 and 2/20/2021
2/21/2021 and 2/27/2021 2/28/2021 and 3/6/2021
3/7/2021 and 3/13/2021 3/14/2021 and 3/20/2021
3/21/2021 and 3/27/2021 3/28/2021 and 4/3/2021
4/4/2021 and 4/10/2021 4/11/2021 and 4/17/2021
4/18/2021 and 4/24/2021 4/25/2021 and 5/1/2021

Please contact your district HAB coordinator with any questions. To find your district office, please visit https://epa.ohio.gov/Contact.


Section Manager (Colin White) – (614) 644-2759
Section Supervisor (Emilie Eskridge) – (614) 644-2765
State HAB Specialist (Ruth Briland) – (614) 369-4045
HAB Compliance (Marissa Ganzfried) – (614) 644-3140
Central District (Bridgette Marchio) – (614) 728-3870
Northeast District (Chris Maslo) – (330) 963-1164
Northwest District (Ben Sloan) – (419) 419-3718
Southeast District (Jessica Dingman) – (740) 380-5236
Southwest District (Brian Chitti) – (937) 204-1199

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

If you see surface scum or something that looks like cyanobacteria at Ohio’s rivers, lakes, or public swimming beaches, report it to Ohio EPA by completing the online bloom report form or the paper form and emailing it to HABmailbox@epa.ohio.gov.

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 Research Australia (WaterRA)

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
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