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Engineering Measurements of Particles

Volumetric measure – Units: mL/L

• Settleable solids– 30 minutes settling in Imhoff cone– Large particles

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Gravimetric measures– mass concentration = mass per volume

of suspensionmg/L = ppm by mass

(approx)

Total solids– Mass of everything except the water– Evaporate the water off; weigh the

residual

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Total suspended solids (TSS)• Filter sample

– 0.45 to 1 m glass fiber filter– Dry at 105C

Tchobanoglous and Schroeder, Water Quality

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Tchobanoglous and Schroeder, Water Quality

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Total dissolved solids (TDS)– What gets through the filter

TS = TSS + TDS– Not truly dissolved -- includes colloids

TSS caught on filter

TDS passes through

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Light scattering

Turbidity• Light scattering at

90 degree angle• Nephelometric

turbidity units (NTU)

Color

Turbidity

Pho

toce

ll

7

Secchi disk clarity• Assesses light penetration in

water• Drop a standard disk into water

until it disappears • Reported as “feet” (e.g., Lake Tahoe exhibits about

65 ft of clarity)

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Chemical Measures• Units for dissolved constituents

– Molar concentration = moles per unit volume

– Mass concentrations = mg/L or g/L• Units for particles

– Mass concentrations = mg/L

Many constituent-specific methods• Standard Methods for the Examination of

Water and Wastewater• EPA Methods

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Inorganic vs. Organic• Volatile Solids (VS)

– Burn off organics at 550CVS = TS - FS

• Volatile Suspended Solids (VSS)– Same thing except we

burn the filterVSS = TSS – FSS

Organics burn off (volatilize)

Fixed (inorganic) solids remain

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Total Organic Carbon (TOC)• Chemically oxidize organics to CO2

• Infrared detector reads the CO2

• Works for:– Dissolved– Small particles

CO2 detector

Sample

Oxidizers (ozone, UV light, hydrogen peroxide, etc.

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Electroconductivity• Conductivity of solution is proportional to

the number of ions• Correlates with TDS

EC

TDS