Environmental Engineering interview questions

1. A.bench-scale trial dosing alum into water samples at varying doses to find the coagulant dose giving the best floc and lowest residual turbidity
2. B.dosing chlorine until all ammonia is oxidised and free residual chlorine begins to appear, marking the dose that gives true disinfection
3. C.oxygen consumed by microbes oxidising biodegradable organics, measured over 5 days at 20 °C or 3 days at 27 °C in Indian practice
4. D.oxygen equivalent of organics oxidised by potassium dichromate in a 2 to 3 hour test, always at least equal to the biological demand

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1. A.Jar test
2. B.Surface overflow rate
3. C.Hardness of water
4. D.Biochemical oxygen demand

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1. A.Biochemical oxygen demand — dosing chlorine until all ammonia is oxidised and free residual chlorine begins to appear, marking the dose that gives true disinfection
2. B.Biochemical oxygen demand — stabilisation of sludge by bacteria without oxygen at about 35 °C for around 30 days, yielding biogas that is 65 to 70 percent methane
3. C.Biochemical oxygen demand — flow divided by tank plan area, the settling velocity that a particle must exceed to be removed, so it governs sedimentation tank sizing
4. D.Biochemical oxygen demand — oxygen consumed by microbes oxidising biodegradable organics, measured over 5 days at 20 °C or 3 days at 27 °C in Indian practice

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1. A.oxygen equivalent of organics oxidised by potassium dichromate in a 2 to 3 hour test, always at least equal to the biological demand
2. B.flow divided by tank plan area, the settling velocity that a particle must exceed to be removed, so it governs sedimentation tank sizing
3. C.oxygen consumed by microbes oxidising biodegradable organics, measured over 5 days at 20 °C or 3 days at 27 °C in Indian practice
4. D.calcium and magnesium salts; carbonate hardness is removed by boiling while non-carbonate hardness needs lime-soda or ion exchange

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1. A.Biochemical oxygen demand
2. B.Chemical oxygen demand
3. C.IS 10500 drinking water limits
4. D.Breakpoint chlorination

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1. A.Chemical oxygen demand — pH 6.5 to 8.5, turbidity 1 NTU acceptable and 5 permissible, TDS 500 acceptable and 2000 permissible, residual chlorine at least 0.2 mg/L
2. B.Chemical oxygen demand — flow divided by tank plan area, the settling velocity that a particle must exceed to be removed, so it governs sedimentation tank sizing
3. C.Chemical oxygen demand — millilitres occupied by one gram of activated sludge after settling 30 minutes; 50 to 150 settles well and above 150 indicates bulking
4. D.Chemical oxygen demand — oxygen equivalent of organics oxidised by potassium dichromate in a 2 to 3 hour test, always at least equal to the biological demand

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1. A.calcium and magnesium salts; carbonate hardness is removed by boiling while non-carbonate hardness needs lime-soda or ion exchange
2. B.stabilisation of sludge by bacteria without oxygen at about 35 °C for around 30 days, yielding biogas that is 65 to 70 percent methane
3. C.millilitres occupied by one gram of activated sludge after settling 30 minutes; 50 to 150 settles well and above 150 indicates bulking
4. D.pH 6.5 to 8.5, turbidity 1 NTU acceptable and 5 permissible, TDS 500 acceptable and 2000 permissible, residual chlorine at least 0.2 mg/L

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1. A.Sludge volume index
2. B.Chemical oxygen demand
3. C.Breakpoint chlorination
4. D.Hardness of water

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1. A.Hardness of water — pH 6.5 to 8.5, turbidity 1 NTU acceptable and 5 permissible, TDS 500 acceptable and 2000 permissible, residual chlorine at least 0.2 mg/L
2. B.Hardness of water — calcium and magnesium salts; carbonate hardness is removed by boiling while non-carbonate hardness needs lime-soda or ion exchange
3. C.Hardness of water — millilitres occupied by one gram of activated sludge after settling 30 minutes; 50 to 150 settles well and above 150 indicates bulking
4. D.Hardness of water — bench-scale trial dosing alum into water samples at varying doses to find the coagulant dose giving the best floc and lowest residual turbidity

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1. A.dosing chlorine until all ammonia is oxidised and free residual chlorine begins to appear, marking the dose that gives true disinfection
2. B.flow divided by tank plan area, the settling velocity that a particle must exceed to be removed, so it governs sedimentation tank sizing
3. C.oxygen consumed by microbes oxidising biodegradable organics, measured over 5 days at 20 °C or 3 days at 27 °C in Indian practice
4. D.pH 6.5 to 8.5, turbidity 1 NTU acceptable and 5 permissible, TDS 500 acceptable and 2000 permissible, residual chlorine at least 0.2 mg/L

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1. A.IS 10500 drinking water limits
2. B.Biochemical oxygen demand
3. C.NAAQS particulate limits
4. D.Jar test

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1. A.IS 10500 drinking water limits — pH 6.5 to 8.5, turbidity 1 NTU acceptable and 5 permissible, TDS 500 acceptable and 2000 permissible, residual chlorine at least 0.2 mg/L
2. B.IS 10500 drinking water limits — flow divided by tank plan area, the settling velocity that a particle must exceed to be removed, so it governs sedimentation tank sizing
3. C.IS 10500 drinking water limits — bench-scale trial dosing alum into water samples at varying doses to find the coagulant dose giving the best floc and lowest residual turbidity
4. D.IS 10500 drinking water limits — 24-hour standards of 60 µg/m³ for PM2.5 and 100 µg/m³ for PM10, with annual limits of 40 and 60 respectively

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1. A.oxygen consumed by microbes oxidising biodegradable organics, measured over 5 days at 20 °C or 3 days at 27 °C in Indian practice
2. B.oxygen equivalent of organics oxidised by potassium dichromate in a 2 to 3 hour test, always at least equal to the biological demand
3. C.stabilisation of sludge by bacteria without oxygen at about 35 °C for around 30 days, yielding biogas that is 65 to 70 percent methane
4. D.24-hour standards of 60 µg/m³ for PM2.5 and 100 µg/m³ for PM10, with annual limits of 40 and 60 respectively

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1. A.Breakpoint chlorination
2. B.Biochemical oxygen demand
3. C.NAAQS particulate limits
4. D.IS 10500 drinking water limits

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1. A.NAAQS particulate limits — flow divided by tank plan area, the settling velocity that a particle must exceed to be removed, so it governs sedimentation tank sizing
2. B.NAAQS particulate limits — oxygen equivalent of organics oxidised by potassium dichromate in a 2 to 3 hour test, always at least equal to the biological demand
3. C.NAAQS particulate limits — millilitres occupied by one gram of activated sludge after settling 30 minutes; 50 to 150 settles well and above 150 indicates bulking
4. D.NAAQS particulate limits — 24-hour standards of 60 µg/m³ for PM2.5 and 100 µg/m³ for PM10, with annual limits of 40 and 60 respectively

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1. A.bench-scale trial dosing alum into water samples at varying doses to find the coagulant dose giving the best floc and lowest residual turbidity
2. B.pH 6.5 to 8.5, turbidity 1 NTU acceptable and 5 permissible, TDS 500 acceptable and 2000 permissible, residual chlorine at least 0.2 mg/L
3. C.24-hour standards of 60 µg/m³ for PM2.5 and 100 µg/m³ for PM10, with annual limits of 40 and 60 respectively
4. D.dosing chlorine until all ammonia is oxidised and free residual chlorine begins to appear, marking the dose that gives true disinfection

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1. A.Surface overflow rate
2. B.Anaerobic sludge digestion
3. C.Hardness of water
4. D.Jar test

Answer + AI explanation with Pro

1. A.Jar test — calcium and magnesium salts; carbonate hardness is removed by boiling while non-carbonate hardness needs lime-soda or ion exchange
2. B.Jar test — bench-scale trial dosing alum into water samples at varying doses to find the coagulant dose giving the best floc and lowest residual turbidity
3. C.Jar test — stabilisation of sludge by bacteria without oxygen at about 35 °C for around 30 days, yielding biogas that is 65 to 70 percent methane
4. D.Jar test — 24-hour standards of 60 µg/m³ for PM2.5 and 100 µg/m³ for PM10, with annual limits of 40 and 60 respectively

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1. A.oxygen equivalent of organics oxidised by potassium dichromate in a 2 to 3 hour test, always at least equal to the biological demand
2. B.oxygen consumed by microbes oxidising biodegradable organics, measured over 5 days at 20 °C or 3 days at 27 °C in Indian practice
3. C.pH 6.5 to 8.5, turbidity 1 NTU acceptable and 5 permissible, TDS 500 acceptable and 2000 permissible, residual chlorine at least 0.2 mg/L
4. D.dosing chlorine until all ammonia is oxidised and free residual chlorine begins to appear, marking the dose that gives true disinfection

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1. A.Anaerobic sludge digestion
2. B.Hardness of water
3. C.Breakpoint chlorination
4. D.Sludge volume index

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1. A.Breakpoint chlorination — oxygen equivalent of organics oxidised by potassium dichromate in a 2 to 3 hour test, always at least equal to the biological demand
2. B.Breakpoint chlorination — dosing chlorine until all ammonia is oxidised and free residual chlorine begins to appear, marking the dose that gives true disinfection
3. C.Breakpoint chlorination — flow divided by tank plan area, the settling velocity that a particle must exceed to be removed, so it governs sedimentation tank sizing
4. D.Breakpoint chlorination — pH 6.5 to 8.5, turbidity 1 NTU acceptable and 5 permissible, TDS 500 acceptable and 2000 permissible, residual chlorine at least 0.2 mg/L

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1. A.dosing chlorine until all ammonia is oxidised and free residual chlorine begins to appear, marking the dose that gives true disinfection
2. B.millilitres occupied by one gram of activated sludge after settling 30 minutes; 50 to 150 settles well and above 150 indicates bulking
3. C.pH 6.5 to 8.5, turbidity 1 NTU acceptable and 5 permissible, TDS 500 acceptable and 2000 permissible, residual chlorine at least 0.2 mg/L
4. D.bench-scale trial dosing alum into water samples at varying doses to find the coagulant dose giving the best floc and lowest residual turbidity

Answer + AI explanation with Pro

1. A.Chemical oxygen demand
2. B.Sludge volume index
3. C.Surface overflow rate
4. D.Biochemical oxygen demand

Answer + AI explanation with Pro

1. A.Sludge volume index — pH 6.5 to 8.5, turbidity 1 NTU acceptable and 5 permissible, TDS 500 acceptable and 2000 permissible, residual chlorine at least 0.2 mg/L
2. B.Sludge volume index — calcium and magnesium salts; carbonate hardness is removed by boiling while non-carbonate hardness needs lime-soda or ion exchange
3. C.Sludge volume index — stabilisation of sludge by bacteria without oxygen at about 35 °C for around 30 days, yielding biogas that is 65 to 70 percent methane
4. D.Sludge volume index — millilitres occupied by one gram of activated sludge after settling 30 minutes; 50 to 150 settles well and above 150 indicates bulking

Answer + AI explanation with Pro

1. A.pH 6.5 to 8.5, turbidity 1 NTU acceptable and 5 permissible, TDS 500 acceptable and 2000 permissible, residual chlorine at least 0.2 mg/L
2. B.oxygen equivalent of organics oxidised by potassium dichromate in a 2 to 3 hour test, always at least equal to the biological demand
3. C.dosing chlorine until all ammonia is oxidised and free residual chlorine begins to appear, marking the dose that gives true disinfection
4. D.flow divided by tank plan area, the settling velocity that a particle must exceed to be removed, so it governs sedimentation tank sizing

Answer + AI explanation with Pro

1. A.Surface overflow rate
2. B.Biochemical oxygen demand
3. C.Jar test
4. D.Hardness of water

Answer + AI explanation with Pro

1. A.Surface overflow rate — calcium and magnesium salts; carbonate hardness is removed by boiling while non-carbonate hardness needs lime-soda or ion exchange
2. B.Surface overflow rate — stabilisation of sludge by bacteria without oxygen at about 35 °C for around 30 days, yielding biogas that is 65 to 70 percent methane
3. C.Surface overflow rate — flow divided by tank plan area, the settling velocity that a particle must exceed to be removed, so it governs sedimentation tank sizing
4. D.Surface overflow rate — bench-scale trial dosing alum into water samples at varying doses to find the coagulant dose giving the best floc and lowest residual turbidity

Answer + AI explanation with Pro

1. A.pH 6.5 to 8.5, turbidity 1 NTU acceptable and 5 permissible, TDS 500 acceptable and 2000 permissible, residual chlorine at least 0.2 mg/L
2. B.flow divided by tank plan area, the settling velocity that a particle must exceed to be removed, so it governs sedimentation tank sizing
3. C.oxygen equivalent of organics oxidised by potassium dichromate in a 2 to 3 hour test, always at least equal to the biological demand
4. D.stabilisation of sludge by bacteria without oxygen at about 35 °C for around 30 days, yielding biogas that is 65 to 70 percent methane

Answer + AI explanation with Pro

1. A.Surface overflow rate
2. B.Anaerobic sludge digestion
3. C.Breakpoint chlorination
4. D.Hardness of water

Answer + AI explanation with Pro

1. A.Anaerobic sludge digestion — calcium and magnesium salts; carbonate hardness is removed by boiling while non-carbonate hardness needs lime-soda or ion exchange
2. B.Anaerobic sludge digestion — bench-scale trial dosing alum into water samples at varying doses to find the coagulant dose giving the best floc and lowest residual turbidity
3. C.Anaerobic sludge digestion — millilitres occupied by one gram of activated sludge after settling 30 minutes; 50 to 150 settles well and above 150 indicates bulking
4. D.Anaerobic sludge digestion — stabilisation of sludge by bacteria without oxygen at about 35 °C for around 30 days, yielding biogas that is 65 to 70 percent methane

Answer + AI explanation with Pro