Hazardous Waste Management Questions and Answers

Answer: B

Schedule II gives the list of waste constituents with concentration limits.

Under the Hazardous and Other Wastes (Management and Transboundary Movement) Rules, 2016, a waste is hazardous if it comes from a process listed in Schedule I, or if it contains any constituent listed in Schedule II above the concentration limit given there. Schedule II is therefore the concentration-limit test.

Schedule I is the list of processes generating hazardous waste. Schedule III lists the hazardous wastes applicable for import and export, in two parts: those requiring prior informed consent and those not requiring it. So the options about processes and about import and export describe the other schedules.

Answer: D

The correct matching is a-iii, b-iv, c-ii, d-i.

• (a) Reacts vigorously with water: phosphorus pentoxide, which reacts violently and exothermically with water to give phosphoric acid; it is a powerful dehydrating agent.
• (b) Reacts spontaneously with air: trimethylaluminium, which is pyrophoric and ignites on contact with air.
• (c) Generates toxic fumes: aluminium nitrate, which gives off toxic nitrogen oxides when heated or in a fire.
• (d) Explosive substance: dynamite.

Option B puts trimethylaluminium against water and phosphorus pentoxide against air; trimethylaluminium does react with water too, but its defining hazard is ignition in air, and phosphorus pentoxide is not air-reactive. Options A and C pair dynamite with air or water reactivity, which misplaces the one explosive.

Answer: B

The match is a-iv, b-iii, c-ii, d-i.

• Ignitable: white phosphorus, which catches fire spontaneously in air.
• Corrosive: sulphuric acid, which destroys tissue and metal.
• Carcinogenic: polyaromatic hydrocarbons, such as benzo(a)pyrene, known to cause cancer.
• Toxic: lead salts, which poison the nervous system and blood.

Sulphuric acid is the clear corrosive, and only option B pairs corrosive with it (b-iii). Options A and D call white phosphorus corrosive, and option C pairs ignitable with lead salts.

Answer: A

The annual return is submitted in Form 4.

Under the Hazardous and Other Wastes (Management and Transboundary Movement) Rules, 2016, every occupier and operator of a disposal facility must keep records of the hazardous waste it handles and file an annual return in Form 4 with the State Pollution Control Board, by 30 June each year for the previous financial year.

Forms 5, 6 and 10 are other forms under the same rules, used for other filings such as the transport manifest, not for the annual return. The annual return lets the Board track how much waste each unit generated, stored, recycled and sent for disposal during the year.

Answer: A

The correct matching is (a)-(3), (b)-(4), (c)-(2), (d)-(1).

• Sulphuric acid is the classic strong acid: (a)-(3).
• Potassium hydroxide (caustic potash) is a strong alkali: (b)-(4).
• Oxygen difluoride, OF₂, is a powerful oxidising and fluorinating agent: (c)-(2).
• Bromine trifluoride, BrF₃, reacts violently with water and is placed among the strong dehydrating agents in this classification: (d)-(1).

The first two pairs settle the answer, since only one code puts sulphuric acid with the acids and potassium hydroxide with the alkalis. The other codes call sulphuric acid an oxidant or an alkali, or match potassium hydroxide with dehydrating agents.

Answer: B

The chemical was vinyl benzene, better known as styrene.

On 7 May 2020, styrene vapour leaked from a storage tank at the LG Polymers plant near Visakhapatnam, Andhra Pradesh, killing several people and affecting thousands in nearby villages. Styrene had polymerised and heated up in a tank left unattended during the COVID-19 lockdown.

Methyl isocyanate was the gas of the Bhopal disaster of 1984. Dichloroethane and trinitrobenzene were not involved.

Answer: C

The key gives cooling failure.

On 11 March 2011 a magnitude 9.0 earthquake shut down the reactors at Fukushima Daiichi, and the tsunami that followed flooded the emergency diesel generators. With all power lost, the cooling systems failed, the reactor cores overheated and three of them melted down, releasing radioactivity. The nuclear disaster itself was the result of the loss of cooling.

The earthquake and tsunami were the natural events that triggered it, so they are causes one step removed. Heavy rain played no part.

Answer: A

The guidelines were issued by the Central Pollution Control Board of India.

The CPCB, the statutory body set up under the Water Act, 1974, has published criteria and guidelines for the siting, design and construction of secure landfills for hazardous waste, including liners, leachate collection and monitoring, under the Hazardous Waste Management Rules.

The other three bodies do not exist. India has a Central Pollution Control Board and State Pollution Control Boards (such as the Maharashtra Pollution Control Board), but no 'National Pollution Control Board' of Maharashtra, Hyderabad or Allahabad.

Answer: A

The key's answer is the continuously stirred chemical reactor.

Neutralisation of acidic hazardous waste with lime slurry is a chemical treatment. It is carried out in a stirred tank, run in batch or continuous mode, where vigorous mixing keeps the sparingly soluble Ca(OH)₂ suspended and in contact with the waste while the pH is monitored and adjusted.

The other options are not used for this. An immobilised tank holds a fixed catalyst or immobilised cells. A fluidised-bed reactor (spelt 'bead' in the paper) is used mainly for incineration and some biological treatment. An air-lift fermenter is a bioreactor for growing microorganisms. None is the standard vessel for lime neutralisation.

Answer: C

The chemical method is precipitation.

Chemical precipitation adds a reagent such as lime, sodium hydroxide or sodium sulphide to waste water so that dissolved toxic metals form insoluble hydroxides or sulphides. The solids are then separated, which removes the metals from solution. It works through a chemical reaction, so it is classed as chemical treatment.

Sedimentation is physical, simply letting suspended solids settle under gravity. Electrodialysis is a membrane separation driven by an electric field and is classed as physical. Resin adsorption is a physical or physico-chemical separation, binding contaminants onto a resin surface without changing them chemically.