Evaluation of several end-of-pipe measures proposed to control cyanobacteria

While reduction in nutrient loading is a prerequisite for mitigation of harmful cyanobacterial blooms in nutrient-enriched waters, in certain surface waters eutrophication control is not always feasible due to practical and economic constraints or might be effective only in the long run. Yet, the urgent need to control cyanobacteria in water for drinking, irrigation, aquaculture, industry and recreation has spurred the development of a plethora of alternative methods that claim to be fast acting. Here, we provide a critical overview of several of these end-of-pipe measures: effective microorganisms (EM^®), golden algae (Ochromonas), plant/tree extracts, ultrasound and artificial mixing of non-stratifying waters. Most of the end-of the pipe measures claim to provide sustainable control of harmful cyanobacterial blooms, while at best only targeting symptom relief rather than eutrophication relief. Support for “effective” microorganisms, golden algae, plant extracts, ultrasound and artificial mixing of non-stratifying waters to diminish eutrophication problems such that the resulting water quality meets societal and legislation demands is limited, and several proposed underlying mechanisms are doubtful. None of these curative measures seem the desired wide applicable solution to cyanobacterial nuisance; they should not be considered Columbus’s egg. A critical evaluation of end-of pipe measures is crucial for water authorities in their choice for mitigating measures.