What are cyanobacteria harmful algal blooms (CyanoHABs)? 
Cyanobacteria (previously referred as blue-green algae) are microscopic organisms that live in all types of surface water. They are a form of bacteria that are capable of photosynthesis, like plants. Cyanobacteria tend to multiply rapidly in water that is warm, slow-moving, and rich in nutrients like phosphorus and nitrogen. When this occurs, it is commonly referred to as an “algal bloom.”   
Not all cyanobacterial blooms (algal bloom) will cause illness but can add a very unpleasant taste or odor to water. Other types of cyanobacteria will form toxins that can be extremely dangerous to fish, birds, and mammals, including humans. Blooms from toxin-forming cyanobacteria are commonly referred to as “harmful algal blooms”, or HABs.  
A bloom can appear in several different forms and colors. A “planktonic” bloom is free-floating and is highly recognizable on the surface of the water. Planktonic blooms are capable of existing within a water column, so there can be times when a bloom can “sink”, and a visible surface scum may not be immediately apparent. “Benthic” blooms are cyanobacteria that form mats along sediments and other submerged materials. They are usually dark in color and can break off in pieces.
CyanoHABs can create many difficulties for a drinking water treatment operator. Taste and odor problems, a rapid rise in pH, and increased turbidity are some of the issues an operator will face if a bloom occurs near or upstream of their intake. If toxins are released from the bacteria, a public drinking water system may be faced with a potential health hazard to their customers. Click here to learn more about health advisories specific to cyanotoxins.