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How to Prevent Algae Blooms in Wastewater Lagoons

December 12th, 2017

For many companies algae blooms in their wastewater lagoons can be dramatic and are a result of excess nutrients from wastewater, fertilizer, and storm water runoff, coinciding with lots of sunlight, warm temperatures and shallow, slow-flowing water. Increasingly these Algae blooms are a public health concern and an ecological problem so it is important that companies firstly select the correct candidate treatment technology upfront to reduce nutrients sufficiently and are proactive and consider adopting an Algae Management Plan downstream to prevent the onset of Algae Blooms.

 

The article below looks at Algae Blooms and lists four common control methods to prevent such blooms from occurring.

 

Algae Blooms Explained

 

An algal bloom is a common term used to describe an increase in the number of algal cells to a point where they can seriously reduce the water quality. Blooms can discolour water, form surface scum, produce unpleasant tastes and odours. Species of blue-green algae may dominate and increase excessively in water when:

  • nutrient levels, particularly phosphorus and nitrogen are sufficient
  • water is still or turbulence is minimal
  • weather pattern is stable for a long time
  • weather is warm (although blooms can occur in cooler weather too)

 

The longer the period of calm weather conditions, the greater the “bloom-forming potential”. Such potential exists mostly in slow flowing rivers or in lakes, dams, weirs and reservoirs.

 

What causes Algae Growth?

The potential for blooms comes from nutrient pollution, an overabundance of the essential plant nutrients nitrogen and phosphorus (possibly caused by a poor performing Sewage Treatment Plant). These elements enter waterways from point sources (such as industrial and wastewater treatment plant discharges), nonpoint sources (such as septic tanks and storm water runoff from urban areas, farms and residential areas), and from nutrient-enriched rainfall. When the concentrations of nitrogen and phosphorus increase in a water body, the right combination of temperature, sunlight and low flow can trigger an algal bloom. Though nitrogen and phosphorus occur naturally and are essential plant nutrients, an overabundance of these nutrients can cause significant imbalances in the water body’s ecology, and blooms are one symptom.

 

Four Common Algae Control Methods

 

  1. Chemicals

Chemical control of algae has been a widespread water quality management practice for over 100 years. Chemical intervention involves treating the water with a variety of additives that precipitate ionized orthophosphates. Using algicides to control algae or cyanobacteria is a long-standing practice for the control of problems caused by these organisms. When used appropriately they can provide immediate short-term and cost-effective control.

 

Benefits: –

  • Wide range of compounds with a history of implementation.
  • Relatively rapid and well-established method.
  • Properties and effects of compounds are typically well-understood.

 

Limitations: –

  • Risk of cell lyses and the release of toxins. Thus, is often used at the early stages of a bloom.
  • Certain algaecides are also toxic to other organisms such as zooplankton, other invertebrates, and fish.

 

 

  1. Aeration

Aerators operate by pumping air through a diffuser near the bottom of the waterbody, resulting in the formation of plumes that rise to the surface and create vertical circulation cells as they propagate outwards from the aerator. This mixing of the water column disrupts the behavior of cyanobacteria to migrate vertically in addition to limiting the accessibility of nutrients.

 

Benefits: –

  • Limits the accessibility of nutrients to the surface.
  • Disrupts the behavior of cyanobacteria to migrate vertically.
  • Reduces competitive advantage of cyanobacteria by maintaining healthy levels of dissolved oxygen.

 

Limitations: –

  • High Opex costs (high costs for maintenance (labor costs) and energy use)
  • Individual devices have limited range; areas further away may remain stratified and provide a suitable environment for growth.
  • Generally more efficient in deeper water columns. Also highly dependent upon the degree of stratification and the air flow rate.

 

 

  1. Mechanical Circulation

Mechanical circulators operate by pumping water from the surface layer downwards or draw water up from the bottom to the surface layer. Similar to aerators, mechanical mixers interfere with stratification of the water column, intercepting conditions ideal for Algae Blooms to occur.

 

Benefits: –

  • Limit the accessibility of nutrients to the surface.
  • Disrupt the behavior of cyanobacteria to migrate vertically.
  • Reduce competitive advantage of cyanobacteria by maintaining healthy levels of dissolved oxygen.

 

 Limitations: –

  • Certain algae prefer an unstable environment and are benefitted by circulation.
  • Individual devices have limited range; areas further away may remain stratified and provide a suitable environment for growth.

 

 

  1. Ultrasound

Controlling algae with ultrasound is a well-established technology that has existed for many years. It is an environmentally-friendly technology that is harmless to fish and plants. An ultrasound device is used to control Algae Blooms by emitting ultrasonic waves of a particular frequency such that the cellular structure of cyanobacteria is destroyed by rupturing internal gas vesicles used for buoyancy control. It is, however, important for the efficiency of the technology that specific frequency programs be used, based on the type of algae that requires controlling.

 

Benefits: –

  • Non-chemical; inexpensive.
  • A single device can cover quite a large area

 

Limitations

  • This technology can be that its associated effectiveness is dependent upon waterbody geometry and cyanobacteria species.

 

 

Next Step

As you can see it takes a lot to manage Algae to ensure blooms are mitigated successfully.

The control methods identified above will hopefully give you a better understanding of how to manage these blooms properly but ultimately selecting the right STP at the start of the process goes a long way to ensuring the plant has the desired nutrient reduction levels to mitigate high nutrient levels in the lagoons which contribute heavily to blooms of this type. For more information on how to select the best candidate technology please refer to our blog article here.

 

MAK Water proudly provides the commercial and industrial sectors with water treatment solutions compliant with local regulations. Our reliable and efficient industrial reverse osmosis systems, water and sewage/wastewater treatment systems have been assisting operations throughout Australia and internationally for over 20 years, as well as in South East Asia and South America.

 

At MAK Water, we’re dedicated to helping industrial operations with their water, wastewater and sewage requirements, via the provision of high performing water treatment plants and systems. We have developed a reputation for delivering superior service and solutions, and for enabling our clients to reduce operating costs and extend equipment operating life.

What water treatment means with MAK Water:

  • System design
  • Project management
  • Custom manufacturing
  • Installation
  • Commissioning
  • System Servicing
  • Remote monitoring
  • Technical support
  • Plant operation
  • Ongoing equipment maintenance and support

 

For smart water treatment, contact MAK Water on 1300 669 032 and to discuss the most appropriate water treatment solution for your business.

Brendan Doherty, MAK Water Operations Manager WA

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