OR Water/Wastewater Operator cheat sheet

Surface water quality responds rapidly to rainfall and runoff, changing turbidity, color, TOC, and microbial loads; groundwater quality is usually more stable but can contain hardness, iron, manganese, nitrate, or arsenic.

Turbidity is measured in nephelometric turbidity units (NTU) and indicates light scattering by suspended particles; it is not a direct measure of pathogen concentration.

Alkalinity is the acid-neutralizing capacity of water, usually reported as mg/L CaCO3; it buffers pH changes during coagulation and disinfection.

Hardness is primarily dissolved calcium and magnesium, expressed as mg/L CaCO3; it affects soap consumption, scale formation, and softening requirements.

Temperature influences dissolved oxygen solubility, biological growth, reaction rates, and disinfectant decay; colder water holds more dissolved oxygen.

Natural organic matter (NOM), measured as TOC or UV254, reacts with disinfectants to form disinfection byproducts and increases coagulant demand.

pH is a logarithmic scale; a decrease of one pH unit means a tenfold increase in hydrogen ion activity.

Source water assessments and sanitary surveys identify contamination risks such as septic systems, agricultural runoff, and industrial discharges.

Coagulation destabilizes suspended particles by neutralizing negative surface charge; common coagulants include alum, ferric chloride, ferrous sulfate, and polyaluminum chloride.

Jar tests determine optimum coagulant dose and pH by simulating rapid mix, flocculation, and settling on a bench scale.

Rapid mix disperses coagulant quickly; flocculation uses gentle mixing to promote collisions and grow settleable flocs.

Sedimentation basin overflow rate equals flow divided by surface area (Q/A); particles with settling velocity greater than overflow rate are removed.

Granular media filtration removes residual floc and particles; filters are cleaned by backwashing when head loss or effluent turbidity reaches a trigger.

Lime-soda ash softening precipitates calcium carbonate and magnesium hydroxide; excess lime raises pH and requires recarbonation or pH adjustment.

Filter media may include sand, anthracite, and granular activated carbon; GAC also adsorbs organic compounds.

Coagulation pH is critical: alum works best in a relatively narrow pH range, and low alkalinity can require alkalinity supplementation.

Distribution systems must maintain a disinfectant residual and positive pressure to prevent contamination; pressure loss can allow backflow and intrusion.

Water age increases with low demand and long storage; older water can lose disinfectant residual, form DBPs, and support nitrification in chloraminated systems.

Cross-connection control uses air gaps, reduced-pressure zone assemblies, and vacuum breakers to prevent backflow of nonpotable water.

Storage tanks can stratify thermally; mixing or tank turnover helps maintain uniform residual and water quality.

Dead-end mains and low-flow areas accumulate sediment and lose residual; flushing and looping improve water quality.

Corrosion control by pH adjustment, alkalinity adjustment, or inhibitors protects pipe and reduces lead and copper release.

Valves and hydrants require exercising and inspection to ensure operability during emergencies and maintenance.

Storage tank inspection includes checking vents, overflows, hatches, and interior coatings for sanitary defects and corrosion.

Gravity sanitary sewers are designed to flow partially full; minimum self-cleansing velocity is commonly about 2 feet per second at design flow.

Infiltration is groundwater entering sewers through defects; inflow is stormwater entering through direct connections such as roof drains and manholes.

Lift stations use wet wells and pumps to raise wastewater; pump cycling is controlled by level setpoints and should avoid frequent short cycling.

Force mains carry pumped wastewater under pressure; air release and vacuum relief valves protect against air pockets and surge.

Hydrogen sulfide in sewers causes odors, corrosion of concrete, and worker exposure risk; ventilation and chemical addition can control it.

Fats, oils, and grease (FOG) cause blockages; grease interceptors and public education reduce FOG discharges.

Sewer overflows can occur from blockages, infiltration/inflow, or pump failures and must be reported under regulatory programs.

Confined space entry into manholes and wet wells requires atmospheric testing, ventilation, attendant, and retrieval equipment.

Primary treatment removes settleable and floatable solids; primary clarifier performance depends on detention time, overflow rate, and solids loading.

Activated sludge treatment uses aerobic microorganisms to oxidize organic matter; MLSS, DO, SRT, and F/M ratio are key control parameters.

Return activated sludge (RAS) maintains biomass in the aeration basin; waste activated sludge (WAS) controls solids retention time and biomass inventory.

Nitrification converts ammonia to nitrate under aerobic conditions; denitrification converts nitrate to nitrogen gas under anoxic conditions.

Biological phosphorus removal uses anaerobic and aerobic zones; phosphorus-accumulating organisms store phosphorus in excess of metabolic needs.

Sludge thickening, digestion, and dewatering reduce volume and stabilize solids before beneficial reuse or disposal.

Sludge volume index (SVI) indicates sludge settleability; high SVI can signal filamentous bulking and poor clarifier performance.

Trickling filters and lagoons are attached-growth or natural biological systems with different loading and oxygen transfer characteristics than activated sludge.

CT is disinfectant residual concentration multiplied by contact time; required CT depends on disinfectant, pH, temperature, and target pathogen.

Free chlorine is a strong primary disinfectant but forms THMs and HAAs when it reacts with organic matter.

Chloramines provide a more persistent residual but are weaker primary disinfectants and can cause nitrification in distribution systems.

Ozone and UV are strong disinfectants; ozone can form bromate, and UV provides no residual protection.

Breakpoint chlorination is the chlorine dose beyond which free chlorine residual increases rapidly after demand is satisfied.

DBP formation increases with higher TOC, bromide, pH, temperature, and contact time; precursor removal and alternative disinfectants reduce formation.

Trihalomethanes (THMs) and haloacetic acids (HAAs) are regulated groups of disinfection byproducts in drinking water.

Chlorine gas is highly toxic; leak detection, ventilation, and respiratory protection are required for safe handling.

Detention time equals volume divided by flow (t = V/Q); units must be consistent.

Percent removal equals influent concentration minus effluent concentration, divided by influent concentration, times 100.

Loading rate equals flow multiplied by concentration; convert units carefully using 8.34 lb/gal for water-based calculations.

A grab sample represents a single point in time; a composite sample represents an average over time and is used for variable flows.

Sample handling requires proper containers, preservation, holding times, and chain-of-custody documentation.

QA/QC samples include duplicates, blanks, and matrix spikes to assess precision, contamination, and recovery.

Turbidity is measured with a nephelometer calibrated with formazin or polymer standards; pH meters require calibration with fresh buffers.

1 mg/L equals approximately 1 part per million in water; 1 cubic foot equals 7.48 gallons.

Confined space entry requires atmospheric testing for oxygen (19.5–23.5%), flammables, hydrogen sulfide, and carbon monoxide before entry and continuously.

Lockout/tagout isolates hazardous energy sources before maintenance to prevent accidental startup or release of stored energy.

Material Safety Data Sheets or Safety Data Sheets provide hazard, handling, and emergency information for chemicals.

Preventive maintenance includes lubrication, vibration checks, alignment, and inspection to reduce equipment failure.

The Safe Drinking Water Act establishes maximum contaminant levels and monitoring requirements for public water systems.

NPDES permits regulate wastewater discharges and require monitoring, reporting, and compliance with effluent limits.

Emergency response plans address power outages, chemical spills, floods, and loss of treatment or disinfection.

Personal protective equipment must be selected for the task and includes gloves, eye protection, and respiratory protection for chemical exposure.