Environmental Engineering on the FE Civil Exam
Environmental engineering accounts for 7 to 11% of the FE Civil exam. This section covers water supply and treatment, wastewater treatment, air quality, and solid waste management. Many civil engineers find this area manageable because the problems tend to be conceptual or involve straightforward calculations using well-defined formulas.
Water Supply and Treatment
Water Quality Parameters
Understand the key water quality parameters and their significance:
- Turbidity: A measure of water clarity caused by suspended particles. Measured in nephelometric turbidity units (NTU).
- pH: Measures acidity or alkalinity. Drinking water typically maintained between 6.5 and 8.5.
- Hardness: Caused by dissolved calcium and magnesium ions. Measured in mg/L as CaCO3.
- Total Dissolved Solids (TDS): The total concentration of dissolved substances.
- Coliform bacteria: Indicator organisms for fecal contamination.
Treatment Processes
The conventional water treatment train includes coagulation/flocculation, sedimentation, filtration, and disinfection. Know the purpose and basic design parameters for each unit process:
- Coagulation/Flocculation: Add chemicals (alum or ferric chloride) to destabilize and aggregate suspended particles
- Sedimentation: Allow particles to settle by gravity. Design based on overflow rate (surface loading rate) and detention time
- Filtration: Remove remaining particles by passing water through a granular media bed
- Disinfection: Kill or inactivate pathogenic organisms, typically using chlorine. The CT concept (concentration times contact time) determines disinfection effectiveness
Wastewater Treatment
Wastewater Characteristics
Key wastewater parameters include biochemical oxygen demand (BOD), chemical oxygen demand (COD), total suspended solids (TSS), nitrogen compounds (ammonia, nitrate, organic nitrogen), and phosphorus. BOD measures the oxygen consumed by microorganisms while decomposing organic matter over a standard 5-day period at 20 degrees Celsius.
Treatment Levels
Wastewater treatment occurs in stages:
- Preliminary: Screening and grit removal
- Primary: Sedimentation to remove settleable solids and floating material. Typically removes 50-65% of TSS and 25-40% of BOD.
- Secondary (biological): Biological processes to remove dissolved organic matter. Activated sludge and trickling filters are the most common systems. Typically achieves 85-95% BOD and TSS removal.
- Tertiary/Advanced: Additional treatment for nutrient removal (nitrogen and phosphorus), filtration, or disinfection
For the activated sludge process, understand the key design parameters: food-to-microorganism ratio (F/M), solids retention time (SRT or sludge age), hydraulic retention time (HRT), mixed liquor suspended solids (MLSS), and return activated sludge (RAS) ratio.
Air Quality
The FE Civil exam covers basic air quality concepts including criteria pollutants (particulate matter, ozone, carbon monoxide, sulfur dioxide, nitrogen dioxide, and lead), the difference between primary and secondary pollutants, and basic dispersion concepts. Know that the Gaussian plume model is used to estimate pollutant concentrations downwind of a point source.
Solid Waste Management
Topics include solid waste characterization, collection methods, recycling, composting, and landfill design. Understand the basic components of a modern sanitary landfill: liner system, leachate collection system, gas collection system, and final cover. Know the purpose of each component in preventing groundwater contamination and managing landfill gas.
Mass Balance Approach
Many environmental engineering problems can be solved using the mass balance approach: accumulation equals mass in minus mass out plus generation minus consumption. At steady state, accumulation is zero. Practice applying mass balances to reactors (completely mixed and plug flow) for both water and wastewater treatment calculations.
Exam Preparation Tips
Environmental engineering problems on the FE exam often involve plugging values into standard formulas. Focus on understanding the design parameters for each treatment process and knowing which formula to apply. The FE Reference Handbook provides most of the necessary formulas, so practice using it efficiently. Pay attention to units, especially conversions between mg/L, kg/day, and gallons per day.