Instruction
- Total number of questions : 17
- Time allotted : 25:30 Minutes:Seconds.
- Each question carry 1 mark, no negative marks.
- DO NOT refresh the page.
- All the best
Environmental Engineering [ Question No: 1 To 17 ] :
Bleaching powder used in water purification has the chemical formula as :
The process used in domestic water softening, where sodium ion form a cationic exchange resin replace the calcium & magnesium ion reducing the hardness of water is done by :
Three basic processes are involved in the overall anaerobic digestion of sewage sludge following any of the sequence :
Which indicator bacteria indicates recent fecal contamination of water and detected in glucose azide broth ?
In which zone of pollution in river stream, the presence of dissolved oxygen will be minimum?
For maximum discharge in an egg shaped sewer, the ratio of depth of flow to vertical diameter is:-
Which biological wastewater treatment system consists of large diameter corrugated plastic media centered on a horizontal shaft and submerged 40% in wastewater ?
In a pre-treatment for sewage treatment plants following are removed :
The sewage treatment plant which part require large area :-
Laboratory, Testing of Biological Oxygen Demand (BOD) is done by using :
COD test in a measure of the oxygen equivalent of organic matter in wastewater that can be oxidized by :
In wastewater treatment................... is the odor formation and causes impact on treatment process.
A stream having flow of 30m3/s and BOD concentration of 10mg/L receives industrial waste water having flow of 5m3/s and BOD concentration of 120mg/L. The BOD concentration (mg/L) of stream at downward point of meeting of stream with industrial waste is:-
A sample of water has calcium content of 60 mg/l as CaCO\(_3\) and magnesium content of 80 mg/l as CaCO\(_3\). What is the total hardness of water?
On which of the following factors does the dosage of coagulants that should be added to the water NOT depend?
Which of the following is NOT a secondary air pollutant?
Which of the following types of sewers uses pipes that are manufactured by the hot process using clays and shales of special qualities and grades?
Total number of questions : 17
Number of answered questions : 0
Number of unanswered questions : 17
Environmental Engineering [ Question No: 1 To 17 ] :
Bleaching powder used in water purification has the chemical formula as :
Your Answer : (Not Answered)
Correct Answer : C
Bleaching powder is CaOCl\(_{2}\).
Bleaching powder, or chlorinated lime, is made by passing chlorine over slaked lime and is written CaOCl2 (more precisely Ca(OCl)Cl). In water it releases hypochlorous acid and hypochlorite, the 'available chlorine' that disinfects drinking water; good samples hold about 30 to 35 per cent.
CaCl2 is calcium chloride, a drying agent with no disinfecting chlorine. NH4OH is ammonia solution and NH4Cl is ammonium chloride (sal ammoniac); neither is bleaching powder.
The process used in domestic water softening, where sodium ion form a cationic exchange resin replace the calcium & magnesium ion reducing the hardness of water is done by :
Your Answer : (Not Answered)
Correct Answer : A
The process is ion-exchange.
In a domestic water softener, hard water passes through a cation exchange resin charged with sodium ions. The resin takes up the calcium and magnesium ions that cause hardness and releases sodium in their place:
\[ \mathrm{2R{-}Na + Ca^{2+} \rightarrow R_{2}Ca + 2Na^{+}} \]
When the resin is exhausted it is regenerated with brine. Sand filtration and sedimentation remove suspended solids, not dissolved ions, and chlorination disinfects the water; none of them reduces hardness.
Three basic processes are involved in the overall anaerobic digestion of sewage sludge following any of the sequence :
Your Answer : (Not Answered)
Correct Answer : A
The sequence is Hydrolysis → Fermentation → Methanogenesis.
Anaerobic digestion of sludge begins with hydrolysis, in which enzymes break proteins, fats and carbohydrates into soluble molecules. In fermentation (acidogenesis and acetogenesis), bacteria turn these into volatile fatty acids, acetate, hydrogen and carbon dioxide. Finally, in methanogenesis, archaea convert acetate, or hydrogen and carbon dioxide, into methane.
Each step depends on the product of the step before, so the order cannot change. Fermentation cannot precede hydrolysis, since the polymers must first be broken down, and methanogenesis, which needs the products of fermentation, must come last.
Which indicator bacteria indicates recent fecal contamination of water and detected in glucose azide broth ?
Your Answer : (Not Answered)
Correct Answer : B
The indicator is Streptococcus faecalis.
Faecal streptococci (now Enterococcus faecalis and relatives) live in the intestines of humans and warm-blooded animals and do not multiply in water, so their presence points to recent faecal contamination. They are detected in glucose (dextrose) azide broth: sodium azide suppresses gram-negative bacteria, while the streptococci grow and produce acid from glucose.
E. coli is also a faecal indicator, but it is gram-negative and so inhibited by azide. Clostridium perfringens forms spores that persist for long periods and indicates remote rather than recent pollution. Listeria monocytogenes is a pathogen, not a faecal indicator.
In which zone of pollution in river stream, the presence of dissolved oxygen will be minimum?
Your Answer : (Not Answered)
Correct Answer : B
Dissolved oxygen is lowest in the Zone of active decomposition.
Below a sewage outfall a river passes through four zones. In the zone of degradation, DO starts to fall as decomposition begins. In the zone of active decomposition, bacterial action is most intense and DO falls to its minimum, often near zero, with anaerobic conditions and foul gases.
In the zone of recovery reaeration exceeds oxygen demand and DO rises again, and in the zone of clear water conditions return to normal.
For maximum discharge in an egg shaped sewer, the ratio of depth of flow to vertical diameter is:-
Your Answer : (Not Answered)
Correct Answer : A
The key gives a depth ratio of 0.95.
In a closed conduit that narrows towards the top, the discharge is greatest just before it runs full. Near the crown, a small rise in depth adds little flow area but a lot of wetted perimeter (the conduit's top), so the hydraulic radius, and with it the velocity, falls. The discharge therefore peaks at a depth slightly below full, of the order of 0.95 of the vertical diameter, as in a circular sewer.
A full sewer (1.0) carries a little less than this maximum for that reason, and depths of 0.33 or 0.5 are far below the peak.
Which biological wastewater treatment system consists of large diameter corrugated plastic media centered on a horizontal shaft and submerged 40% in wastewater ?
Your Answer : (Not Answered)
Correct Answer : C
The system is the rotating biological contactor (printed 'contractors').
A rotating biological contactor consists of closely spaced discs of corrugated plastic, often 2 to 4 metres in diameter, mounted on a horizontal shaft and about 40 per cent submerged in the wastewater. As the shaft turns slowly, the biofilm on the discs is dipped in the wastewater to take up organic matter and then lifted into the air to take up oxygen.
A trickling filter is a fixed bed over which wastewater is sprayed, a sequencing batch reactor is a suspended-growth activated sludge system run in batches, and an in-vessel submerged system has its media fully immersed, not on a rotating shaft.
In a pre-treatment for sewage treatment plants following are removed :
Your Answer : (Not Answered)
Correct Answer : B
Pre-treatment removes grit and large suspended material.
The preliminary stage of a sewage treatment plant protects the pumps and later units. Bar screens remove large floating and suspended objects such as rags, plastics and wood, and grit chambers remove sand, gravel and other heavy inorganic particles that would abrade equipment and settle in tanks.
Large suspended material alone leaves out grit removal, which is the other essential preliminary unit. Settleable (printed 'Settlable') organic solids are removed in the primary sedimentation tank, the next stage. Oil and grease call for skimming tanks, which only some plants provide, so they are not the standard content of pre-treatment.
The sewage treatment plant which part require large area :-
Your Answer : (Not Answered)
Correct Answer : C
The unit that needs a large area is the Oxidation pond.
An oxidation (stabilisation) pond treats sewage in a shallow open basin, typically 1 to 1.5 m deep, where algae supply oxygen through photosynthesis and bacteria break down the organic matter. Because it depends on sunlight and a long detention time, it needs a large land area, which is why it suits small towns where land is cheap.
Biological (trickling) filters and septic tanks are compact units that treat sewage in a much smaller footprint.
Laboratory, Testing of Biological Oxygen Demand (BOD) is done by using :
Your Answer : (Not Answered)
Correct Answer : B
BOD is tested in the laboratory using an incubator.
The biochemical oxygen demand test measures the oxygen consumed by microbes while they break down organic matter. Diluted samples are kept in sealed bottles in a BOD incubator at a fixed temperature, 27 °C for 3 days in the Indian standard or 20 °C for 5 days, and the dissolved oxygen is measured before and after.
An atomic absorption spectrophotometer measures metals, a gas chromatograph separates volatile organic compounds, and a mass spectrometer identifies compounds by their mass. None of them measures biological oxygen uptake.
COD test in a measure of the oxygen equivalent of organic matter in wastewater that can be oxidized by :
Your Answer : (Not Answered)
Correct Answer : A
COD measures the organic matter that can be oxidized by dichromate in an acid solution.
In the chemical oxygen demand test the sample is refluxed with potassium dichromate in strong sulphuric acid, with silver sulphate as catalyst, for about two hours. The dichromate consumed is found by titrating the excess with ferrous ammonium sulphate and expressed as the equivalent oxygen in mg/l. Being chemical, the test oxidizes nearly all organic matter, biodegradable or not, and gives a result in hours.
The three incubation options describe the biochemical oxygen demand test, which measures only what microbes can oxidize: 3 days at 27 °C in the Indian standard, 5 days at 20 °C in the classic method, with seeded microbes where the sample lacks them.
In wastewater treatment................... is the odor formation and causes impact on treatment process.
Your Answer : (Not Answered)
Correct Answer : A
The answer is Sulfate.
Where wastewater turns anaerobic, in long sewers, sludge tanks or digesters, sulfate-reducing bacteria use sulfate as their electron acceptor and reduce it to hydrogen sulfide. H2S gives the rotten-egg odour, corrodes concrete and metal, and is toxic to workers and to the microbes of the treatment process itself.
Chlorine is used to control odour, not a source of it. Alkalinity (printed 'Akalinity') buffers the pH that biological treatment needs. Nitrate is if anything dosed to suppress sulfide formation, because bacteria use it in preference to sulfate.
A stream having flow of 30m3/s and BOD concentration of 10mg/L receives industrial waste water having flow of 5m3/s and BOD concentration of 120mg/L. The BOD concentration (mg/L) of stream at downward point of meeting of stream with industrial waste is:-
Your Answer : (Not Answered)
Correct Answer : B
The BOD downstream is 25.71 mg/L.
After complete mixing, the BOD of the mixture is the flow-weighted average of the two streams.
\[ \begin{aligned} C &= \frac{30 \times 10 + 5 \times 120}{30 + 5} \\ &= \frac{300 + 600}{35} \approx 25.71\ \text{mg/L} \end{aligned} \]
120 mg/L is the waste's own BOD, ignoring dilution. 600 is the BOD load of the waste (flow times concentration), not a concentration. 30 mg/L does not follow from any weighting of the data.
A sample of water has calcium content of 60 mg/l as CaCO\(_3\) and magnesium content of 80 mg/l as CaCO\(_3\). What is the total hardness of water?
Your Answer : (Not Answered)
Correct Answer : B
The total hardness of water is the sum of the calcium hardness and the magnesium hardness, both expressed as CaCO\(_3\):
\[ \begin{aligned} \text{Total hardness} = 60 + 80 \\ &= 140\ \text{mg/l as CaCO}_3 \end{aligned} \]The value 40 mg/l is the difference between the two, 200 mg/l is a sum with a wrong value for one of them, and 240 mg/l would result from adding an extra 100 mg/l. Since the data are already in CaCO\(_3\) equivalents, no conversion factor is needed.
On which of the following factors does the dosage of coagulants that should be added to the water NOT depend?
Your Answer : (Not Answered)
Correct Answer : D
The coagulant dose depends on the turbidity of the water (more suspended matter needs more coagulant), on its temperature (low temperature slows the reactions and flocculation and so needs a larger dose), and on the time available for settlement and the type of coagulant. The question asks for the one on which it does not depend, and the key says it is the viscosity of the water. The viscosity is itself a function of temperature, so it is not treated as a separate factor.
Which of the following is NOT a secondary air pollutant?
Your Answer : (Not Answered)
Correct Answer : D
Nitrogen oxide is not a secondary pollutant. It is a primary pollutant, released directly from combustion in vehicles, furnaces and power plants. Secondary pollutants are not emitted directly but are formed in the air by reactions of primary ones: ozone forms from nitrogen oxides and hydrocarbons in sunlight, formaldehyde forms in the photochemical oxidation of hydrocarbons, and sulphuric acid forms when sulphur dioxide is oxidised and combines with water vapour.
Which of the following types of sewers uses pipes that are manufactured by the hot process using clays and shales of special qualities and grades?
Your Answer : (Not Answered)
Correct Answer : A
Stoneware sewer pipes are made by firing selected clays and shales of special quality in a kiln, the hot process, and are glazed to give a smooth, impervious and corrosion-resistant surface. Brick sewers are built in place from bricks and mortar, plastic sewers are made from PVC or HDPE by extrusion, and asbestos cement sewers are made by mixing asbestos fibre and cement, so none of those is made from clay and shale in a kiln.
Marks
Total number of questions : 17
Number of answered questions : 0
Number of unanswered questions : 17