Physical/Chemical Industrial Waste Treatment Operator flashcards

33 cards. Read the term and the definition here. The deck at the top of this page is optional.

IDLH H2S concentration

The immediately dangerous to life or health concentration for hydrogen sulfide is 100 ppm; entry requires supplied air and confined-space procedures.

Oxygen deficiency threshold

An atmosphere below 19.5% oxygen is oxygen-deficient and prohibits entry; above 23.5% is oxygen-enriched and raises fire risk.

Methane LEL

Methane's lower explosive limit is 5% by volume in air; combustible-gas meters read 0-100% LEL, and entry is barred above 10% LEL.

Hypochlorite and acid mixing hazard

Mixing sodium hypochlorite with acid releases chlorine gas; oxidizers and acids must be stored and fed separately to prevent toxic gas generation.

BOD5 definition

Biochemical oxygen demand measured over 5 days at 20 °C, reflecting oxygen consumed by microorganisms degrading biodegradable organic matter in the sample.

COD versus BOD

COD measures oxygen demand of both biodegradable and non-biodegradable matter via dichromate digestion; BOD measures only the biodegradable fraction.

BOD5/COD ratio

A ratio near 0.4-0.6 indicates good biodegradability; below about 0.3 suggests poorly biodegradable waste and limited biological treatability.

TSS measurement method

Total suspended solids are determined by filtering through a glass-fiber filter and drying at 103-105 °C; the residue is reported in mg/L.

Equalization tank purpose

Equalization tanks damp flow and concentration swings from batch industrial discharges, protecting downstream biological and chemical processes from shock loads.

Clarifier overflow rate

Overflow rate in m3/m2·d governs particle removal in gravity clarifiers; solids loading rate in kg/m2·d governs thickening performance.

Stokes' law settling

Particle settling velocity increases with the square of particle diameter and the density difference between particle and fluid, and decreases as viscosity rises.

DAF recycle ratio

Dissolved air flotation uses a pressurized recycle stream, typically 20-50%, to generate microbubbles that lift low-density solids and FOG.

Activated carbon breakthrough

The point where effluent contaminant concentration rises sharply as adsorption capacity is exhausted, signaling carbon replacement or regeneration.

Coagulation versus flocculation

Coagulation destabilizes colloidal charge with alum, ferric salts, or polymers; flocculation gently mixes to grow settleable flocs.

Jar test purpose

A bench test that varies coagulant dose and mixing to identify optimal chemical dose; overdosing can reverse charge and re-stabilize particles.

Hexavalent chromium reduction

Cr(VI) is reduced to Cr(III) at pH 2-3 using bisulfite or ferrous sulfate, then precipitated as Cr(OH)3 near pH 8-9.

Amphoteric metal precipitation

Most heavy metals precipitate as hydroxides near pH 8-10; zinc and lead redissolve at higher pH, so pH control must be tight.

Lime softening pH

Lime raises pH to precipitate CaCO3; removing magnesium requires pH above about 10.5 to form Mg(OH)2.

Sludge volume index formula

SVI = settled sludge volume (mL/L) × 1000 / MLSS (mg/L); 80-150 mL/g indicates good settling, higher values suggest bulking.

F/M ratio

Food-to-microorganism ratio: organic mass fed per day divided by microorganism mass; high F/M risks bulking, low F/M favors nitrification.

MCRT definition

Mean cell residence time equals the mass of solids in the system divided by the mass wasted plus lost per day, controlling sludge age.

pH meter calibration

pH meters require two-point calibration with fresh buffers, typically pH 4 and 7 or 7 and 10, and storage in KCl solution rather than distilled water.

Cavitation cause

Cavitation occurs when available NPSH falls below required NPSH, causing vapor bubbles to collapse; it sounds like gravel and damages impellers.

Pump priming loss

Loss of prime results from air leaks, a worn seal, or a dry suction; vent the casing and check suction lines before assuming mechanical failure.

Centrifugal pump throttling

Centrifugal pump flow is controlled with a discharge valve; throttling the suction valve risks cavitation and must be avoided.

LOTO purpose

Lockout/tagout isolates and verifies zero energy before maintenance on rotating or electrical equipment, preventing accidental startup and injury.

Cake solids calculation

Sludge mass to haul equals dry solids mass divided by the cake solids fraction; raising cake percent directly reduces hauling volume and cost.

Mesophilic digestion temperature

Anaerobic mesophilic digestion operates near 35 °C; stable temperature and feed prevent souring and maintain methane production.

40 CFR Part 503

The federal rule governing biosolids land application, setting pathogen reduction and vector attraction reduction requirements for sludge use.

Manning's equation

Gravity sewer velocity: v = (1.486/n) R^(2/3) S^(1/2) in US units; self-cleansing velocity is about 0.6 m/s (2 ft/s).

Weir and flume flow

Open-channel flow is measured with a weir or Parshall flume; flow rate is computed from measured head using the structure's rating equation.

Secondary containment sizing

Storage tank containment must hold the largest tank volume plus precipitation allowance, preventing incompatible or hazardous releases from escaping.

Discharge monitoring report

The DMR reports NPDES effluent monitoring results, typically monthly; violations require notice to the permitting authority within the permit-specified time.