Aquatic Pest Management for Power Stations

The electricity power plant manager

is confronted with the growth of aquatic biomass which impacts the performance of the power plant.

Problems are experienced with the growth of the following pests:

  • Aquatic fauna (mussels, barnacles, invertebrates, fish, etc.)
  • Aquatic vegetation (pondweeds and others)
  • Algae
  • Fungi
  • Bacteria

Conditions in a typical electric power plant cooling water system are close to the ideal medium for biological growth referred to as biofouling. Power plant cooling water systems provide the ideal condition (water temperature = 32-38 oC and pH8-9) for the biological growth of aquatic organisms as it provides nutrients, heat, air and sunlight.

Aquatic vegetation such as pondweeds (Potamogeton sp.) and algae (Cladophora, Oedogonium, etc.) proliferate in the holding/storage dams of power stations, reducing the capacity of these dams and blocking off take pumps.  Aquatic vegetation can block the cooling systems of pumps and cause it to malfunction, disrupting continuous water delivery.

Algae require sunlight to grow and use chlorophyll to convert carbon dioxide (CO2) to biomass.  Algal biomass is found on the wet exposed surfaces such as the distribution decks, structural members, plenum and drift eliminator.  Fragments of algae may also interfere with water distribution and cause plugging in heat exchangers.

Fungi are simple organisms containing no chlorophyll but have the ability to cause serious problems in cooling towers.  Fungi (yeasts) foul heat exchanger surfaces and molds are responsible for wood rot in cooling tower structures.

Bacteria flourish throughout the power station cooling system, including the heat exchanger surfaces and cooling tower itself.  These bacteria produces slime layers which forms, with other deposits, a biofilm (process is called biofouling) on surfaces of the heat exchangers and the cooling tower.  Bacteria also causes, under anaerobic (no oxygen) conditions, corrosion called microbial induced corrosion or in short MIC.  Sulphate reducing bacteria (SRB’s) reduces sulphates to hydrogen sulphide (H2S) which corrodes metal surfaces.  Acid producing bacteria (APB’s) produces organic acids which also induces corrosion in power plant structures.  Biofouling often serves as the “glue” that binds other deposits to the heat transfer surfaces.

Legionella are bacterial pathogens which pose potential health risks when proliferating in cooling towers and condensers.  When Legionella pneumophila bacteria are expelled from cooling towers as an aerosol in the drift there is the potential that people in a radius of 6-7 km from the power plant may be infected with the pathogen which could lead to either Legionnaires’ Disease or the less serious Pontiac fever.

Biofouling control

Once growth of aquatic organisms is established to a degree that it reduces the cooling efficiency, chemical treatment is not very effective to remove the organic biomass; the only solution is then to mechanically clean the system. For effective biofouling control, the object is to control the waterborne organisms before they have a chance to attach themselves to the internals of the cooling system and block the water flow, reducing cooling efficiency.

ENVIROKONSULT™ can assist the power plant manager by implementing a preventative maintenance aquatic pest management programme on the water system of the power plant to control all organisms before the magnitude of the infestation reach a point where cooling efficiency is impaired.

ENVIROKONSULT™’s services to the POWER INDUSTRY include the following:

  • Aquatic pest management in power station cooling systems.  Aquatic vegetation, algae, mussels and barnacles are effectively controlled with organic pesticides without any corrosion of equipment.
  • Aquatic vegetation and algae control in environmental dams.  Environmental or primary dams are very vulnerable to infestation by algae and aquatic vegetation.  This nuisance biomass can be managed effectively by our team by the implementation of a scientifically designed control programme.
  • Aquatic vegetation, algae and invertebrate control at the primary intake structures.
  • Aquatic vegetation, algae control and invertebrate control in the cold water ponds.
  • Aquatic vegetation, algae control and invertebrate control in the outlet structures of power stations.
  • Implement a water quality monitoring programme to evaluate the water quality of the system and test for the presence of Legionella bacteria.