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OIT
| Question | Answer |
|---|---|
| What is preliminary treatment | Pretreatment of primary treatment removes material s that can be easily collected from the raw sewage before they damage or clog the pumps and sewage lines of the primary treatment clarfiers, trash, tree limbs leaves, branches. |
| Tertiary Treatment | Tertiary treatment is the next wastewater treatment process after secondary treatment. This step removes stubborn contaminants that secondary treatment was not able to clean up. |
| What is sewage treatment | Sewage treatment is the process of removing contaminants from waste water and household sewage, |
| What is screening used for? | The influent passes through a bar screen to remove all large objects like, cans, plastic packets, rags, sticks, etc. |
| How is the screening done? | With a mechanical raked bar screen |
| What happens to the solids collected on a bar screen | Landfill or incineration |
| Why is a bar screen necessary | Bar screening is neccessary because if gross solids are not removed they become entrained in pipes and and moving parts of the treatment plant and can cause substantial damage and inefficiency in the process. |
| What is grit removal? | Grit removal is a pretreatment process which may include a grit channel or chamber where the velocity of the incoming sewage is slowed to allow for the sand, grit, stones, broken glass to settle out. |
| What are the 3 types of grit chambers? | horizontal grit chambers, aerated grit chambers and vortex grit chambers. |
| WWhat is primary treatment? | Primary treatment is the primary sedimentation stage, sewage flows through large tanks called settling basins, sedimentation tanks or primary clarifiers. |
| What are primary clarifiers used for? | Prim clarifiers are used to settle sludge while grease and oil float to the top and are skimmed off. |
| Define microorganisms | Microorg. are plants, animals and other living organisms which cannot be seen by the naked eye. |
| What are some examples of micro organisms? | bacteria, algae, viruses |
| what are bacteria that aid in digestion, the production of beer cheese and bread? | non pathogenic |
| What is a pathogenic organisms | Pathogenic org cause disease in humans and are pathogens |
| Where are micro org found? | They are found in surface water, originate from improperly treated sewage, storm water runoff, septic beds, farm manure, and other natural sources |
| What is disinfection? | Water that has been treated and has had pathogens eliminated can be said to be disinfected. |
| What other things does the water treatment plant treat? | Pesticides, organic chemicals, heavy metals, and ions such as cyanide. |
| what other role do micro orgs. play in water treatment | they break down complex organic substances found in waste water into simpler compounds such as methane, co2 nitrates phosphates and water. |
| Why is it important to monitor temp, do, ph and toxin levels, nutrients. | Most micro orgs. can only live in a limited range of conditions, and it is important to maintain these conditions in a biological treatment process. |
| What two chemical is raw sewage high in? | Sewage has high nitrogen, phosphorous levels. |
| What can happen in raw sewage enters into surface water or streams? | Excessive amounts of these chemicals will lead to increases in the population of algae and other microrganisms. |
| Why is it a problem if we increase algae and microorganisms in a stream or lake? | These organisms will in turn deplete the amount of 02 in the water causing the death of fish and other animals and plants. |
| What is the other problem,besides the fertilizer effect if sewage is discharged into water? | Heavy metals and other toxins will lead to severe environmental damage. High levels of suspended solids can also result in habitat destruction of streams and rivers and lakes. |
| What is matter | Matter refers to anything which occupies space and has a mass |
| what is chemistry | chem may be defined as the science that deals with composition, properties and changes undergone by matter under certain conditions. |
| Matter exists in which states/ | gas, solid, liquid, depending on temperature or pressure. |
| What is the basic building block of all matter | the Atom |
| Each type of atom is known as | an element |
| what is a compound | when 2 elements combine they are called a compound |
| define chemical change | A chemical change occurs when a compound is altered to form a new compound, ie. the burning of fuel. |
| what is an organic compound | compounds which have carbon, hydrogen, oxygen and other elements are called organic compounds |
| What is inorganic compound | compounds that contain no carbon |
| What is it called when a compound undergoes a chemical change | a chemical reaction chlorine + water = Hypochlorous acid + Hydrochloric acid |
| what factors will cause chem reaction to speed up or slow down? | temp, pressure, and pH |
| what is oxidation | Oxidation is the addition of oxygen, removal of hydrogen, or the removal of electrons from an element of compound. |
| What are acids bases and salts used for in the water treatment process | Acids, bases, salts are commonly used for pH adjustment, flocculation, sedimentation, disinfection, corrosion control, water softening, and taste and color and odor control. |
| What happens if a salt acid or base is added to water/ | If a salt acid or base is added to water the compound will split into 2 separate parts, and is said to have disassociated. |
| What does an acid do? | An acid is a compound that releases hydrogen ions when it dissociates |
| What does a base do | When a base is added to water it dissociates and releases hydroxyl ions (OH) |
| What does a salt do | A salt will release hydrogen or hydroxyl ions when it dissociates. |
| what is meant by acidity and alkalinity | Acidity and alkalinity are terms used to describe a waters ability to buffer an acid or base respectably. |
| What is a solution | A solution is made up of two or more different parts |
| What are the 2 parts of the solution | the solvent and the solute |
| What is the solvent | the solvent is the component that dissolves other components |
| what is the solute | the solute is the component that is disolved |
| What is concentration | The concentration of a solution refers to the amount of solute dissolved in the solvent. |
| What are the three methods of measuring concentration of a solution | molarity, normality, and calculating the mass of the solute as a percent of the total mass of the solution. |
| Activated carbon what is it used for? | Activated carbon is very porous, and is used to adsorb particles from water. |
| what is adsorption | adsorption is a process where particles are trapped on the surface of the material. |
| What makes activated carbon better? | The high surface area of activated carbon allows it to remove soluble and colloidal materials which sand filters cannot. |
| What is alum or aluminum sulphate used for? | Alum is used as a chemical coagulant. It reacts with water and destabilizes suspended particles allowing them to form together and create floc. |
| Chlorine | Chlorine is a disinfectant and comes as a liquid, sodium hypochlorite, (powder) calcium hypochlorite or chlorine gas. |
| Why is chlorine good | Chlorine is an effective low cost method of disinfection. |
| What is dosage? | Dosage refers to how much chlorine is needed in the water |
| what is contact time? | contact time is the amount of time required for disinfection to occur. |
| What is chlorine demand? | When cl is first added it will combine with organic and inorganic compounds. The amount of chlorine required to combine with these compounds is called chlorine demand. |
| What is combined chlorine | some of the chlorine when added to water will combine with ammonia and create what is called combined chlorine. |
| What is free chlorine | Free chlorine is chlorine that does not combine with other compounds. |
| what is the chlorine residual? | The chlorine residual is the sum of the combined chlorine compounds and free chlorine. |
| Chlorine dosage = | Chlorine demand + chlorine residual |
| Chlorine residual = | Combined chlorine + free chlorine |
| What does 129/04 cover | The licensing of sewage works operators, for waste water treatment and waste water collection. |
| What is the O reg that describes the operational checks and sampling requirements for municipal drinking water systems | O reg. 170/03 |
| Under what reg. do operators require a license to work as an operator in a waste water treatment and collection system | O reg 129/04 |
| Under what reg. do operators require a license to work as an operator in a water treatment and distribution system? | O reg 128/04 |
| What can you not do in a water treatment facility without supervision, | Until OIT is passed you may not adjust a process, change flows, or adjust chemical dosing under directly supervised by a licensed certified operator. |
| what legislation addresses water treatment testing/sampling? | 170/03 |
| what legislation Addresses the licensing of sewage treatment plant operators? | 129/04 |
| what legislation addresses the certification of water system operators and water quality analysts. | 128/04 |
| Drinking water is legislated under what four acts? | Safe drinking water act, Ontario drinking water quality standards, drinking water systems, clean water resources act, and the Ontario water resources act |
| which regulation provides the minimum level of drinking water quality acceptable for human consumption? | O reg 169/03 Ontario drinking water quality standards |
| Which Ontario regulation identifies the minimum treatment reqs. for gwater and surface water sources? | O reg 170/03 sdwa |
| what is chlorine contact time? | The period of time needed for chlorine to sufficiently react with water and inactivate pathogens. |
| How are tri-halo methane's produced? | THMS are produced when chlorine when chlorine reacts with organic material. |
| Under what reg are disinfection req. described. | 0 reg. 170/03 |
| What is 4 log | 99.99 % pathogens removed |
| what is 3 log | 99.9 % |
| what is 2 log | 99 % |
| what is 1 log | 90% |
| What is .5 log | 68 % |
| What are the 7 sewage treatment components in order? | Screen, Grit separation, Primary clarifier, aeration tank, secondary clarifier, tertiary treatment, effluent disinfection |
| what are the preliminary treatments in a sewage plant? | Screen and grit separation and primary clarifier |
| What is secondary treatment | aeration tank and secondary clarifier |
| what are the last 2 parts of the sewage treatment process | tertiary treatment and disinfection, |
| What is the first step in the sewage treatment process? | Sewage entering the wpcp passes through devices designed to remove or reduce in size the large solids, grease, scum and grit before it enters further treatment processes. |
| How are large particles removed from the stream? | Coarse screens are used to to remove large objects |
| What is communition | The chopping or grinding of large particles in the waste stream. |
| What is the purpose of a grit chamber? | Sand, eggshells, stone and gravel is removed in grit channels or chambers. |
| why is it necessary to remove screen and remove grit? | It is necessary to that large objects or grit do not damage piping or equipment in the treatment facility. |
| What is primary treatment? | In some systems the waste water flows to a primary settling basin or primary clarifer, velocity is slowed heavy material settles or float tot he surface and are removed. |
| What happens to the material in the primary clarifier? | The settled and floated material is removed and sent to a sludge handling facility, while the liquid proceeds to secondary treatment. |
| What is the process relied upon in the primary clarifier process? | This process relies on gravity to separate material from the liquid. |
| How effective is primary treatment? | Primary treatment will remove 30 to 40 % bod and 40 to 60 5 suspended solids from the sewage. |
| What is secondary treatment in a sewage plant | After large particles have been removed,the effluent is sent to an aeration tank where it is aerated and mixed with a biological mass (activated sludge) where it consumes the bod as food. |
| What are the surface aerators or diffusers used for? | the organism are aerobic and require dissolved oxygen to survive so air is added to the mix. |
| What is mixed liquor? | Mixed liquor is a mixture of raw or settled waste water and activated sludge contained in an aeration basin in the activated sludge process |
| What is MLSS | Mixed liquor suspended solids (MLSS) is the concentration of suspended solids in mixed liquor, usually expressed in milligrams per liter (mg/l). |
| What is the next step after the secondary treatment? | The effluent, now a mixture of waste water and microorganisms is (mixed liquor) sent to 2ndary clarifiers where the sludge and susp material settle out. |
| What happens to the activated sludge after it settles out in the 2ndary clarifier? | It is pumped back into the aeration basins to maintain the level of activated sludge. |
| What is a sequencing batch reactor? | An SBR is a fill and draw activated sludge treatment system. Both aeration and secondary treatment is carried out in the same tank. |
| what is the process in an SBR | FILL, REACT (AERATION), SETTLE, DRAW (DECANT) AND IDLE. |
| What is ras | (RAS) return activated sludge, is continuously pumped back into the secondary biological treatment tank as part of the treatment process. |
| What is was | WAS Excess from the settled sludge, which is waste activated sludge (WAS), is pumped to the sludge handling process. |
| What is a trickling filter? | |
| what does preliminary treatment include? | Screens (coarse and/or fine) Comminutors (grinders) Grit removal units Pre-aeration (not always) |
| what size are coarse screens | May also be called a “trash rack” Three quarters of an inch to 6 inches |
| what size are fine screens | Less than three quarters of an inch |
| Why is it necessary to clean screens regularly? | Screens should be cleaned regularly to prevent headloss, septic action upstream, overloading sewers, shocking plant when screens clear |
| why is grit removal important | Installed after screening equipment to protect equipment from abrasion, avoid pipe clogging and reduce sedimentation load on clarifier |
| Types of grit removal equipment include | Grit channels Aerated grit channels Detritus tank Centrifugal separator |
| what is a commutor | A shredding device that grinds material to a size suitable to pass through fine screens in the unit |
| what is pre aeration | may proceed or follow screens and grit chambers designed for detention of 5 to 15 minutes for grease removal |
| wwhat is the purpose of pre aeration | removes gases from sewage, hydrogen sulphide which creates odor problems and increases chlorine demand, |
| what else does pre aeration do? | promotes flotation of grease and aids in skimmin, and aids coagulation for higher settling rates. |
| what is primary treatment | prim treat. remove settleeable solids reduce suspended solids from 40 - to 70 % |
| what are the primary units in primary treatment | Sedimentation tanks, (clarifiers) and waste stabilization ponds |
| what are three ancillary units for primary treatment | Vacuum filters, chlorination facilities, and sludge drying beds. |
| what is the role of the primary clariifer | Primary clarifiers remove the remaining settleable solids in raw sewage |
| what is the principles behind the primary clarifier | Principle is to slow down sewage as it moves through the tank allowing settleable solids enough time to settle out |
| what is the purpose of digestion | The purpose of digestion is to stabilze the complex organic matter in raw sludge into a simpler non-objectionable state (destroys pathogens, reduces odour |
| WWhat is the other purpose of digestion | Digestion reduces the volume of sludge, thus minimizing pumping and storage requirements and lowering costs. |
| What other things can digestion do? | Reduce mass of sludge' Produce a sludge that easier to dewater making it more suitable to lagooning Produces gas which can be used for heating |
| What is the prime objective of treating sludge | The objective of treating sludge is to stabilize the sludge so that there is a low oxygen demand. |
| What is sludge | Sludge refers to the residual, semi-solid material left from industrial wastewater, or sewage treatment processes. |
| What is a common method of treating sludge | Anerobic digestion |
| Describe anerobic digestion | Raw sludge which has settled in the primary and secondary clarifiers is wasted to anaerobic sludge digesters. |
| What happens to the sludge in an anerobic digester? | The sludge remains there for several weeks, during this time, anaerobic bacteria break down the solids to methane, co2 and inert solids. |
| what is another method of sludge digestion | Aerobic. in this process aerobic microorg. used in the activated sludge process further breakdown the sludge. |
| What happens to the sludge when its removed from the anaerobic or aerobic dig-esters? | The sludge is treated to remove water, sometimes chem. are added to aid in de-watering, |
| what are some common methods of de-watering? | Vacuum filtering, centrifuging, pressing or drying beds. |
| What is the final state of sludge called? | Bio solids, that may be land filled or spread on agricultural lands. Some bio solids are incinerated due to high transp. costs or heavy metal content. Sludge may also be composted. |
| What is the most important process in drink water treatment? | Disinfection |
| Disinfection = ________? | removal and inactivation |
| How are pathogens removed | pathogens are removed by chemically assisted filtration. |
| How is inactivation accomplished? | Inactivation is accomplished through use of chlorine or ozone, or with UV light. |
| When does inactivation occur? | After filtration so pathogens are not shielded by particulate. |
| What is chlorine contact time | The amount of time required for the chlorine to react with the water and inactivate the pathogens. |
| what is the name of the structure that holds the chlorine that inactivates the pathogens | The contact chamber. |
| What is an advantage of chlorine as a disifectant | Chlorine has a long disinfection time, it can disinfect long after it was applied. |
| Under what leg. are drinking disinfection requirements stated: | O. Reg. 170/03 |
| What is a 4 log, 3 log, 2 log, 1 log | 99.99 %, 99.9 % 99 % 90 % 68 % |
| what are the stages in a sewage treatment plant | screening, grit separation, primary clarifiers aeration tanks, secondary clarifiers, tertiary treatment,disinfection |
| Where does the sludge go after the primary clarifier? | the primary sludge goes either the digestion process or to disposal. |
| what happens in a primary clarifer | flow velocity is slowed so that solids can settle or float to the surface. |
| what amount of bod is removed during the primary clarifier process | 30 to 40 % |
| What is the percentage of suspended solids that are removed from the sewage during the primary clarifier stage | 40 to 60 % |
| What is secondary treatment | Even after prim. treatment most wastewater will contain large amount of dissolved or unsettled impurities, and used aerobic bacteria to break particles further. |
| How much bod is removed during the 2ndary process? | 80 to 90 % |
| Describe a 2ndary treatment process | ASP or activated sludge uses a bacterial mass in an aeration tank to break down material in the effluent. |
| What does the bacteria use as food? | BOD |
| Why must air be added to the tank | the bacteria need dissolved o2 to survive. |
| What is mixed liqour. | the mix of microorganisms and waste water |
| What happens in the 2ndary clarifier | the mixed liquor is sent to the 2nd clarifier where the activated sludge and other susp. material settle out. |
| What happens to the material that settles out in the 2ndary clarifier | Some of the material that settles out is sent back to the aeration basins to maintain the mass of activated sludge and the remaining sludge is sent to sludge handling facilities. |
| what are the 2 main parts of a typical asp system | An aeration tank, and secondary clarifier. |
| What is an SBR or sequencing batch reactor | An SBR |
| what is the process after the secondary clarifier | The process after the secondary clarifier is disinfection |
| How is chlorine neutralized before sending effleunt back to water source | chlorine is de chlorinated by adding sulphur dioxide or sodium bisulphat. |
| what are some other methods of disinfection | ozone, UV, |
| what may waste water include? | Waste water may include domestic sewage, industrial or commercial effluent. |
| How does waste water get to the wpcp | The waste water is removed through the use of sanitary sewers. sewers which transport storm runnoff are called storm sewers. |
| what is a combined sewer | A combined sewer is an older style of sewer system where waste water and storm water where carried in the same sewer. |
| what are sewers commonly made of? | Asbestos concrete, Polyvinyl chloride, or ductile iron |
| why should cross connections between storm and sanitary sewers be avoided. | Cross connections should be avoided because such connections can lead to discharge of domestic and industrial waste into lakes and streams. |
| what are the 3 types of sludge | raw sludge, primary sludge, digester sludge |
| Digestion drops volatie solids levels to | Normally, digestion provides 40 – 60 % destruction of the volatile solids but it can be higher |
| what are volatile solids | Those solids in water or other liquids that are lost on ignition of the dry solids at 550� centigrade. |
| what is vaccum filtration | The basic process of filtration is separation of the solids from the liquid by means of a porous media which retains the solids (filter cake) and lets the liquid portion pass through (filtrate) |
| what is covered under the owra section 53 | Primary purpose is to provide a mechanism under which sewage treatment plants can be built and approvals granted |
| Under section 53 of the OWRA | No personal shall establish, extend, or replace etc, without approval granted by director |
| :Plant certification is regulated under what legislation | o reg 129/04 |
| what is a reciprocating pump | Reciprocating pump moves a liquid by a piston that moves back and forth. |
| what are 2 types of positive displacement pumps | Reciprocating pumps: piston and diaphragm pumps Rotary pumps: screw pumps and progressive cavity pumps |
| what are typical uses for pos. disp. pumps | Chemical feed pumps Sampling pumps |
| what is a centrifugal pump | A cent. pump is pump with a rotating impeller throws the water outwards. The water is collected in the casing (volute), and allowed to leave at a single point (pump discharge). A check valve prevents discharge water from flowing back to impeller. |
| what are some types of centrif. pumps | Vertical turbine End suction centrifugal Horizontal split case Submersible Close coupled |
| what is a definition of a confined space | Any space where hazardous gas can accumulate or an oxygen deficient atmosphere can occur |
| define pressure | pressure is the amount of force acting on a certain area |
| what is the conversion factor psi kpa | 6.895 |
| how much heavier than air is chlorine | 2.5 |
| what is a check valve used for | backflow prevention |
| what is a cross connection | Connection between a potable water system and unapproved water supply |
| why is flushing used | to clean lines of impurities or sediment and restore or maintain chlorine residual. |
| what is the mininum system pressure | 140 kpa |
| what is a curb stop | A type of plug valve located one service connection near property line |
| what is a sanitary sewer | a type of underground system for collecting and transporting sewage from houses or industry to treatment or disposal. |
| when does thrust occur | when a sewer is hydraulically overloaded (too much wastewater is trying to flow through a sewer) resulting in sewage backing up in the collection system |
| what is sewer surcharge | when sewer is hydraulically overloaded and |
| what is a sign of sewer surcharge | Signs of this include excessively clear water in the collection system |
Created by:
bfennell