Pollutants in wastewater -- Revisited

1
Pollutants in wastewater -- Revisited

• Ammonia
• Organic matter
• Nutrients
• Pathogens
• Color
• Metals
• and SUSPENDED SOLIDS

2
Suspended solids

• Reduce water clarity
• Cloudy, gray
• Settle out interfere with aquatic life
• Clog soil and equipment

3
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)

4
Changing the solids content

• Dilution
• Add water
• Farm sources cleaning water, waterer overflows
• Thickening
• Add dry bedding (straw, woodchips)
• Solids separation technologies
• Dewatering

5
Dewatering calculations

• Mass balance Mass in mass out
• Mass Concentration x Volume
• Examples

6
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

7
Overview of methods

• 1. Examples
• 2. Important Management Factors
• 3. Enhancement technologies

8
Force of Gravity examples

• Settling or sedimentation basin
• Primary clarifier
• Septic tank

9
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)

10
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

11
Barriers examples

• Bar racks
• Wire screens
• Hydrosieve
• Fabric filter
• Sand aggregate filter

12
Barriers management factors

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

13
Barriers enhancements

• Increase particle size (coagulation)
• Pressure
• Vacuum
• Series of barriers

14
Thermal treatment examples

• Drying
• Incineration
• Thermal desorption (low heat to volatilize
  organics)
• Freezing

15
Thermal treatment management

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

16
Thermal enhancements

• Use waste heat from other processes
• Use heat exchangers to conserve heat
• Use natural heating processes (ex composting)