Designing an observing system for early detection of harmful algal blooms.

Abstract

Harmful algal blooms (HABs) are a serious and growing threat to many desalination plants. It is therefore important to limit the impact from HABs by preventing blooms from reaching seawater reverse osmosis (SWRO) plants in the first place, while also mitigating their effects through pretreatment and other actions within the plant once intake has occurred. In this chapter, traditional and emerging technologies in the field of HAB detection and monitoring are summarized. Also advice on designing “observing systems” for early detection or characterization of algal blooms is provided. These systems will vary dramatically in terms of the number of parameters to be measured, the number of stations, frequency of sampling and instruments used - all determined by desalination plant budgets and personnel skills, the nature of the HAB threat for a given plant or region, and other such considerations. An observing system might be as simple as visual observations of the color or nature of the intake water, or as complex as a moored array of autonomous sensors outside the plant, or weekly surveys from small vessels to determine what algal species and blooms are in the intake area or surrounding waters, and thus likely to impact the plant. There are a number of factors that complicate the design of an observing system. One is the diversity of HAB species. Potentially harmful phytoplankton are found in many groups (mainly eukaryotes) such as dinoflagellates, raphidophytes, diatoms, euglenophytes, cryptophytes, haptophytes, pelagophytes, and chlorophytes (see Chapter 1), but prokaryotes, (cyanobacteria) are also a concern. While dinoflagellates comprise the majority of toxic HAB species in the marine environment where desalination plants are located, many of the toxic species that pose a threat to drinking water supply in fresh- or brackish-water systems are cyanobacteria. A second factor is that phytoplankton distribution in the sea is not uniform vertically or horizontally in space or in time. This is termed “patchiness” and results from the interaction between physical and biological processes. Examples are presented later in this chapter. The In this chapter, traditional and emerging technologies in the field of HAB detection and monitoring are summarized. Also advice on designing “observing systems” for early detection or characterization of algal blooms is provided. These systems will vary dramatically in terms of the number of parameters to be measured, the number of stations, frequency of sampling and instruments used - all determined by desalination plant budgets and personnel skills, the nature of the HAB threat for a given plant or region, and other such considerations. An observing system might be as simple as visual observations of the color or nature of the intake water, or as complex as a moored array of autonomous sensors outside the plant, or weekly surveys from small vessels to determine what algal species and blooms are in the intake area or surrounding waters, and thus likely to impact the plant. There are a number of factors that complicate the design of an observing system. One is the diversity of HAB species. Potentially harmful phytoplankton are found in many groups (mainly eukaryotes) such as dinoflagellates, raphidophytes, diatoms, euglenophytes, cryptophytes, haptophytes, pelagophytes, and chlorophytes (see Chapter 1), but prokaryotes, (cyanobacteria) are also a concern. While dinoflagellates comprise the majority of toxic HAB species in the marine environment where desalination plants are located, many of the toxic species that pose a threat to drinking water supply in fresh- or brackish-water systems are cyanobacteria. A second factor is that phytoplankton distribution in the sea is not uniform vertically or horizontally in space or in time. This is termed “patchiness” and results from the interaction between physical and biological processes. Examples are presented later in this chapter. TheIn this chapter, traditional and emerging technologies in the field of HAB detection and monitoring are summarized. Also advice on designing “observing systems” for early detection or characterization of algal blooms is provided. These systems will vary dramatically in terms of the number of parameters to be measured, the number of stations, frequency of sampling and instruments used - all determined by desalination plant budgets and personnel skills, the nature of the HAB threat for a given plant or region, and other such considerations. An observing system might be as simple as visual observations of the color or nature of the intake water, or as complex as a moored array of autonomous sensors outside the plant, or weekly surveys from small vessels to determine what algal species and blooms are in the intake area or surrounding waters, and thus likely to impact the plant. There are a number of factors that complicate the design of an observing system. One is the diversity of HAB species. Potentially harmful phytoplankton are found in many groups (mainly eukaryotes) such as dinoflagellates, raphidophytes, diatoms, euglenophytes, cryptophytes, haptophytes, pelagophytes, and chlorophytes (see Chapter 1), but prokaryotes, (cyanobacteria) are also a concern. While dinoflagellates comprise the majority of toxic HAB species in the marine environment where desalination plants are located, many of the toxic species that pose a threat to drinking water supply in fresh- or brackish-water systems are cyanobacteria. A second factor is that phytoplankton distribution in the sea is not uniform vertically or horizontally in space or in time. This is termed “patchiness” and results from the interaction between physical and biological processes. Examples are presented later in this chapter. The In this chapter, traditional and emerging technologies in the field of HAB detection and monitoring are summarized. Also advice on designing “observing systems” for early detection or characterization of algal blooms is provided. These systems will vary dramatically in terms of the number of parameters to be measured, the number of stations, frequency of sampling and instruments used - all determined by desalination plant budgets and personnel skills, the nature of the HAB threat for a given plant or region, and other such considerations. An observing system might be as simple as visual observations of the color or nature of the intake water, or as complex as a moored array of autonomous sensors outside the plant, or weekly surveys from small vessels to determine what algal species and blooms are in the intake area or surrounding waters, and thus likely to impact the plant. There are a number of factors that complicate the design of an observing system. One is the diversity of HAB species. Potentially harmful phytoplankton are found in many groups (mainly eukaryotes) such as dinoflagellates, raphidophytes, diatoms, euglenophytes, cryptophytes, haptophytes, pelagophytes, and chlorophytes (see Chapter 1), but prokaryotes, (cyanobacteria) are also a concern. While dinoflagellates comprise the majority of toxic HAB species in the marine environment where desalination plants are located, many of the toxic species that pose a threat to drinking water supply in fresh- or brackish-water systems are cyanobacteria. A second factor is that phytoplankton distribution in the sea is not uniform vertically or horizontally in space or in time. This is termed “patchiness” and results from the interaction between physical and biological processes. Examples are presented later in this chapter. The simultaneous use of multiple monitoring methods is therefore often necessary to characterize the species composition and extent of blooms, but even then, a full picture of the distribution of a HAB may not be achievable.