An aerated lagoon (or aerated pond) is a simple

wastewater treatment Wastewater treatment is a process used to remove contaminants from wastewater and convert it into an effluent that can be returned to the water cycle. Once returned to the water cycle, the effluent creates an acceptable impact on the environm ...

system consisting of a

pond A pond is an area filled with water, either natural or artificial, that is smaller than a lake. Defining them to be less than in area, less than deep, and with less than 30% emergent vegetation helps in distinguishing their ecology from tha ...

with artificial

aeration Aeration (also called aerification or aeriation) is the process by which air is circulated through, mixed with or dissolved in a liquid or other substances that act as a fluid (such as soil). Aeration processes create additional surface area in ...

to promote the biological oxidation of

wastewater Wastewater is water generated after the use of freshwater, raw water, drinking water or saline water in a variety of deliberate applications or processes. Another definition of wastewater is "Used water from any combination of domestic, industrial ...

s. There are many other aerobic biological processes for treatment of wastewaters, for example

activated sludge The activated sludge process is a type of biological wastewater treatment process for treating sewage or industrial wastewaters using aeration and a biological floc composed of bacteria and protozoa. It uses air (or oxygen) and microorganism ...

trickling filter A trickling filter is a type of wastewater treatment system. It consists of a fixed bed of rocks, coke, gravel, slag, polyurethane foam, sphagnum peat moss, ceramic, or plastic media over which sewage or other wastewater flows downward and c ...

rotating biological contactor A rotating biological contactor or RBC is a biological fixed-film treatment process used in the secondary treatment of wastewater following primary treatment. The primary treatment process involves removal of grit, sand and coarse suspended mate ...

s and

biofilter Biofiltration is a pollution control technique using a bioreactor containing living material to capture and biologically degrade pollutants. Common uses include processing waste water, capturing harmful chemicals or silt from surface runoff, and ...

s. They all have in common the use of

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements ...

(or

air The atmosphere of Earth is the layer of gases, known collectively as air, retained by Earth's gravity that surrounds the planet and forms its planetary atmosphere. The atmosphere of Earth protects life on Earth by creating pressure allowing f ...

) and

microbial A microorganism, or microbe,, ''mikros'', "small") and ''organism'' from the el, ὀργανισμός, ''organismós'', "organism"). It is usually written as a single word but is sometimes hyphenated (''micro-organism''), especially in olde ...

action to reduce the pollutants in wastewaters.

Types

*Suspension mixed lagoons, where there is less energy provided by the aeration equipment to keep the sludge in suspension. *

Facultative lagoon Facultative lagoons are a type of waste stabilization pond used for biological treatment of industrial and domestic wastewater. Sewage or organic waste from food or fiber processing may be catabolized in a system of constructed ponds where adequate ...

s, where there is insufficient energy provided by the aeration equipment to keep the sludge in suspension and solids settle to the lagoon floor. The biodegradable solids in the settled sludge then degrade as in an

anaerobic lagoon An anaerobic lagoon or manure lagoon is a man-made outdoor earthen basin filled with animal waste that undergoes anaerobic respiration as part of a system designed to manage and treat refuse created by concentrated animal feeding operations (CAFOs). ...

Suspension mixed lagoons

Suspension mixed lagoons flow through

systems where the effluent has the same composition as the mixed liquor in the lagoon. Typically the sludge will have a residence time or sludge age of 1 to 5 days. This means that the

chemical oxygen demand In environmental chemistry, the chemical oxygen demand (COD) is an indicative measure of the amount of oxygen that can be consumed by reactions in a measured solution. It is commonly expressed in mass of oxygen consumed over volume of solution whic ...

(COD) removed is relatively little and the effluent is therefore unacceptable for discharge into receiving waters. The objective of the lagoon is therefore to act as a biologically assisted flocculator which converts the soluble biodegradable organics in the influent to a biomass which is able to settle as a sludge. Usually the effluent is then put in a second pond where the sludge can settle. The effluent can then be removed from the top with a low chemical oxygen demand, while the sludge accumulates on the floor and undergoes anaerobic stabilisation.

Methods of aerating lagoons or basins

There are many methods for aerating a lagoon or basin: * Motor-driven submerged or floating

jet aerators {{more citations needed, date=January 2021 Jet aerators are applied across a wide range of water, wastewater and biosolids treatment applications. Their primary purpose is to transfer oxygen to the liquid or sludge. A Jet aerator works through aspi ...

* Motor-driven floating surface aerators * Motor-driven fixed-in-place surface aerators * Injection of compressed air through submerged diffusers

Floating surface aerators

Ponds or basins using floating surface aerators achieve 80 to 90% removal of BOD with retention times of 1 to 10 days.Available at CSA Illumina website
The ponds or basins may range in depth from 1.5 to 5.0 meters. In a surface-aerated system, the aerators provide two functions: they transfer air into the basins required by the biological oxidation reactions, and they provide the mixing required for dispersing the air and for contacting the reactants (that is, oxygen, wastewater and microbes). Typically, the floating high speed surface aerators are rated to deliver the amount of air equivalent to 1 to 1.2 kg O₂/ kWh. However, they do not provide as good mixing as is normally achieved in activated sludge systems and therefore aerated basins do not achieve the same performance level as activated sludge units. With low speed surface aerators SOTE (Standard Oxygen Transfer Efficiency) is higher thanks to better mixing capacity. This mixing capacity of an impeller depends highly on the impeller diameter. Low speed surface aerator present such high diameter. Therefore SOTE for low speed surface aerators is about 2 to 2.5 kg O₂/kWh. This is why low speed surface aerators are mostly used in sewage or industrial treatment as WWTP are bigger and sparing energy becomes very interesting. Biological oxidation processes are sensitive to temperature and, between 0 °C and 40 °C, the rate of biological reactions increase with temperature. Most surface aerated vessels operate at between 4 °C and 32 °C.

Submerged diffused aeration

Submerged diffused air is essentially a form of a

diffuser Diffuser may refer to: Aerodynamics * Diffuser (automotive), a shaped section of a car's underbody which improves the car's aerodynamic properties * Part of a jet engine air intake, especially when operated at supersonic speeds * The channel bet ...

grid inside a lagoon. There are two main types of submerged diffused aeration systems for lagoon applications: floating lateral and submerged lateral. Both these systems utilize fine or medium bubble diffusers to provide aeration and mixing to the process water. The diffusers can be suspended slightly above the lagoon floor or may rest on the bottom. Flexible airline or weighted air hose supplies air to the diffuser unit from the air lateral (either floating or submerged).Floating Lateral Systems>

References

External links

Wastewater Lagoon Systems in Maine

Aerated, Partial Mix Lagoons
(Wastewater Technology Fact Sheet by the

U.S. Environmental Protection Agency The Environmental Protection Agency (EPA) is an Independent agencies of the United States government, independent executive agency of the United States federal government tasked with environmental protection matters. President Richard Nixon pro ...

)
Aerated Lagoon Technology
(Linvil G. Rich, Professor Emeritus, Department of Environmental Engineering and Science,

Clemson University Clemson University () is a public land-grant research university in Clemson, South Carolina. Founded in 1889, Clemson is the second-largest university in the student population in South Carolina. For the fall 2019 semester, the university enr ...

) {{Wastewater Waste treatment technology