Harmful Algal Blooms (HAB)

Information for Public Water Systems

harmful algal bloom on a lake

Prepare Now for 2017 Offseason and 2018 Harmful Algal Bloom (HAB) Season

Ohio EPA offered outreach in the form of a webinar on ​October 19, 2017 to Public Water Systems (PWSs) outlining key changes for the 2017-2018 Offseason as well as the 2018 Season. The information was captured in a recorded webinar. 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 (Lesley Jenkins) – (740) 380-5236
Southwest District (Brian Chitti) – (937) 204-1199

Reduced Monitoring Requirements for Ohio Public Water Systems

Initial Seasonal Monitoring Schedule
2018 Off-Season Monitoring Requirements (1/1/18 - 4/30/18)
1, 2 or 3
Off-Season Schedule in Rule
  • Biweekly raw water microcystin; AND
  • Biweekly qPCR screening (paired)
1 or 2
Reduced HAB off-Season Schedule 1/2 A
If any detections of saxitoxins, cylindrospermopsin, sxtA or cyrA genes (6/1/16 - present), then;
  • Biweekly qPCR screening only

Reduced HAB off-Season Schedule 1/2 B
If no detections of saxitoxins, cylindrospermopsin, sxtA or cyrA genes (6/1/16 - present), then;

  • Biweekly raw water microcystins only
  • PWS may elect to be on Schedule 1/2 A with written notification by 12/15/17


3 Reduced HAB Off-Season Schedule 3
  • Monthly qPCR screening; OR
  • Monthly raw water microcystins
  • Only PWSs currently on Schedule 3 are eligible


NOTE: All eligible PWS are being offered reduced monitoring from 10/29/17 – 12/31/17. Any PWS that has had at least two weeks of NO RAW OR FINISHED WATER MICROCYSTINS AND NO MICROCYSTINS GENE (mcyE) DETECTIONS are eligible for biweekly qPCR only. Any mcyE detection will trigger follow-up microcystins sampling within 24 hours of notification. Cyanobacteria screening (qPCR) will continue to be covered by Ohio EPA until 12/31/17 at which time the cost will be the responsibility of the PWS. Ohio EPA’s lab will still be available for microcystins and qPCR testing for a fee.

Any PWS still has the option to follow offseason 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 IDName2018 Offseason Schedule (Jan 1- April 30)2018 Schedule (May 1 - Oct 31)Last Modified
OH7700011AKRON CITY PWS2A210/29/2017
OH7600011ALLIANCE CITY PWS2A210/29/2017
OH0400711AQUA OHIO - ASHTABULA2B210/29/2017
OH4400803AQUA OHIO - LAWRENCE COUNTYSee below**See below**10/29/2017
OH5100414AQUA OHIO - MARION2B210/29/2017
OH7802711AQUA OHIO - MASURYSee below**See below**10/29/2017
OH6835203AQUA OHIO - PREBLESee below**See below**10/29/2017
OH5001611AQUA OHIO - STRUTHERS1A110/29/2017
OH7400614AQUA OHIO - TIFFIN2A210/29/2017
OH4301511AQUA OHIO INC - MENTOR2B210/29/2017
OH2600011ARCHBOLD VILLAGE2B210/29/2017
OH7400011ATTICA VILLAGE2B210/29/2017
OH4700311AVON LAKE CITY PWS2B210/29/2017
OH7700411BARBERTON CITY2A210/29/2017
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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)
*** Columbus Hap Cremean Plant is Schedule 2A, Dublin Road Plant is 2B
All PWS that are eligible for qPCR only sampling will begin the week of Oct. 29, 2017. Please contact your district coordinator if you are unsure. If there are any changes to the 2018 Seasonal schedule, Ohio EPA will contact the Public Water System.

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.