Bioengineering

Bioaugmentation

Bacterial Products

Produits Biologiques

Beneficial Reuse

Table of Contents

New Training CD's

New Training Manuals

Benchmarks

Industry

FYI

Consulting

Training

Additional links

Miscellaneous

Audits

Troubleshooting Tips

Microscopic Analyses

Case Histories

Additional Troubleshooting Topics

Duckweed

Algae

Lift Stations

Wastewater Microbiology

Microscopic Analyses

Photomicrographs

Filamentous Identification

Biological Products

Wastewater Treatment Seminar

Sign up now for our Monthly Newsletter

Request for our new Brochures

Call now to set up a Wastewater Biomass Analyses or Filamentous Identification of your plant!

Finally new Release

Filamentous Identification

"the Easy Way"

New training program

With the summer months in progress and high temperatures on the rise, many locations are having problems with algae and duckweed growth.

Typical Problem areas:

Wastewater Treatment plants

Drinking Water Plants

Clarifiers

Aeration lagoons

Ornamental Ponds

De-Chlorination contact chambers

Lakes

Rivers

Oceans

Blue-green, red, yellow and brown colored algae in many ponds and lagoons has been more widespread than in previous years due to higher temperatures and less oxygen transfer in ponds and lagoons, lowered rainfall, and runoff interference.

Algae or tetrads growing in any aerated lagoon systems, ponds or wastewater treatment plants can increase both the TSS and the CBOD5 of the effluent. This can cause false high BOD and TSS levels in final effluent permits. Excess algae can also create nuisance surface scums, poor water clarity, and noxious odors. If the algae makes its way into the drinking water source, it also can impact taste.

Algae production is many times correlated to the levels and ratios of nitrogen (N) and phosphorous (P) in the water. Generally, a phosphate concentration of 0.01 mg./l will support plankton, while concentrations of 0.03 to 0.1 mg./l phosphate or higher will likely trigger algae blooms (USEPA, 1986; Dunne and Leopold, 1978).

Not all algae are alike though. Many times the algae or cyanobacteria and tetrads that grow in wastewater ponds and lagoons is often times due to an excess of BOD instead of excess nutrient levels. We have worked with papermills that actually are limited by nutrients, most often Nitrogen. This impacts the floc forming bacteria. Tetrads and cyanobacteria can fix nitrogen from the sunlight, so they will then overtake the lagoons and cause serious TSS problems. Addition of nitrogen to these lagoons based upon BOD loading made the problems disappear quickly. Normal floc forming bacteria can then grow, consume excess BOD and out-compete and starve out the algae and tetrads.

Algae are a source of food and energy for fish and other lake organisms and a vital part of all lakes. How do you balance too much or too little? Too much algae or the wrong type of nuisance algae, however, can interfere with lake uses by clogging the filters in water treatment plants, inhibiting the growth of other plants by clouding the water so that it shades them or out-competes with natural plant life. As the natural plant life then decays--more oxygen depletion occurs and fish kills increase. Some species of algae can also release toxins.

Excess algae can interfere with the simple pleasure of looking at a lake for its beauty. Unsightly scum is usually caused either by tangled masses of filamentous algae or by "blooms" of certain planktonic algae that float on the lake surface forming scums. The regular occurrence of visible algae blooms often indicates that nutrient levels, especially phosphorus, are too high.

Excessive plant growth can physically prevent mixing of oxygen through the water, plant die off can occur and fish kills can occur also with too much algae.

Cyanobacteria, better known as blue-green algae are often responsible for these phenomena.
Some health problems have been linked to these occurrences in many lakes and ponds where people and animals swim or cattle and animals that drink the water. They can absorb nitrogen from the atmosphere and transform it into ammonium or nitrates. At the end of the growing season the cyanobacteria die and release nutritive salts back into the water.

Algae is not always bad. Algae have been used to provide food for people and livestock, to serve as thickening agents in ice cream or shampoo, and can be used as drugs to ward off diseases. More than 150 species of algae are commercially important food sources, and over $2 billion of seaweed is consumed annually by humans, specifically in Japan.

Seaweed and kelp also are applied to soils as a fertilizer and soil conditioner, as their high concentrations of potassium and trace elements and micronutrients improve crop production, animal feed lots add them as a vitamin supplement, wastewater treatment plants add them as a micronutrient source for the bacteria.

So, how do you determine what type of algae or cyanobacteria you have? More importantly what is causing it and how do you get rid of it?

Testing of the pond or lagoon parameters can narrow down the cause. Microscopic analyses can narrow down whether it is algae or cyanobacteria. Duckweed can be visually identified.

Mixing, aeration, sunlight, CO₂, nutrients, excess BOD are all factors in algae growth in ponds, lagoons and wastewater treatment plants. Retention time is an influential factor controlling algal growth. As photosynthetic organisms, algae require light to grow, so sunlight and depth of the lagoons or ponds are also a factor.

Excess BOD is a main component since the carbon often is a food source for some of the cyanobacteria and algae that grow. Run- off from animals, pollution, leaves and plants decomposing are some of the sources of BOD. In industrial facility wastewater ponds, high BOD comes from the process side. A simple COD/BOD or TOC can tell if this is causing your problems. If BOD is over 5-10 ppm, then more than likely high BOD is the cause for some of the problems. If you have a treatment pond, or aeration basin, increase MLSS in order to consume any excess BOD.

Nutrients: Phosphorus and nitrogen

Plants require phosphorus and nitrogen for growth. The concentration of these substances in water and sediments control the total amount of plant matter that can grow.

In most lakes, phosphorus is the least available nutrient; so its abundance--or scarcity--controls the extent of algae growth. If more phosphorus is added to the lake from sewage treatment plants, urban or farmland runoff, lawn or garden fertilizers, septic tanks or other watershed or outside resources, or even if it is released from phosphorus-rich lake bottom sediments from plant die-off, more algae will grow. A simple test can be performed to measure the phosphorus concentration or nitrogen levels to determine if this is your problem in your lagoon. Another important parameter to check also should be pH.

Dissolved oxygen is critical in ponds and lagoons. Available oxygen is consumed through decomposition of plant and animal material. Oxygen transfer is also lower with higher temperatures. Drop a DO probe into the lagoon or pond and measure the Dissolved air.

Under certain conditions, especially when oxygen is absent from bottom waters, phosphorus is released from bottom sediments into the overlying water. In turn, algae clouds water clarity and decreases the depth of light penetration. If DO is too low, increase mixing and aeration with mechanical aerators, or you can use Mazzei venturie injectors in the lines to increase D.O. Chemicals such as sodium nitrate can be added as an alternate oxygen source when mechanical options are not practical.

Low Rainfall and high temperatures are often times a contributor to increased algae in ponds. Rain can tend to be a good dilution factor for pollutants. If there is no rain and high temperatures and high levels of evaporation, what normally is not considered polluted or high BOD becomes more concentrated and thereby, increases chances for algae growth.

· Herbicides and Algaecides, Copper Sulfate and Bleach are traditional chemical methods that have been used in the past.

· Fountains and Aeration help increase mixing and aeration and increase normal biological activity, thereby lessening the chance for algae to grow.

· Mechanical cutting and removal of aquatic weeds or harvesting of duckweed is common, but high on manpower

· Mechanical spraying or brushing of clarifiers, weirs and surface areas will significantly help with treatment plants and algae removal

· Physical covers of clarifiers

· Bacteria- The use of non-toxic, environmentally friendly biological products in lakes and ponds has become very popular recently because it is natural and involves no use of herbicides or algaecides. Bacteria out-compete with the algae for nutrients and carbon. If the proper environmental conditions are there, bacteria can grow quicker and more efficiently. The pond is cleaner and no toxic chemicals or residuals result. Bacteria are then added on a maintenance dosage to keep the algae from growing.

· Surface-growing plants such as duckweed can provide natural cover. Duckweed, if kept from the effluent by inserting surface baffles in front of the effluent weir, is very effective toward reducing algae in the lagoon. Water Hyacinths also help with BOD reduction.

This is a papermill that had serious problems with BOD, TSS and duckweed overgrowth. A biological program was implemented with some process control changes. The majority of the duckweed has disappeared and BOD and TSS are the best the plant has had in its history.

These are ponds at a tree farm in California

This is a winery in New Zealand

Here is a lagoon at a GunPowder plant.