Description : Pick up the correct statement from the following: A. Hydrogen sulphide gas in excess, may cause corrosion of concrete sewers B. 4 ppm of Dissolved Oxygen (D.O.) is ensured before discharging the treated ... river C. Solubility of oxygen in sewage is 95% of that of distilled water D. All the above
Last Answer : ANS: D
Description : Pick up the correct statement from the following: A. In treated sewage, 4 ppm of D.O. is essential B. Only very fresh sewage contains some dissolved oxygen C. The solubility of oxygen in sewage is 95% that is in distilled water D. All the above
Description : The factor responsible for purification of sewage in river is A. Hydrology B. Dissolved oxygen in water C. Temperature D. All the above
Description : If the depletion of oxygen is found to be 5 ppm after incubating a 2.5% solution of sewage sample for 5 days at 21°C, B.O.D. of the sewage is A. 50 ppm B. 100 ppm C. 150 ppm D. 200 ppm
Description : If 2% solution of a sewage sample is incubated for 5 days at 20°C and depletion of oxygen was found to be 5 ppm, B.O.D. of the sewage is A. 200 ppm B. 225 ppm C. 250 ppm D. None of these
Last Answer : ANS: C
Description : If a 2% solution of sewage sample is incubated for 5 days at 20°C and the dissolved oxygen depletion was found to be 8 mg/l. The BOD of the sewage is A. 100 mg/l B. 200 mg/l C. 300 mg/l D. 400 mg/l
Description : The amount of oxygen consumed by the aerobic bacterias which cause the aerobic biological decomposition of sewage, is known A. Bio-Chemical Oxygen Demand (B.O.D.) B. Dissolved Oxygen (D.O.) C. Chemical Oxygen Demand (C.O.D.) D. None of these
Last Answer : ANS: B
Description : Dilution method of disposing of sewage, is not preferred to A. When sewage is fresh B. When diluting water has high dissolved oxygen content C. When diluting water is used for water supply near the point of sewage disposed D. When the diluting water is having flow currents
Description : Dissolved oxygen content in river water is around __________ ppm. (A) 5 (B) 100 (C) 250 (D) 500
Last Answer : (A) 5
Description : On increasing the temperature the solubility of most of the gases in water decreases. An important consequence of this effect is the thermal pollution of water, such as occurs around power plants cooled by a river or stream. How is the survival of fish affected by thermal pollution of water?
Last Answer : Ans.: When the water temperature of the river or stream is increases the solubility of oxygen in water decreases. Due to this decrease in dissolved oxygen the survival of fish becomes difficult.
Description : As compared to fresh river water, sea water contains oxygen A. 10% less B. 20% less C. 10% more D. 20% more
Description : Imhoff cone is used to determine A. Settleable solids B. Suspended solids C. Dissolved solids D. None of these
Last Answer : ANS: A
Description : The effluent of a septic tank is A. Fit for discharge into any open drain B. Foul and contains dissolved and suspended solids C. As good as that from a complete treatment D. None of these
Description : For existence of aquatic life in water, the dissolved oxygen content in it, should not be less than __________ ppm. (A) 10000 (B) 5 (C) 500 (D) 1000
Last Answer : (B) 5
Description : The optimum dissolved oxygen level (in mg/litre) required for survival of aquatic organisms is - (1) 4 - 6 (2) 2 - 4 (3) 8 - 10 (4) 12 - 16
Last Answer : (1) 4 - 6 Explanation: Oxygen is one of several dissolved gases important to aquatic systems. Dissolved oxygen is necessary to maintain aerobic conditions in surface waters and is ... approach saturation - that concentration which is in equilibrium with the partial pressure of atmospheric oxygen.
Description : The optimum dissolved oxygen level (in mg/litre) required for survival of aquatic organisms is : (1) 4 – 6 (2) 2 – 4 (3) 8 – 10 (4) 12 – 16
Last Answer : 4 – 6
Description : Assertion A. : Discharging the effluents from the oxidation ponds just up stream of lakes or reservoirs is undesirable. Reason (R) : The discharged algae get settled in the reservoirs and cause anaerobic decomposition and other ... of A C. A is true but R is false D. A is false but R is true
Description : Sewer pipes are designed for maximum discharge with 25% to 33% vacant cross-sectional area for A. Unexpected large scale infiltration of stream water B. Unexpected increase in the population C. Under estimates of maximum and average flows D. All of the above
Description : The minimum diameter of sewer to be adopted is A. 10 cm B. 12.5 cm C. 15 cm D. 25 cm
Description : The minimum recommended diameter of sewers, is A. 5 cm B. 10 cm C. 15 cm D. 20 cm
Description : For house drainage minimum gradient is A. 1 in 60 B. 1 in 80 C. 1 in 10 D. 1 in 400
Description : The minimum diameter of a sewer is kept A. 10 cm B. 15 cm C. 20 cm D. 25 cm
Description : The Brake Horse power of the motor (efficiency 60%) required for a pump of capacity 0.075 cumec for a total lift of 12 m, is A. 10 B. 15 C. 20 D. 25 Q No: 44 Aerobic bacterias A. ... presence of free oxygen B. Consume organic matter as their food C. Oxidise organic matter in sewage D. All the above
Description : What take oxygen during the lung respiration and oxygen gas is dissolved in the blood stream?
Last Answer : What is the answer ?
Description : Replenishment of dissolved oxygen in water stream polluted with industrial waste occurs by (A) Natural aeration of water stream (B) Photosynthetic action of algae (C) Both (A) & (B) (D) Neither (A) nor (B)
Last Answer : (C) Both (A) & (B)
Description : Presence of non-biodegradable substances, like alkyl benzene sulphonate (ABS) from the detergents in polluted water stream causes (A) Fire hazards (B) Explosion hazards (C) Persistent foam (D) Depletion of dissolved oxygen
Last Answer : (C) Persistent foam
Description : A sewer pipe contains 1 mm sand particles of specific gravity 2.65 and 5 mm organic particles of specific gravity 1.2, the minimum velocity required for removing the sewerage, is A. 0.30 m/sec B. 0.35 m/sec C. 0.40 m/sec D. 0.45 m/sec
Description : Which one of the following statements regarding septic tanks is wrong? A. A gap of 7.5 cm between the bottom of the covering slab and the top level of scum is provided B. The outlet invert level is kept ... . The minimum width of septic level is 90 cm D. The depth of tank is kept equal to its width
Description : If the depletion of oxygen is found to be 2.5 mg/litre after incubating 2.5 ml of sewage diluted to 250 ml for 5 days at 20°C, B.O.D. of the sewage is A. 50 mg/l B. 100 mg/l C. 150 mg/l D. 250 mg/l
Description : 5 days-biochemical oxygen demand (BOD5) is taken at a temperature of A. 0°C B. 15°C C. 20°C D. 25°C
Description : If the flame of a miner’s safety lamp in a manhole extinguishes within 5 minutes, the sewer certainly contains A. Hydrogen sulphide B. Carbon dioxide C. Methane D. Oxygen
Description : Sewer pipes need be checked for A. Minimum flow B. Maximum flow C. Both A. and B. D. None of these
Description : The ratio of minimum hourly flow to the average flow of sewage is A. 1/4 B. 1/3 C. 1/2 D. 3/4
Description : Assertion A.: The minimum self cleansing velocity in the sewer, at least once a day, must be generated. Reason (R): If certain deposition takes place and is not removed, it obstructs free flow and causes further ... correct explanation of A C. A is true but R is false D. A is false but R is true
Description : Which one of the following part of human body withstands minimum radiation? A. Thyroid B. Kidneys C. Eyes D. Ovaries/testis
Description : Pick up the correct statement from the following: A. Maximum daily flow = 2 times the average daily flow B. Maximum daily flow = average daily flow C. Sewers are designed for minimum permissible velocity at minimum flow D. All the above
Description : Pick up the correct statement from the following: A. The sewer pipes of sizes less than 0.4 m diameter are designed as running full at maximum discharge B. The sewer pipes of sizes greater than 0.4 m ... discharge C. The minimum design velocity of sewer pipes is taken as 0.8 m/sec D. All the above
Description : For efficient working of a sewer, it must be ensured that A. Minimum velocity of 0.45 m/sec, is maintained at its minimum flow B. A maximum velocity of 0.90 m/sec, is maintained at its maximum flow C. Both A. and B. D. Neither A. nor B.
Description : To test chemical oxygen demand (C.O.D.) of sewage, organic matter is oxidised by potassium dichromate in the presence of A. Hydrochloric acid B. Sulphuric acid C. Nitric acid D. Citric acid
Description : If a paper moistened with lead acetate for five minutes when placed in manhole turns black. The sewer certainly contains A. Hydrogen sulphide B. Carbon dioxide C. Methane D. Oxygen
Description : Facultative bacteria survive in A. The presence of oxygen B. The absence of oxygen C. Both cases A. and B. D. Neither A. nor B.
Description : Which one of the following gases is most significant as air pollutant? A. Carbondioxide B. Oxygen C. Nitrogen D. Sulphur-dioxide
Description : Bio-chemical oxygen demand (BOD) for the first 20 days in generally referred to A. Initial demand B. First stage demand C. Carbonaceous demand D. All of these
Description : In a sludge tank, the gas mainly produced, is A. Oxygen B. Nitrogen C. Hydrogen D. Carbon dioxide
Description : Pick up the correct statement from the following: A. Anaerobic bacteria flourish in the absence of oxygen B. Aerobic bacteria flourish in the presence of oxygen C. Facultative bacteria flourish with or without oxygen D. All the above
Description : If the flame of a miner’s safety lamp in the upper layers of the sewer forms an explosive, the sewer certainly contains A. Hydrogen sulphide B. Carbon dioxide C. Methane D. Oxygen
Description : In 1000 kg of sewage, the total solids approximate A. 0.5 to 1.0 kg B. 1 kg to 2.0 kg C. 5 kg to 7.5 kg D. 7.5 kg to 10 kg
Description : In R.C. sewer pipes, the percentage longitudinal reinforcement to the cross-sectional area of concrete is kept A. 10.0 B. 5.0 C. 2.0 D. 0.25
Description : The design period of sewage treatment works in normally A. 5 – 10 years B. 15 – 20 years C. 30 – 40 years D. 40 – 50 years
Description : In a city the ratio of the drainage to sewage is 20, the percentage discharge passing through non-monsoon periods, is A. 5 B. 10 C. 15 D. 20