Aeration

What can an operate do to minimize the consumption of power in aeration methods?

-don't over aerate -properly maintain pumps, motors and blowers -keep air diffusers clean and free of debris

What are the solutions to corrosion operating problems?

-don't over aerate (2-4mg/L) -apply protective coating to metallic surfaces

The normal air-to-water ratio during peak flow in a packed tower aerator is _______ to ________.

25 1

A carbon dioxide concentration of ______ mg/L will reduce the water's pH and make it more corrosive.

50

Volatile organic chemicals

A classification of volatile, manufactured, synthetic chemicals that are primarily used as industrial solvents.

Aerator

A device used to bring water and air into close contact

_____ _______ occurs when gases come out of solution in the media of a gravity filter due to excess DO in the water and a drop in pressure.

Air binding

The aeration systems using pressurized air are _____-______-_______ type aeration systems

Air-into-water

When CO2 levels are above the range of 5-15 mg/L, it can create problems, what are they?

CO2 reduces pH which makes the water corrosive Lower pH keeps iron in solution making it difficult to remove CO2 reacts with lime during the softening process and requires more chemical usage to achieve the desired hardness reduction.

_____, ______, and _______ control tests are routinely performed on aeration systems to determine if the system is operating correctly and efficiently.

DO, pH, and temperature

What operating problems are associated with floating floc?

If the water in a clarifier has been over-aerated, the dissolved gases may come out of solution and small bubbles will rise to the surface. These bubbles may be attached to the floc particles and cause them to float to the surface as well.

What do draft tube aerators accomplish?

Increase DO in existing basin or tank

How is CO2 removed from solution?

It is removed very easily and is removed by stripping action of the aeration process. All forms of aeration are effective at reducing CO2

Swamp gas is common name often substituted for _______

Methane

_______ is not very soluble in water which means that almost any form of aeration will remove it.

Methane

What are the operating problems associated with algae?

Slat-and-coke tray aerators and positive draft aerators are often to the air and sunlight which can promote algae or slime growth. This algae and slime growth can lead to other operational problems and increase organic loading.

Packed tower aeration is used to remove __________ from a water supply to meet regulatory requirements.

VOCs

Two main methods of aeration?

Water-into-air type air into-water type

How does aeration work?

accomplished by bringing air and water into contact with each other which enable oxygen in air to transfer into the water. The more surface area contact between the air and water, the more oxygen transfer takes place.

Hydrogen sulfide is easy removed by most forms of __________ because it comes out of solution very easily.

aeration

How are VOCs removed from water?

aeration is usually the most cost effective way to reduce VOC levels in groundwater. Most VOCs are not as easily removed from water as CO2 or H2S. A special aeration method called "packed tower aeration" is usually required to reduce VOCs to within legal limits.

How to remove iron and manganese from water

basic aeration process can effectively oxidize iron while manganese usually requires the use of a chemical oxidant or specialized aeration process. For this reason, aeration is typically used in applications where iron is the main concern due to low manganese concentrations.

What constituents are affected by aeration

carbon dioxide hydrogen sulfide methane volatile organic chemicals radon iron manganese tastes odors

Aeration occurs in the splash areas of a _________ aerator.

cascade

What are the types of Water-into-air type aeration?

cascade cone slat and coke tray draft spray packed towers

What are common operating problems?

corrosion floating floc filter air binding hydrogen sulfide removal algae clogged diffusers energy consumption

What are the types of Air-into-water type aeration?

diffuser draft tube mechanical pressure

What is the solution to floating floc operating problems?

don't over aerate

What is the solution to air binding operating problems?

don't over-aerate

A _______ ______ is more effective than the cone, cascade, and slat-and-coke-tray type of aerators when it comes to oxidizing iron and manganese and removing dissolved gases.

draft aerator

What can air diffusers become clogged with?

dust oil debris chemical deposits

Hazards of methane

extremely flammable and explosive at certain concentrations in air. it can also cause asphyxiation by displacing the oxygen in air. For these reasons, it is very important that when methane is removed from the water supply, it is adequately dissipated into the atmosphere.

Methane characteristics

groundwater that is located near natural gas deposits often have elevated levels of methane. It is colorless, odorless and tasteless in air but can cause water to have garlic taste when present in sufficient concentrations. It is not very soluble in water which means that almost any aeration method will remove it.

What are the operating problems associated with hydrogen sulfide removal?

hydrogen sulfide removal happens best when the water pH is <6. since normal groundwater pH is higher than 6, reducing pH to 6 using CO2 is a good solution. When the H2S is removed during the aeration process, the excess CO2 will also be removed which will return the pH to an acceptable level.

What do mechanical aerators accomplish?

increase DO levels

What do diffuser aerators accomplish?

increase DO to reduce poor tastes and odors

What are the goals of the aeration process?

increase the surface area of contact between the water and air. Provide a constant supply of air to provide maximum air to water transfer. The interface surface area is a key component of aeration.

What are the solutions to clogged air diffusers?

maintain clean air filters don't over-lubricate blowers prevent backflow into diffusers.

Iron and manganese

many groundwaters have elevated levels of iron and manganese which cause aesthetic problems for water suppliers. These two inorganic contaminants are removed through a process of oxidation which causes them to form a precipitate which can then be removed by settling or filtering.

Volatile organic chemical characteristics

many manufactured chemicals have found their way into the water supply. VOCs are regulated by the USEPA because they are either toxic, cause cancer, or are suspected of causing cancer.

Tastes and odors

organic materials that cause bad tastes and odors in water supplies can generally be easily oxidized by aeration. Some taste and odor causing compounds such as oils produce algae cannot be removed sufficiently by aeration and therefore require the use of chemical oxidants or GAC adsorption.

What do cascade aerators accomplish?

oxidize iron partially reduce dissolved gases

What do slat-and-coke tray aerators accomplish?

oxidize iron partially reduce dissolved gases

What do cone aerators accomplish?

oxidize iron partially reduced dissolved gases

What do spray aerators accomplish?

oxidize iron and manganese increase DO

What do pressure aerators accomplish?

oxidize iron and manganese increase DO levels

What do draft aerators accomplish?

oxidize iron and manganese reduce dissolved gases

________ ________ aerators may be regulated by the clean air act due to their gas discharges

packed tower

Radon

radioactive gas that is a decay product of uranium and may be found in certain groundwaters due to naturally occurring uranium deposits. main method of exposure is through inhalation and it is the second leading cause of lung cancer in the U.S. behind smoking.

What do packed tower aerators accomplish?

removal of VOCs

Hydrogen sulfide characteristics

responsible for rotten egg odor found in some groundwater supplies. It is both corrosive and poisonous and must be removed from the water. it is unstable and can be removed by almost any form of aeration because it comes out of solution very easily.

How is radon removed from water?

reverse osmosis ion exchange granular activated carbon packed tower aeration. * most effective

What is the solution to algae operating problems?

shade the aerators to minimize direct sunlight

Carbon dioxide is removed from water by the aeration process due to the _________ ____________, not oxidation

stripping action

Water ______ and gas solubility are inversely related which means that as ______ goes up, solubility goes down.

temperature temperature

Dissolved oxygen content in water

the amount of DO that water can keep in solution depends of the temperature and salinity. As the temperature goes up, solubility goes down. Cold water can hold more DO than warm water. The lower the salinity, the more DO the water can hold.

how much carbon dioxide is usually in water solution?

usually 1,700 mg/L at 68 degrees F water from deep wells usually contains <50 mg/L of CO2 shallow wells may have CO2 concentrations as high as 300 mg/L.

Dissolved oxygen

water that contains 2-4 mg/L of DO tastes better than water containing less than 1 mg/L of DO. Too much of a good thing can be a bad thing. Too much DO will cause the water to be corrosive because excess oxygen accelerate rate of corrosion.

What operating problems are associated with air binding?

when gases come out of solution in the media of a gravity filter, it can cause air binding which will prevent flow through the filter. The corrective action if this occurs is to backwash the filter to release the air from the media.

What operating problems are associated with corrosion?

when water and oxygen come into contact with metal surfaces, corrosion can occur. therefore, excessive levels of DO in a water system can cause corrosion problems.