Water Quality Parameters
- BOD (Biochemical Oxygen Demand): oxygen consumed by microorganisms to decompose organic matter
- COD (Chemical Oxygen Demand): oxygen equivalent of organic matter oxidized chemically
- DO (Dissolved Oxygen): concentration of oxygen dissolved in water
- TSS (Total Suspended Solids): filterable solids in water (mg/L)
- pH: measure of hydrogen ion concentration; drinking water standard 6.5 to 8.5
- Turbidity: cloudiness measured in NTU (nephelometric turbidity units)
Water Treatment Processes
- Coagulation/Flocculation: add chemicals (alum, ferric chloride) to aggregate particles
- Sedimentation: gravity settling of particles; overflow rate = Q/A
- Filtration: passage through granular media to remove remaining particles
- Disinfection: chlorination, UV, ozone to inactivate pathogens
- Detention time: t = V/Q (volume divided by flow rate)
- Chlorine demand = chlorine dose - chlorine residual
Wastewater Treatment
- Primary treatment: physical removal of settleable solids (removes ~60% TSS, ~35% BOD)
- Secondary treatment: biological processes (activated sludge, trickling filter)
- BOD removal kinetics: L_t = L0 * e^(-k*t) (first-order decay)
- F/M ratio: food-to-microorganism ratio in activated sludge
- SRT (Solids Retention Time): average time sludge stays in the system
- Tertiary treatment: nutrient removal, advanced filtration
Air Pollution
- Criteria pollutants (NAAQS): CO, Pb, NO2, O3, PM (2.5 and 10), SO2
- Emission rate: E = concentration * flow rate
- Gaussian plume model: predicts ground-level concentration from a stack
- Effective stack height: H = h_s + delta_h (physical height + plume rise)
- Control devices: cyclones, baghouses, ESPs, scrubbers
- Collection efficiency: eta = (C_in - C_out) / C_in * 100%
Solid Waste Management
- Municipal solid waste generation: approximately 4.5 lb/person/day in the US
- Waste hierarchy: reduce, reuse, recycle, recover energy, dispose
- Landfill design: liner systems, leachate collection, gas collection, final cover
- Compacted density of MSW in landfill: approximately 800 to 1000 lb/yd^3
- Composting: aerobic decomposition of organic waste
Key Regulations
- Clean Water Act (CWA): regulates discharges into waters of the US; NPDES permits
- Clean Air Act (CAA): sets NAAQS, regulates emissions from stationary and mobile sources
- RCRA: regulates hazardous waste from cradle to grave
- CERCLA (Superfund): cleanup of contaminated sites
- Safe Drinking Water Act (SDWA): sets MCLs (maximum contaminant levels) for drinking water
- NEPA: requires environmental impact statements for federal actions