Waste Treatment Technologies Flashcards

What is the primary purpose of the SNCR (Selective Non-Catalytic Reduction) system in a waste-to-energy plant?

Answer: Reduce NOx emissions by injecting ammonia or urea into the furnace

SNCR reduces nitrogen oxides (NOx) by injecting ammonia or urea into the high-temperature furnace zone (850–1100°C), where reagents react with NOx to form nitrogen gas and water without a catalyst.

Which treatment technology converts the organic fraction of municipal solid waste into a soil amendment through controlled biological decomposition?

Answer: All of the above can produce a soil amendment

All three approaches — MBT, anaerobic digestion with digestate composting, and source-separated organics composting — can produce stabilized organic soil amendments when properly designed and operated.

Under RCRA, which treatment standard applies to hazardous debris (contaminated equipment, containers, or soil) before land disposal?

Answer: Debris-specific standards allowing extraction or destruction technologies

RCRA's debris rule (40 CFR §268.45) allows hazardous debris to meet LDR standards through extraction technologies (washing, thermal desorption) or destruction/immobilization technologies specific to debris rather than UTS concentration levels.

What is the function of a refuse-derived fuel (RDF) system in integrated waste management?

Answer: Process MSW to remove non-combustibles and produce a high-energy fuel pellet or fluff

RDF systems shred, screen, and separate MSW to remove metals, glass, and inerts, producing a combustible fraction (pellets or fluff) with higher and more consistent energy content than raw MSW.

Which chemical oxidation reagent is most commonly used for in situ chemical oxidation (ISCO) of chlorinated solvents in groundwater?

Answer: Potassium permanganate

Potassium permanganate (KMnO₄) is widely used in ISCO for chlorinated solvents (PCE, TCE) due to its stability, long persistence in the subsurface, and effective oxidation of the C=C double bond.

A biogas-to-electricity facility generates 500 m³/hour of biogas at 60% methane content. If the electrical conversion efficiency is 35% and methane's heating value is 35.8 MJ/m³, what is the electrical output in kW?

Answer: 1,074 kW

Methane flow = 500 × 0.60 = 300 m³/hr; energy input = 300 × 35.8 MJ/m³ = 10,740 MJ/hr = 2,983 kW; electrical output = 2,983 × 0.35 ≈ 1,044 kW, closest to 1,074 kW.

Which emerging waste treatment technology uses microwave energy to treat medical and pharmaceutical waste without generating dioxins?

Answer: Microwave irradiation treatment systems

Microwave irradiation systems use electromagnetic energy to heat waste internally, achieving sterilization of infectious medical waste without the combustion byproducts (dioxins, furans) associated with incineration.