3.1 Characteristics of Source Water & Contaminants

3.1 Characteristics of Source Water & Contaminants

Quick Answer: Source-water quality is described by physical parameters (turbidity, color, temperature, taste/odor), chemical parameters (pH, alkalinity, hardness, TOC, iron, manganese, chloride, nutrients), and biological parameters (bacteria, viruses, protozoa, algae). Those characteristics determine which treatment barriers Florida plants must run and how operators set coagulant dose, oxidant demand, CT, and DBP control strategy.

Characteristics of Source Water and Reservoir and Well Field Management appear on FDEP Class B and Class C drinking-water treatment outlines. On the exam, questions rarely ask for isolated definitions—they ask what an operator should do when raw turbidity spikes after a storm, when iron rises after a well is idle, or when high TOC threatens Stage 1/2 DBP compliance. Treat every parameter as a process-control signal.

Why Source Characterization Comes First

Drinking-water protection uses a multi-barrier approach: source protection → treatment → disinfection → distribution integrity. Source characterization is the foundation of that chain. A utility that understands its raw water can:

• Select the correct process train (or justify a process change)
• Size chemical feed systems and contact basins
• Anticipate seasonal load changes (hurricanes, drought, algae seasons, spring turnover in surface supplies)
• Satisfy FAC 62-550 monitoring and treatment-technique requirements that implement the Safe Drinking Water Act

Most Florida public water systems rely primarily on groundwater. Many small systems are a well (or wellfield), disinfection, and distribution. Larger utilities and some coastal systems blend groundwater, surface water, and desalinated or brackish RO product. Operators still need full surface-water vocabulary because Class C exams cover both source types and because GWUDI wells are regulated as surface water.

Physical Characteristics

Turbidity

Turbidity measures light scattering by suspended particles (clay, silt, organic debris, microorganisms) in nephelometric turbidity units (NTU). High turbidity:

• Indicates particulate loading that may carry pathogens
• Shields microorganisms from free chlorine and other disinfectants
• Increases coagulant demand and filter loading
• Triggers operational alarms and compliance risk on filtered systems

Typical Florida pattern:

Under the Surface Water Treatment Rule framework used for surface and GWUDI sources, combined filter effluent turbidity performance (commonly ≤ 0.3 NTU in at least 95% of monthly measurements and never exceeding 1.0 NTU for conventional/direct filtration plants under current EPA criteria operators are tested on) is a treatment-technique surrogate for pathogen removal. Know the concept even if your plant is a clear groundwater system.

Color

Color is reported in platinum-cobalt (Pt-Co) units and is split into:

• Apparent color — measured on the unfiltered sample (dissolved + suspended matter)
• True color — measured after filtration/centrifugation removes suspended solids (dissolved matter only)

Florida surface waters and some shallow groundwater near wetlands can show tea-colored water from natural organic matter (tannins, humic/fulvic acids). Color is not just cosmetic: dissolved organic matter contributes to TOC, raises disinfectant demand, and forms trihalomethanes (TTHMs) and haloacetic acids (HAA5) when chlorinated.

Temperature, Taste, and Odor

Temperature affects reaction rates (coagulation, disinfection CT tables, biological activity). Taste and odor compounds of exam importance include geosmin and 2-methylisoborneol (MIB) from cyanobacteria/actinomycetes, and hydrogen sulfide (H₂S) from anaerobic groundwater or hypolimnion release. H₂S is classic Florida well-water chemistry in some aquifers and is managed with aeration/oxidation and pH control—not with “more chlorine” alone if demand and DBPs will suffer.

Chemical Characteristics

pH

pH is the hydrogen-ion activity scale. It controls:

• Coagulant performance (alum works best in a defined pH window)
• Disinfection effectiveness (free chlorine is more effective at lower pH because HOCl predominates)
• Corrosion control and lead/copper risk
• Lime softening chemistry and recarbonation needs

Operators track raw and finished pH continuously or frequently; sudden raw pH shifts after storms or well changes should trigger jar tests or process review.

Alkalinity

Alkalinity is the water’s acid-neutralizing capacity, typically expressed as mg/L as CaCO₃. It buffers pH during coagulation and chemical addition. Low-alkalinity water may need alkali addition (lime, soda ash, caustic) so alum or ferric coagulation can work without crashing pH. High alkalinity may favor different coagulant choices or doses. Exam questions often pair alkalinity with jar-test results and coagulant dose math.

Hardness

Hardness is primarily calcium and magnesium. Hard groundwater is common in Florida limestone aquifers. Effects:

• Scale in heaters and pipes
• Soap scum and customer complaints
• May drive lime softening or ion exchange at some plants
• Interacts with corrosion-control strategy (softened or low-alkalinity water can be aggressive if not stabilized)

Hardness is often grouped with alkalinity and pH when evaluating stability indices, but on Class C exams the first-order idea is “hardness = Ca + Mg; soft vs hard drives treatment choice.”

Total Organic Carbon (TOC)

TOC quantifies organic carbon and is central to DBP precursor control. High-TOC raw water chlorinated without TOC removal can fail Stage 1/2 DBP MCLs in the distribution system months later. Conventional plants use enhanced coagulation/softening TOC removal percentages based on raw TOC and alkalinity; many Florida utilities also use GAC, membranes, or chloramine residual strategies. When an exam scenario lists rising raw TOC after a hurricane or after drawing from a tannic surface source, the correct operational theme is DBP risk and precursor removal, not only color complaints.

Other Chemical Contaminants Operators Track

Distinguish primary standards (health-based MCLs/treatment techniques) from secondary standards (aesthetic/cosmetic, e.g., iron 0.3 mg/L SMCL, manganese 0.05 mg/L SMCL, chloride 250 mg/L SMCL—values operators commonly memorize). Florida implements federal standards through FAC 62-550.

Biological Characteristics & Pathogen Groups

Pathogens of drinking-water importance fall into three exam groups:

1. Bacteria — e.g., pathogenic E. coli, Salmonella, Shigella, Vibrio. Indicator monitoring uses total coliform / E. coli under the Revised Total Coliform Rule framework.
2. Viruses — e.g., norovirus, enteroviruses, hepatitis A. Smaller and generally more chlorine-susceptible than protozoan cysts; CT tables credit virus inactivation.
3. Protozoa — Giardia lamblia and Cryptosporidium. Cysts/oocysts are relatively chlorine-resistant; removal relies heavily on physical treatment (coagulation + filtration) and, where used, UV or ozone. Cryptosporidium is a signature reason turbidity performance and watershed/GWUDI control matter.

Algae and cyanobacteria are biological source issues that create filter clogging, taste/odor, and sometimes toxins. Surface-water plants manage them with intake depth selection, copper sulfate or alternative algaecides (respecting alkalinity and aquatic toxicity), PAC, and oxidation strategies.

Groundwater that is truly isolated often has negligible turbidity and microbial counts, but karst Florida geology can short-circuit surface microbes into wells—hence GWUDI determinations (covered in §3.2).

Organic vs Inorganic Contaminants

• Inorganic — minerals and ions: hardness metals, iron, manganese, chloride, nitrate, arsenic, lead/copper (often from plumbing, not the source), fluoride.
• Organic — natural organic matter (NOM/TOC/color), synthetic organic chemicals (pesticides, solvents), and disinfection byproduct precursors.

Operators also classify pollution as:

• Point source — discrete discharge (WWTP outfall, industrial pipe, spill)
• Nonpoint source — diffuse runoff (agriculture, urban stormwater, septic fields)

Florida source protection often focuses on wellhead protection areas, springsheds, fertilizer BMPs, and septic-to-sewer projects near impaired springs—not only industrial NPDES pipes.

How Raw Water Quality Drives Process Selection (Exam Scenarios)

Think in decision trees the way Class C items are written:

Scenario A — Clear, hard, sulfurous well water
Low turbidity, H₂S odor, Fe/Mn present when oxidized. Train: aeration → oxidation → filtration (if needed) → disinfection → stabilization. Softening only if hardness policy/customer needs require it.

Scenario B — Storm-driven canal water, high turbidity and TOC
Conventional train: coagulation → flocculation → sedimentation → filtration → disinfection, with jar tests after each storm pulse; watch DBP precursors and filter effluent turbidity.

Scenario C — Coastal wellfield with rising chloride
Not fixed by “more chlorine.” Responses: reduce pumping, rotate inland wells, blend, investigate saltwater intrusion, consider RO for brackish sources, coordinate with the Water Management District consumptive use permit.

Scenario D — Colored, high-TOC groundwater with stable turbidity
May need organics-focused treatment (enhanced coagulation if particulate/organic combined, GAC, membranes, or alternative disinfectant residual strategy) because chlorination alone can create DBP compliance failures.

Scenario E — Well turbidity spikes hours after heavy rain
Treat as potential surface influence / GWUDI investigation—not a routine chemical-dose tweak only.

Monitoring Habits That Score Points on the Exam

• Sample raw water often enough to see change (continuous online turbidity/pH where installed; grab samples for Fe, Mn, hardness, alkalinity, chloride, TOC on a scheduled program).
• Correlate weather, well run times, and water-level data with chemistry.
• Use jar tests when source quality shifts—not only when filters look dirty.
• Recordkeeping supports both process control and regulatory reporting.

Master the vocabulary in this section, then map each parameter to a treatment response. That mapping is what FDEP Class C items test under Characteristics of Source Water.