Operation of Wastewater Treatment Plants Volume I Seventh Edition

Wastewater

A community's used water and water-carried solids (including used water from industrial processes) that flow to a treatment plant. Storm water surface water, and groundwater infiltration also may be included in the wastewater that enters a wastewater treatment plant. the term sewage usually refers to household wastes, but this word is being replaced by the term wastewater.

Receiving water

A stream, river, lake, ocean, or other surface or groundwater into which treated or untreated wastewater is discharged.

Wastwater is the same thing as

sewage

Which of these (could be more than one) does an operator do? A. Collect Samples B. Lubricate equipment

C. Record data

A,B,C

Who of these (could be more than one) employs treatment plant operators? A. Cities B. Sanitation Districts C. Industries

A,B,C

How did many receiving waters become polluted?

Receiving waters became polluted by a lack of public concern for the impact of waste discharges and by discharging wastewater into a receiving water beyond its natural purification capacity.

Why must municipal and industrial wastewaters receive adequate treatment?

Municipal and industrial wastewaters must receive adequate treatment to protect receiving water users.

Effluent

Water or other liquid-raw(untreated), partially treated, or completely treated- flowing FROM a reservoir, basin, treatment process, or treatment plant.

Why is it important that the operator be present during the construction of a new plant?

The operator should be present during the construction of a new plant in order to become familiar with the plant before the operator begins operating it.

How does the operator become involved i public relations?

The operator becomes involved in public relations by explaining the purpose and operation of the plant to visitors, civic organizations, school classes, news reporters, and city or district representatives.

Organic Waste

waste material that may come from animal or plant sources. Natural organic wastes generally can be consumed by bacteria and other small organisms. manufactured or synthetic organic wastes from metal finishing, chemical manufacturing, and petroleum industries may not normally be consumed by bacteria and other organisms.

Inorganic Waste

Waste material such as sand, salt, iron, calcium, and other mineral materials that are only slightly affected by the action of organisms. inorganic wastes are chemical substances of mineral origin; whereas organic wastes are chemical substances usually of animal or plant origin.

Primary Treatment

A wastewater treatment process that takes place in a rectangular or circular tank and allows those substances in wastewater that readily settle or float to be separated from the wastewater being treated. a septic tank is also considered primary treatment.

How does water pick up dissolved substances?

Water picks up dissolved substances as it falls as rain, flows over land, and is used form domestic, industrial, agricultural, and recreational purposes.

What are some of the dissolved substances in water?

Some of the dissolved substances in water include hydrogen, oxygen, calcium, carbon, magnesium, sodium, chloride, sulfate, iron, nitrogen, phosphorus, and organic material.

Which of these (could be more than one) contain significant quantities of organic material? A. Domestic wastewater B. Cooling water from thermal power stations C. Paper mill wastes D. Metal plating wastes E. Tanning wastes

A,C,E

List Four Types of Pollution

Organic Wastes, Inorganic Wastes, Radioactive Waste, and Thermal (heated) Wastes

Milligrams per Liter, mg/L

A measure of the concentration by weight of a substance per unit volume in water or wastewater. in reporting the results of water and wastewater analysis, mg/L is preferred to the unit parts per million (ppm), to which it is approximately equivalent.

Aerobic Bacteria

Bacteria that will live and reproduce only in an environment containing oxygen that is available for their respiration (breathing), namely atmospheric oxygen or oxygen dissolved in water. Oxygen combined chemically, such as in water molecules (H2O), cannot be used for respiration by aerobic bacteria.

Secondary Treatment

A wastewater treatment process used to convert dissolved or suspended materials into a form more readily separated from the water being treated. usually, the process follows primary treatment by sedimentation. The process commonly is a type of biological treatment followed by secondary classifiers that allow the solids to settle out from the water being treated.

Stabilization

Conversion to a form that resists change. organic material is stabilized by bacteria that convert the material to gases and other relatively inert substances. Stabilized organic material generally will not give off obnoxious odors.

Anaerobic Bacteria

Bacteria the live and reproduce in an environment containing no free or dissolved oxygen. Anaerobic bacteria obtain their oxygen supply by breaking down chemical compounds that contain oxygen, such as sulfate (SO42-).

What causes oxygen depletion when organic wastes are discharged to the water?

Organic wastes in water provide food for the bacteria. these bacteria require oxygen to survive and consequently deplete the oxygen in the water in a way similar to the way oxygen is removed from air when people breathe.

What kind of bacteria caused hydrogen sulfide gas to be released?

Anaerobic Bacteria

Pathogenic Organisms

Bacteria, viruses, cysts, or protozoa that can cause disease in a host (such as a person). There are many types of organisms that do not cause disease and are not called pathogenic. Many beneficial bacteria are found in wastewater treatment processes actively cleaning up organic wastes.

What are some examples of diseases that may be spread through wastewater discharges?

Typhoid, cholera, dysentery, polio, hepatitis (Jaundice), giardiasis (giardia), cyptosporidiosis (crypto)

Disinfection

The process designed to kill or inactivate most microorganisms in water or wastewater, including essentially all pathogenic (disease-causing) bacteria There are several ways to disinfect, with chlorination being the most frequently used in water and waste water treatment plants.

pH

Technically, this is the logarithm of the reciprocal of the hydrogen ion concentration. pH expresses the intensity of the acidic or basic condition of a liquid. The pH may range from 0-14, where 0 is most acidic, 14 is most basic, and 7 is neutral. Most natural waters have a pH between 6.5 and 8.5

Nutrients

any substance that is assimilated (taken in) by organisms and promotes growth. Nitrogen and phosphorus are nutrients that promote the growth of algae. There are other essential and trace elements that are also considered nutrients.

Algae

Microscopic plants containing chlorophyll that live floating or suspended in water. they also may be attached to structures, rocks, or other submerged surfaces. Excess algal growths can impart tastes and odors to potable water. Algae produce oxygen during sunlight hours and use oxygen during the night hours. their biological activities appreciably affect the pH, alkalinity, and dissolved oxygen of the water.

Where do the disease-causing bacteria in wastewater come from?

Body wastes of Humans who have diseases

What is the term that means "disease-causing"?

Pathogenic

What is the most frequenly used means of disinfecting treated wastewater?

Chlorination

Total Solids

Dissolved + Suspended solids = Total Solids

Dissolved Solids

imagine a filter, dissolved solids will pass through filter with the water

Suspended solids

imagine a filter, suspended solids will be caught on the filter

How to find the weight of dissolved solids

After filtering the suspended solids and weighing those, you then evaporate the water and weigh the residue to determine the dissolved solids weight

What are the two parts of suspended solids

settleable, nonsettleable

what is difference between settleable and nonsettleable solids

depends on size, shape, and weight per unit volume of the solid particles; large-sized particles tend to settle more rapidly than smaller particles

How to calculate weight of nonsettleable solids

(settleable solids + Dissolved Solids) - Total Solids= Nonsettleable solids

Total Solids consist of __________ and _________ Solids, both of which contain organic and inorganic matter.

Dissolved and Suspended

Why is it necessary to measure settleable solids?

Settleable solids must be measured to determine the efficiency of settling basins. This amount must also be known to calculate loads on settling basins, sludge pumps, and sludge handling facilities for design and operational purposes. ( you should have recognized the need to know the efficiency of settling basins)

A Imhoff cone is used to measure __________ solids.

Settleable

Imhoff Cone

A clear, cone shaped container marked with graduations. The cone is used to measure the volume of settleable solids in a specific volume (usually one liter) of water or wastewater.

Receiving Waters

a stream, river, lake, ocean, or other surface or groundwater into which treated or untreated wastewater is discharged.

Whether any problems are caused in the receiving waters depends on what factors

1.Type of degree of treatment

2.Size of flow from the treatment plant

3.Characteristics of wastewater from the treatment plant

4.Amount of flow in the receiving stream or volume of receiving lake that can be used for dilution

5. Quality of the receiving waters

6. amount of mixing between the effluent and receiving waters

7. uses of the receiving waters

Transpiration

the process by which water vapor is released to the atmosphere by living plants. This process is similar to people sweating.

Nutrient Cycles

the transformation or change of a nutrient from one form to another until the nutrient has returned to the original form, thus completing the cycle. the cycle may take place under either aerobic or anaerobic conditions.

Septic

a condition produced by anaerobic bacteria. if severe, the sludge produces hydrogen sulfide, turns black gives off foul odors, contains little to no dissolved oxygen, and the wastewater has a high oxygen demand.

NPDES

National Pollutant Discharge Elimination System

What is required under the Federal Water Pollution Control Act

NPDES permits

BOD

Biochemical Oxygen Demand.

Biochemical Oxygen Demand (BOD)

The rate at which organisms use the oxygen in water or wastewater while stabilizing decomposable organic matter under aerobic conditions. In decomposition, organic matter serves as food for the bacteria and energy results from its oxidation. BOD measurements are used as a surrogate measure of the organic strength of wastes in water.

Coliform

A group of bacteria found in the intestines of warm blooded animals (including humans) and also in plants, soil, air, and water. the presence of coliform bacteria is an indication that the water is polluted and may contain pathogenic organisms. Fecal coliforms are those coliforms found in the feces of various warmblooded animals, whereas the term coliform also includes other environmental sources.

Why should an operator have an understanding of natural cycles?

Operators need an understanding of natural cycles in order to control wastewater treatment processes and odors and also to protect receiving waters.

What can happen when nutrient cycles are disrupted and there is no dissolved oxygen in the receiving waters?

When nutrient cycles become disrupted and there is no dissolved oxygen in the receiving water, these wasters become septic, stink and look terrible.

Three major components or parts of facilities handling wastewater

Collection, treatment, discharge or reuse

influent

waster or other liquid--raw (untreated) or partially treated-- flowing into ta reservoir, basin, treatment process, or treatment plant.

what is the "aging problem"

waste taking too long to get to plant can have anaerobic bacteria feeding on the wastes making the odor problems, damaging concrete in your plant and make the wastes more difficult to treat from not settling easily.

sanitary sewer

a pipe or conduit intended to carry wastewater or waterborne wastes from homes, businesses, and industries to the treatment works. stormwater runoff or unpolluted water should be collected and transported in a separate system of pipes or conduits to natural watercourses.

storm sewer

a separate pipe, conduit or open channel that carries runoff from storms, surface drainage, and street wash, but does not include domestic and industrial wastes. storm sewers are often the recipients of hazardous or toxic substance due to the illegal dumping of hazardous wastes or spills caused by accidents involving vehicles transporting these substances.

what type of water goes down a storm sewer

all storm runoff from streets, land, and roofs of buildings

where does a storm sewer discharge?

watercourse without treatment

combined sewer

a sewer designed to carry both sanitary wastewaters and storm water or surface water runoff.

infiltration

the seepage of ground water into a sewer system, including service connections. seepage frequently occurs through defective or cracked pipes, pipe joints and connections, interceptor access risers and covers, or manhole walls.

Separation of combined sewers into sanitary and storm sewers is....

very costly and difficult to accomplish

lift station

placed where low areas of land must be sewered or where pipe depth under the ground surface becomes excessive. Lift station bring wastewater to a higher point form which it may again flow by gravity or the wastewater may be pumped under pressure directly to the treatment plant.

Why should the operator be familiar with the wastewater collection and transportation network?

By knowing the origin of wastes reaching the plant, the time it takes, and how the wastes are transported (flow by gravity or by gravity and pumping), the operator will be able to sport troubles and take corrective action.

What problems may occur when it takes a long time from wastewater to flow through the collection sewers to the treatment plant?

when it takes a long time hydrogen sulfide gas may be released by anaerobic bacteria feeding on the wastes. this can cause odor problems, damage concrete in the plant ,and make the wastes more difficult to treat such as solids no settling easily.

List three types of sewers

sanitary, storm, combined

Why are combined sewers a problem?

In a system using combined sewers, flows sometimes may become overloaded during storms due to inadequate capacity. this could allow partially treated wastes to be discharged into receiving waters as a result of attempting to treat extreme hydraulic (flow) overloads.

Preliminary Treatment process consists of

screening, grit removal, pre-aeration, flowmeter

screening

removes roots, rags, cans, and large debris (haul to a landfill or, if possible, grind and return to plant flow)

Grit removal

removes sand and gravel (haul to a landfill)

Pre-aeration

freshens wastewater and helps remove oil

Flowmeter

measures and records flow

Primary Treatment consists of

Sedimentation and flotation

Sedimentation and flotation

removes settleable and floatable material

secondary treatment consists of

solids handling, biological, chemical, and physical processes, disinfection, effluent

solids handling

treats solids removed by other processes

biological chemical and physical processes

removes suspended and dissolved soldis

disinfection

kills pathogenic organisms

primary treatment does what

some of the solids matter carried b wastewater will settle out or float to the water surface where it can be separated from wastewater being treated

secondary treatment processes consist of

biological processes. this is where organisms living in a controlled environment of the process are used to partially stabilize (oxidize) organic matter not removed by previous treatment processes and to convert it into a form that is easier to remove from the water.

where does waste material removed go

solids handling facilities then to ultimate disposal

SO2

Sulfur dioxide

What is used to help disinfect before discharge

chlorine, and sulfur dioxide may be added to effluent to neutralize the chlorine to detoxify the effluent

Shredding

a mechanical treatment process that cuts large pieces of wastes into smaller pieces so they will not plug pipes or damage equipment. shredding and comminution usually mean the same thing.

bar screen

to protect equipment and reduce any interference with inplant flow, debris and trash removed by bar screen. parallel bars placed at an angle in a channel and cleaned by hand or mechanical means.

Two common devices for shredding

barminutor and comminutor

Shredding device follow after what

bar screen

Most sewer pipes are laid at a slope steep enough o maintain a wastewater flow of ___________ to prevent ________ from settling in the pipes.

2 feet per second. Grit

Grit

The heavy material present in wastewater such as sand, coffee grounds, eggshells, gravel and cinders. Also called DETRITUS.

Why should Grit be removed early in the treatment process?

Because it is abrasive and will rapidly wear out pumps and other equipment. It is inorganic and cannot be broken down by any biological treatment process.

How is Grit usually removed?

in a long, narrow trough called a grit channel.

Grit Channel is designed to provide a flowthrough velocity of ______________.

1 foot per ssecond

Grit washer

some plants have grit washers that remove some of the organic material from the grit so that organic solids can remain in the main waste flow to be treated.

aerated grit chambers

compressed air is added through diffusers to provide better separation of grit and other solids. Aeration helps prevent odors and assist the biological treatment process

What is usually done with grit that has been removed from the wastewater?

Grit removed from the wastewater is usually buried to avoid nuisance conditions

Headworks

the facilities where wastewater enters a wastewater treatment plant. The headworks may consist of bar screens, comminutors a wet well, and pumps.