1. Where can you find the g...
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1. Where can you find the groundwater?
Near the surface of the earth、 in the zone of aeration、Gravity water、Capillary water(毛细水), Hygroscopic moisture（潮湿水）, and in the soil pores（空隙）.
2. How many sources of water supply are there in the world? And what are they?
There are two sources of water supply in the world. They are groundwater supplies and surface water supplies.
3. What are the characteristics of water sources?
- It mainly exists at depths less than 600 meters;
- It is more reliable than surface water. It is clearer and contains more mineral substance;
- Its temperature is constant.
- Its quantities often fluctuate（起伏） widely;
- The water quality is affected by pollution sources;
- It contains less mineral substance;
- Its temperature is changeable.
In summary, the distribution of water sources is uneven(不规则的) both in space and time. The fresh water is easily polluted and limited in terms of quantity.
4. Try to describe the wastewater collection system(type and flow).
Wastewater system can be mainly divided into two flow types: combined sewer system and separate sewer system.
The former one means that pollute water would be drained off together with storm water. And the latter one means that the system was separated into pollute sewer and storm sewer.
The advantage of combined sewer is low price, convenience of construction and management. The disadvantage is that if the combined wastewater was rained into natural water body directly, the water body will be polluted seriously. So now we used to construct it into interceptor combined sewer system, when it has no rain, the polluted water will be drained into waster water treatment plant. When it rained for a while, the redundant part of combined wastewater will be drained into water body. It will lessen the extent of pollution.
The advantage of separate sewer system is the construction and implementation can be done by stages. it will also lessen pollution effectively. But the disadvantage is that initial rainfall pollution and higher investment. So we don't often use just one type of system in an area, we should adjust measures to local conditions, considerate environment, technology and also finance, to figure out the optimum wastewater drainage system.
5. What is the definition of Solids? And how to measure them?
Definition: the usual definition of solids is the residue after evaporation at $10^3℃$.
How to measure: the solids measured are known as total Solids. We can measure the total solids by weigh the residue after evaporation at $10^3℃$.
Total solids may be divided into two fractions: the total dissolved solids and the total suspended solids. A filter is used to separate the TSS(Total suspended solids) from the TDS(Total dissolved solids). The solids adhere in the filter paper is the TSS, and the solids contained in the filtrate is the TDS.
6. What is the definition of PH?And how to measure it?
The PH of solution is a measure of hydrogen ion concentration, which is a measure of its acidity. PH is defined as the negative logarithm(负对数) of the hydrogen-ion concentration. The measurement of PH is now almost universally by electronic means.
7. What is the definition of Alkalinity? And how to measure it?
A parameter related to PH is alkalinity, or the buffering capacity of the water against acids. Alkalinity can be defined in terms of molar quantities(物质的量), in terms of calcium carbonate(碳酸钙).
8. What's the definition of DO? And how to measure it?
DO means the amount of oxygen dissovled in solution. DO is usually measured either with an oxygen probe or by iodometric titration(碘量滴定).
9. What is the definition of BOD? And how to measure it?
Definition: BOD is a measure of the amount of oxygen required by bacteria and other microorganisms engaged in stabilizing decomposable organic matter.
How to measure: The most widely used parameter of organic pollution applied to both wastewater and surface water is the 5-day BOD. This determination（测定） involves the measurement of the dissolved oxygen used by microorganisms in the biochemical oxidation of organic matter.
10. What is COD? How to measure it?
COD means chemical oxygen demand(COD), that is the oxygen demand when the organic compounds are oxidized chemically.
The COD test is used to measure the oxygen equivalent of the organic material in wastewater that can he oxidized chemically using dichromate(重铬酸钾) in an acid solution,as illustrated in the following equation, when the organic nitrogen is in the reduced state (oxidation number=-3).
11. What is the definition of Turbidity? And how to measure it?
Turbidity is another test used to indicate the quality of waste discharges and natural waters with respect to colloidal(胶体的) and residual suspended matter. The measurement of turbidity is based on comparison of the intensity of light scattered by a sample to the light scattered by a reference suspension under the conditions.
12. What is the definition of Nitrogen? And how to measure it?
Nitrogen is an essential building block（重要构成要素） in the synthesis of protein. Organic nitrogen is determined analytically using the Kjeldahl method(凯式法). The aqueous（含水的） sample is first boiled to drive off the ammonia（氨水）, and then it is digested（煮解）. During digestion the organic nitrogen is converted to ammonium（铵） through the action of heat and acid. Total kjeldahl nitrogen is determined in the same manner as organic nitrogen, except that the ammonia is not driven off before the digestion step.
13. What is the definition of Phosphates?And how to measure it?
Definition: The usual phophaphorus(磷) that are found in aqueous solutions include the orthphosphate, polyphosphate, and organic phosphate.
Measure: Orthphosphate can be determined by directly adding a substance such as ammonium molybdate, which will form acolored complex with Phosphate. The polyphosphates and organic phosphates must be converted to orthophosphates using acid digestion step before they can be determined in a similar manner.
14. What is the definition of Color? And how to measure it?
Physical parameters of drinking water quality. It can be caused by organic substances such as algae or humic（腐殖的） compounds.
Color is measured by comparison with standards, Colored water made with potassium chloroplatinate（氯铂酸钾） when tinted with cobalt chloride（氯化钴） closely resembles the color of many natural waters.
15. What is the definition of Odor? And how to measure it?
The definition: Odor means the sensation(知觉) that results when olfactory receptors（嗅觉受体） in the nose are stimulated by particular chemicals in gaseous（气体的） form.
The measurement: It can be measured by sensory（感觉的） methods, and specific odorant concentrations can be measured by instrumental methods. The threshold（程度） odor of a water or wastewater sample is determined by diluting（稀释的） the sample with odor-free water（无味水）. The"threshold odor number" (TON)corresponds（一致） to the greatest dilution of the sample with odor-free water at which an odor is just perceptible. The recommended sample size is 200ml. The numerical value of the TON is determined as follow: ON=A+B/A; where TON=threshold odor number A=ML of sample B=ml of odor-free water.
16. What is the definition of Trace toxic organic compounds? And how to measure them?
Trace toxic organic compounds（微毒有机化合物） is what can cause human body poisoning or cause environmental pollution of organic matter. Their concentrations in the water are not high, but the time of the residual in the water is long, so it can accumulate Very low concentrations of chlorinated hydrocarbons and other agrichemical residues in water can be assayed by gas chromatography. Oil residues in water are generally measured by extracting the water sample with Freon and then evaporating the Freon and weighing the residue from this evaporation.
17. How many levels of wastewater treatment? And what are they?
There are seven levels of wastewater treatment:
- Preliminary Removal of wastewater constituents such as rags, sticks; floatables grits and grease that may cause maintenance or operational problems with the treatment operations, processes, and ancillary systems;
- Primary Removal of portion of the suspended solids and organic matter from the wastewater;
- Advanced primary Enhanced removal of suspended solids and organic matter from the wastewater. Typically accomplished, by chemical addition or filtration;
- Secondary Removal of biodegradable organic matter(in solution or in suspension) and suspended solids. Disinfection is also typically included in the definition of conventional secondary treatment;
- Secondary with nutrient removal Removal of biodegradable organics, suspended solids, and nutrients(nitrogen, phosphorus, or both nitrogen and phosphorus;
- Tertiary Removal of residual suspended solids(after secondary treatment), usually by granular medium filtration or microscreens. Disinfection is also typically apart of tertiary treatment, Nutrient removal is often included in this definition;
- Advanced Removal of dissolved and suspended materials remaining after normal biological treatment when required for various water reuse applications.
18. What is the definition of Heavy Metals(重金属)? And how to measure them?
Heavy metals: Metallic elements with high atomic weights (mercury, arsenic, chromium, cadmium, and lead). They can damage living things at low concentrations.
Measurement: Consequently, the method of measuring these ions in water must be very sensitive. The method of choice is atomic absorption spectrophotometry, in which a solution of lanthanum chloride is added to the sample, and the treated sample is sprayed into a flame using an atomizer. Each metallic element in the sample imparts a characteristic
color to the flame, whose intensity is then measured spectrophotometrically.
19. What is the new direction and concerns, future trends of wastewater treatment?
New directions and concerns in wastewater treatment are evident in various specific areas of wastewater treatment. The changing nature of the wastewater to be treated, emerging health and environmental concerns, the problems of industrial wastes, and the impact of new regulations, are among the most important. Further,other important concerns include: (1)aging infrastructure（基础设施老化）; (2)new methods of process analysis and control; (3)treatment plant performance and reliability; (4)wastewater disinfection; (5)combined sewer overflows; (6)impacts of stormwater flows, and sanitary(卫生的) overflows and nonpoint sources of pollution, (7)separate treatment of return flows and (8)odor control and the control of VOC（Volatile organic chemicals） emissions.
It's clear that the future trends in wastewater treatment plant design will be for facilities providing higher levels of treatment. Some of the innovative treatment methods being utilized in new and upgraded treatment facilities include vortex separators(涡流分离器), high rate clarification, membrane bioreactors, pressure-driven membrane filtration (ultrafiltration and reverse osmosis), and ultraviolet radiation (low-pressure, low-and high-intensity UV lamps, and medium-pressure, high-intensity UV lamps). Some of the new technologies are more compact and are particularly well suited for plants where available space for expansion is limited.
20. What is the new directions and concerns, future trends of wastewater reuse.
New Concern: New trace contaminants
A number of communities use water sources that contain a significant
wastewater component. Even though these sources, after treatment, meet current drinking water standards, the growing knowledge of the potential impacts of new trace contaminants raises concern.
① New Technologies
As conventional technologies may be incapable of reducing the levels of trace contaminants below where they are not considered as a potential threat to public health, new technologies that offer improved levels of treatment need to be tested and evaluated.
② Risk Assessment
Where indirect potable reuse is considered, risk assessment becomes an important component of a water reuse investigation.
Future Trends: New Technologies
The future trends of waste water reuse is the development and application of new technologies.
Technologies that are suitable for water reuse application include membranes, carbon adsorption, advanced oxidation, ion exchange, and air stripping .Among them, membranes are most significant developments because of its wide applications and has been considered to be one of the predominant treatment technologies.
21. What is the new directions and concerns, future trends of biosolids management?
Answer: First, special compounds removal; Anaerobic and aerobic digestion; Third: stricter regulation; Trends: high solids centrifuges and heat dryers; Anaerobic and aerobic digestion.
22. Please summarize the role and characteristics of Screening.
Answer: The principal role of screening is to remove coarse materials from the flow stream that could (1) damage subsequent process equipment, (2) reduce overall
treatment process reliability and effectiveness, or (3) contaminate waterways. Fine
screens are sometimes used in place of or following coarse screens where greater
removals of solids are required to (1) protect process equipment or (2) eliminate
materials that may inhibit the beneficial reuse of biosolids.
Characteristics of coarse Screens: coarse screens have clear openings ranging from 6 to 150mm;
Characteristics of fine Screens: fine screens have clear openings less than 501μm are used principally in removing fine solids from treated effluents.
The screening element may consist of parallel bars, rods and wires, grating, wire mesh, or perforated plate, and the opening may be of any shape but generally are circular or rectangular slots.
Answer: Role destabilize colloidal particles so that particle growth can occur as a
result of particle collisions.
- coagulation reactions are often incomplete；
- A coagulant is the chemical that add to destabilize the colloidal particles in wastewater;
- The electrical double layer consists of k compact layer in which the potential drops.
Answer: Role: produce particles by means of aggregation
- A flocculant is a chemical, typically organic, added to enhance the flocculation process;
- There are two types of flocculation: micro flocculation and macro flocculation.
- typical flocculants and coagulants include natural and synthetic organic polymers, metal salts such as alum or ferric sulfate, and prehydrolized metal salts such as polyaluminum chloride (PACI)and polyiron chloride (PICI).
25. Please summarize the role and characteristics of Gravity Separation.
On the basis of the concentration and the tendency of particles to interact, four types of gravitational settling can occur: (1)discrete particle, (2)flocculent, (3)hindered(also called zone), and(4)compression.
Roles: To separate of suspended particles that are heavier than water by gravitational setting.
26. Please summarize the role and characteristics of Anaerobic Treatment.
Role: the purpose of this section is to present process designs for other anaerobic
treatment processes used to remove organic material from liquid streams.
Advantages: energy considerations, lower biomass yield, fewer nutrients required
and higher volumetric loading.
Disadvantages: operational considerations, the need for alkalinity addition, and the need for further treatment are highlighted.
27. Please summarize the role and characteristics of Filtration
Characteristics: It has two types: depth filtration and surface filtration.
The basic of the depth filtration including: (1) the physical features of a conventional granular medium-depth filter; (2) filter-medium characteristic; (3)the filtration process; (4)the operative particle-removal mechanisms; and(5)the backwash process. The surface filtration includes all kinds of membrane filtrations.
The process of rapid sand filtration involves two operations: filtration and Backwashing.
Roles: To remove suspended solids and organic matter.
Depth filtration is now used to achieve supplemental removals of suspended solids from wastewater effluent of biological and chemical treatment process to reduce the mass discharge of solids and, perhaps more importantly, as a conditioning step that will allow for the effective disinfection of the filtered.
Depth filtration is also used as a pretreatment step for membrane filtration. Single and two-stage filtration is also used to remove chemically precipitated phosphorus.
28. Please summarize the role and characteristics of Adsorption.
- (a) Removing a portion of the remaining dissolved organic matter;
- (b) Toxicity reduction.
- Adsorption is the process of accumulating substances that are in solution on a suitable interface;
- Adsorption is a mass transfer operation in that a constituent in the liquid phase is transferred to the solid phase;
- Adsorption is used at the air-liquid interface in the flotation process and the liquid-solid interface in wastewater treatment;
- The principal types of adsorbents include activated carbon, synthetic polymeric and silica-based adsorbers;
- Activated carbon is used most commonly in advanced water-treatment applications.
28. Please summarize the role and characteristics of Chemical Oxidation and Advanced Oxidation Process.
Role & Application:
Generally, Chemical Oxidation and Advanced Oxidation are both unit operations used in wastewater treatment, which can bring about changes in the chemical composition of a compound or a group of compounds
Chemical Oxidatian, in the past, was used commonly to.
- Reduce the concentration of residual organics;
- Control odors;
- Remove ammonia;
- Reduce the bacterial and viral content of wastewater.
Now Chemical Oxidation is commonly used to:
Improve the treatability of non-biodegradable organic compounds;
Eliminate the inhibitory effects of certain organic and inorganic compounds to microbial growth;
Reduce or eliminate the toxicity of certain organic and inorganic compounds to microbial growth and aquatic flora.
Advanced Oxidation Process(AOPS) in which the free hydroxyl radical(羟基)is used to oxidize complex organic constituents found in wastewater that are difficult to arade biologically into simpler and products. Typically, disinfection and oxidation of refractory organic compounds are common applications of AOPS.
Chemical oxidation: (1) involve the use of oxidizing agents such as oxygen, chlorine, ozone, and hydrogen peroxide which is usually termed"simple oxidation". Chemical Oxidation typically (2) consists of two half reactions, and accordingly, a two-electron change. (3)Chemical dosages for the removal of refractory organic compounds cannot be
derived from the chemical stoichiometry
AOPS. typically (1) involve the generation and use of the hydroxyl free
radical(HO )as a strong oxidant to destroy compounds that cannot be oxidized by conventional oxidants such as oxygen, ozone, and chlorine.
Non-selective in their mode of attack and able to operate at normal temperature and pressures, hydroxyl radicals (2)are capable of oxidizing almost all reduced materials present without restriction to specific classes or groups of compounds, as compared to other oxidants.
AOPS differ from the other treatment processes because (3)wastewater compounds are degradable rather than concentrated or transferred into a different phase.
AOPS are (4).usually applied to low COD wastewaters. because of the cost of ozone and/or H202 required to generate the hydroxyl radicals.
29. Please summarize the role and characteristics of ion Exchange.
Role: For Nitrogen Control, ion Exchange is used to remove Nitrogen from the waste stream. Which contain ammonium, NHA, and nitrate, NO3. By ion Exchange, we can control the content of nitrogen and make it be what we want. Removal of Heavy Metals, Because of the potential accumulation and toxicity of these metals It is desirable to remove them from wastewater effluents. before release to the environment. In the ion Exchange, we can use materials which like as zeolites, weak and strong anion and Cation resins, microbial, and plant biomass to swap out heavy
metals, such as Cr. Ni. Cu. Zn. Cd. Pb. Removal of Total Dissolved Solids. The wastewater is first passed through a cation exchange When the positively charged ions are replaced by hydrogen ions. The cation-exchanger Effluent is then passed over an anionic-excharge resin where the anions are replaced by Hydrogen ions. Thus that react to form water molecules.
Characteristics: total materials which participate in ion Exchange must be dissolved, and there must be chemical reactions in the ion Exchange. The processes of ion Exchange are complex, but we are able to gain the accurate consequence because the professional and precise of the complex processes.
30. Please summarize the role and characteristics of Membrane Filtration.
Role: Membrane filtration is a kind of filtration which use membrane as a selective barrier that will allow the passage of certain constituents and will retain other constituents found in the liquid. Membrane filtration is widely used in water treatment.
Summarize the role and characteristics of activated-sludge process?
Role: The activated-sludge process is now used to routinely for biological treatment of municipal and industrial, waste waters. Specifically, the biological treatment is essential for removing soluble, colloidal, and particulate (suspended)organic substances; for biological nitrification and denitrification; and for biological hosphorus remova.
The basic activated-sludge treatment process consists of the following three basic components: (a) A reactor in which the microganisms responsible for treatment are kept suspension and aerated,
(b) Liquid-solids separation, usually in a sedimentation tank, (c) A recycle system for returning solids removed from the liquid-solids separation unit back to the reactor.
The activated-sludge process is the formation of flocculent settleable solids that can be removed by gravity settling in sedimentation tanks
3.operational problems of activated-sludge process are bulking sludge, rising sludge, and Nocardia foam.
Please summarize the role and characteristics of Trickling Filter.
Provide biological wastewater treatment of municipal and industrial wastewater, non submerged fixed-film biological reactor using rock or plastic packing lows over which wastewater is distributed continuously. Rock Filter beds are usually circular, and the liquid wastewater is distributed over the top of the bed by a rotary distributor. plastic packing.
33. Please summarize the role and characteristics of Anaerobic Treatment.
Role: the purpose of this section is to present process designs for other anaerobic treatment processes used to remove organic material from liquid streams.
Advantages: energy considerations, lower biomass yield, fewer nutrients required and higher volumetric loading.
Disadvantages: operational considerations, the need for alkalinity addition, and the need for further treatment are highlighted.
34. Please summarize the role and characteristics of Rotating Biological Contactors.
A rotating biological contactor is a type of secondary (Biological) treatment process. It consists of a series of closely spaced, parallel discs mounted on a rotating shaft which is supported just above the surface of the waste water. Microorganisms grow on the surface of the discs where biological degradation of the wastewater pollutants takes place.
water supply engineering
Screen, Coagulation, Flocculation, Gravity separation, Filtration, Colloid
The typical surface water treatment process.
Main factors that affect the coagulation affect.
The method of disinfection.
The kind of water.
osmosis, reverse osmosis.
BOD, COD, DO, TOC, TOD, Alkalinity, SS, Turbidity, PH, Heavy metals, Primary treatment, Secondary treatment, Tertiary treatment, Activated sludge process, Biofilm process, SBR, Gravity concentration, Sludge, disposal, MBR, A2/O, Wastewater, collection system.
How to remove nitrogen and phosphorus?
Type of stabilization pond.
Different between primary sedimentation tank and secondary sedimentation tank.
The technological process of sewage treatment works.
Different between activated sludge process and biofilm process.
The method of wastewater treatment.
The process of activated sludge process.
The process of sludge treatment.
The process of biological membrane method.
The purpose of sludge treatment.