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 %handle as solid % slurry (handling varies) %thick liquid (special pumps) %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. Examples 2. Important Management Factors 3. 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 size 1. Flocculation / coagulation aids 2. charged particles / multivalent ions Increase force of gravity example: centrifuge Decrease particle density example: 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)