Pollutants in wastewater -- Revisited Ammonia Organic matter Nutrients Pathogens Color Metals and SUSPENDED SOLIDS

Suspended solids

Reduce water clarity Cloudy, gray

Settle out & interfere with aquatic life

Clog soil and equipment

Solids content

20 - 25% handle as solid 10 - 20% slurry (handling varies)

4 - 10% thick liquid (special pumps)

0 - 4 % liquid (can irrigate or flush)

Changing the solids content

Dilution Add water Farm sources: cleaning water,

waterer overflows Thickening

Add dry bedding (straw, woodchips) Solids separation technologies Dewatering

Dewatering calculations

Mass balance: Mass in = mass out Mass = Concentration x Volume Examples…

Preliminary / Primary Treatment

= Physical separation of solids from water

Methods: Force of gravity Barriers, screens, or filters Thermal (Heat to evaporate water)

Note: this can also apply to sludge treatment

Overview of methods

1. Examples2. Important Management Factors3. Enhancement technologies

Force of Gravity: examples Settling or sedimentation basin Primary clarifier Septic tank

Force of Gravity: management

Residence time (avoid short circuiting) Stillness (avoid turbulence, avoid gas

generation) Solids removal (routinely remove solids for further

treatment and disposal)

Force of Gravity: enhancements

Increase particle size1. Flocculation / coagulation aids2. charged particles / multivalent ions

Increase force of gravityexample: centrifuge

Decrease particle densityexample: Dissolved air flotation

Barriers: examples

Bar racks Wire screens Hydrosieve Fabric filter Sand aggregate filter

Barriers: management factors

Clean the barrier (manual or automatic) Repair filter media Replace filter media Scheduling (of cleaning, repair, &

replacement)

Barriers: enhancements

Increase particle size (coagulation) Pressure Vacuum Series of barriers

Thermal treatment: examples

Drying Incineration Thermal desorption (low heat to

volatilize organics) Freezing

Thermal treatment: management

Heat source or fuel (gas, biogas, solar electricity, etc.) Insulation Air pollution

Thermal: enhancements

Use waste heat from other processes

Use heat exchangers to conserve heat

Use natural heating processes (ex: composting)