ABC Wastewater Collection Class II cheat sheet
ABC Wastewater Collection Class II · Keep the key ideas within reach.
Collection System Operations and Maintenance
Sewer cleaning methods: hydraulic (flushing), mechanical (rodding, augering), and chemical; choose based on pipe size, blockage type, and access.
Preventive maintenance schedules: inspect and clean lines on a frequency based on pipe material, age, slope, and history; typical frequencies range from monthly to every 5 years.
Root control: use mechanical cutting or chemical foaming; repeat as needed, especially in areas with mature trees.
Grease control: implement grease trap ordinances, public education, and regular inspection of food service establishments.
Infiltration and inflow (I/I): identify via smoke testing, dye testing, and flow monitoring; repair defective pipes and manholes.
Manhole inspection: check for cracks, corrosion, inflow sources, and proper cover fit; repair or replace as needed.
Safety: follow confined space entry procedures for manholes and wet wells; use gas monitoring and ventilation.
Recordkeeping: maintain accurate records of maintenance activities, inspections, and repairs for asset management and regulatory compliance.
Emergency response: have a plan for sanitary sewer overflows (SSOs), including containment, cleanup, and public notification.
Sewers, Lift Stations, and Pumping Equipment
Sewer types: sanitary, storm, and combined; sanitary carries wastewater to treatment, storm carries runoff, combined carries both.
Lift station components: wet well, pumps, motors, controls, valves, and emergency power; designed to lift wastewater when gravity flow is not possible.
Pump types: centrifugal, positive displacement, and submersible; selection depends on flow, head, and solids handling.
Pump maintenance: regular inspection of impellers, seals, bearings, and check valves; monitor vibration and temperature.
Wet well cleaning: remove grit and debris to prevent pump clogging and reduce wear.
Odor control: use covers, ventilation, and chemical addition (e.g., hydrogen peroxide, ferrous chloride) to reduce H2S.
Emergency power: test generators regularly; ensure automatic transfer switches function properly.
Level controls: maintain float switches, ultrasonic sensors, and pressure transducers; calibrate as needed.
Safety and Confined Space Entry
Confined space definition: limited entry/exit, not designed for continuous occupancy, and large enough to enter; includes manholes, wet wells, and tanks.
Entry permit required for permit-required confined spaces; permit includes hazards, atmospheric testing, ventilation, and rescue plan.
Atmospheric testing order: test oxygen first (19.5-23.5%), then flammables (<10% LEL), then toxics (H2S <10 ppm, CO <35 ppm).
Ventilation: use forced air blowers before and during entry; test atmosphere continuously.
Rescue: trained attendant outside; retrieval systems (tripod, winch) for non-entry rescue; entry rescue only by trained personnel.
Personal protective equipment (PPE): hard hat, safety glasses, gloves, steel-toe boots, and respiratory protection as needed.
Lockout/tagout: isolate energy sources (pumps, mixers) before entry; verify zero energy.
Hazard communication: know chemical hazards (H2S, methane, chlorine) and use appropriate monitoring and PPE.
Wastewater Flow, Hydraulics, and Capacity
Flow measurement: use weirs, flumes, or flow meters; calibrate regularly.
Manning's equation: Q = (1.486/n) * A * R^(2/3) * S^(1/2) for open channel flow (English units).
Pipe capacity: Q = A * V; velocity should be between 2 ft/s (scouring) and 10 ft/s (erosion) for sanitary sewers.
Slope: minimum slope for 8-inch pipe is typically 0.4% (0.004 ft/ft) to maintain self-cleansing velocity.
Infiltration/inflow: peak flows can exceed dry weather flow by 3-5 times; design capacity must account for this.
Hydraulic grade line (HGL): represents energy grade; must be below manhole rim to prevent surcharging.
Pump curves: system curve intersects pump curve at operating point; adjust impeller or speed to change flow.
Capacity assessment: use flow monitoring and modeling to identify bottlenecks and plan upgrades.
Inspection, Testing, and Rehabilitation
CCTV inspection: identifies defects (cracks, roots, offsets, infiltration); record and code per NASSCO PACP.
Smoke testing: blows smoke into sewer to find inflow sources; notify public and fire department beforehand.
Dye testing: confirms connection of illegal drains or inflow sources; use non-toxic dye.
Leak testing: low-pressure air test or water exfiltration test for new or repaired pipes.
Rehabilitation methods: CIPP (cured-in-place pipe), slip lining, pipe bursting, and spot repairs.
Manhole rehabilitation: use cementitious liners, epoxy, or polyurethane to seal and restore structure.
Trenchless technologies: minimize excavation and disruption; suitable for urban areas.
Quality assurance: verify rehabilitation by post-inspection (CCTV) and testing.
Regulations, Permits, and Reporting
NPDES permit: required for discharge from wastewater treatment plants; includes effluent limits and monitoring requirements.
SSO reporting: report sanitary sewer overflows to state agency within specified time (often 24 hours); include volume, location, and corrective actions.
Collection system permits: some states require permits for collection systems (e.g., California SSO Reduction Program).
Pretreatment regulations: 40 CFR Part 403; local limits for industrial users; permits and monitoring.
Biosolids regulations: 40 CFR Part 503; classify and manage biosolids according to pathogen and vector attraction reduction.
Operator certification: required by state; Class II certification for collection system operators.
Recordkeeping: retain monitoring records for at least 3 years (or longer per permit).
Public notification: for permit violations and SSOs, notify public and affected parties as required.
Math and Calculations
Flow rate: Q = V * A; convert units (1 cfs = 448.8 gpm; 1 MGD = 1.547 cfs).
Detention time: t = Volume / Flow; ensure consistent units.
Velocity: V = Q / A; for circular pipe flowing full, A = π * (D/2)^2.
Slope: S = (elevation difference) / (horizontal distance); express as ft/ft or percent.
Pump horsepower: HP = (Q * H * SG) / (3960 * efficiency) for centrifugal pumps (Q in gpm, H in feet).
Chemical dose: lbs = (concentration, mg/L) * (volume, MG) * 8.34.
Population equivalent: BOD5 contribution per person = 0.17 lb/day; use for loading calculations.
Unit conversions: 1 cubic foot = 7.48 gallons; 1 gallon = 8.34 lbs (water).
Area of circle: A = π * r^2; circumference: C = π * D.
Pretreatment, Grease, and Odor Control
Pretreatment program: controls industrial discharges to protect treatment plant and receiving waters; includes permits, monitoring, and enforcement.
Local limits: developed to prevent pass-through, interference, and sludge contamination; based on plant capacity and receiving stream.
Grease trap/interceptor: required for food service establishments; size based on flow and retention time; maintain regularly.
FOG (fats, oils, grease) control: public education, ordinance, and inspection; prevent blockages and SSOs.
Odor control methods: chemical addition (chlorine, hydrogen peroxide, ferrous salts), biofilters, and covers.
Hydrogen sulfide (H2S) control: reduce sulfide generation by minimizing detention time, adding nitrate, or using iron salts.
Corrosion control: H2S converts to sulfuric acid, damaging concrete; use corrosion-resistant liners or coatings.
Monitoring: sample industrial discharges for pH, BOD, TSS, metals, and toxic organics as required by permit.
Recordkeeping, Asset Management, and Public Relations
Asset management: inventory assets, assess condition, prioritize maintenance, and plan capital improvements.
Computerized maintenance management system (CMMS): track work orders, inventory, and maintenance history.
Recordkeeping: maintain as-builts, inspection records, maintenance logs, and monitoring data; retain per regulations.
Public relations: communicate with public about projects, SSOs, and rates; use door hangers, websites, and public meetings.
Customer service: respond promptly to complaints (odors, backups); document and follow up.
Emergency notification: use reverse 911, social media, and signage to inform public of SSOs or health hazards.
Rate setting: ensure sufficient revenue for operation, maintenance, and capital improvements.
Performance measurement: track SSOs, backups, inspection completion, and customer complaints to improve service.