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Successful OWTS Treatment. Siting Site Evaluation System Location Design System Sizing System Selection and Design Installation Operation/Maintenance. Failure. A condition that threatens public health by failure to adequately treat sewage or creating potential for direct contact

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Presentation Transcript
Successful owts treatment
Successful OWTS Treatment

  • Siting

    • Site Evaluation

    • System Location

  • Design

    • System Sizing

    • System Selection and Design

  • Installation

  • Operation/Maintenance


Failure
Failure

  • A condition that threatens public health by failure to adequately treat sewage or creating potential for direct contact

  • Examples:

    • Pooling on ground surface

    • Back up into structure

    • Leaking tanks, pump chamber or collection system

    • Impacted water quality (surface or ground)


Factors affecting owts performance
Factors Affecting OWTS Performance

  • Soil system performs multiple tasks in typical OWTS

    • Treat the water to remove contaminants

    • Dispose of treated water

  • Factors that affect these tasks

    Soil Wastewater Characteristics

    Loading Rates Users’ Lifestyle

    O& M Temperature

    Rainfall Surrounding Development


Soil

  • Texture

  • Structure

  • Depth

  • Compaction

  • Landscape Position



Soil horizons soil properties according to depth
Soil Horizons: Soil Properties According to Depth

  • Distinct soil horizons or layers; form from weathering processes

  • Layers have distinct chemical compositions; determines:

    • amounts and state of organic matter

    • amounts of nutrient elements

  • Each layer supports varying amounts and types of microbial communities

    • Surface layers of soils (O layers) are organic

    • Dominated by organic matter (e.g. leaves, twigs, etc.) (= O1 layer)

    • Dominated by unrecognizable organic matter in next lower layer

      • some decomposition has occurred (O2 layer)

    • Sub-surface soil layers (A layers): various combinations of organic and mineral materials which experience increasing amounts of leaching (= eluvial layers)

    • Lower layers (B layers): experience leaching and horizontal movement of materials (= illuvial layers)

    • Lowest soil layers (C layer) experience least weathering; in contact with bedrock


Loading rates
Loading Rates

  • Hydraulic overloading is one of leading causes of OWTS failure

  • Design flow typically based on number of people in house (assumption generally 2 per bedroom)

    • 60 gpd/person (common assumption in design)

  • Loading rates determined by type of soil


Loading rates1
Loading Rates

  • Clogging Mat

  • Gravitational potential

  • Matric Potential


Users lifestyle
Users’ Lifestyle

  • Low-flow devices (toilet, faucets, shower heads, etc.)

  • Rainfall collection

  • Use of garbage disposals

  • Excessive use of FOG

  • Laundry habits

  • Time in Residence


Wastewater characteristics
Wastewater Characteristics

  • BOD5 (above 230mg/L will reduce life of system and level of treatment)

  • Biologically active chemicals (bleach, antibiotics, etc.)

  • FOG

  • Other chemicals (Cleaners, solvents, degreasers, etc.)


Operation and maintenance o m
Operation and Maintenance (O&M)

  • Pump Tanks every 3 to 5 years (plan on every 4)

    • Actual time period should depend on active monitoring of system

  • Conduct at least biannual monitoring of tank levels, baffles, and drainfield

    • This is the minimum, more frequent monitoring recommended (required for advanced systems)

    • Pump tank when sludge layer thickness exceeds 25% of working liquid capacity of the tank, or if scum layer is within three inches of bottom of outlet baffle



Temperature and rainfall
Temperature and Rainfall

  • Temperature

    • Affects flow and mixing in septic tank

    • Soil treatment relies on biological activity

    • Cold slows down biological processes

      • 50% loss in activity for 10ºC drop in temp

      • Activity effectively stops at 2 ºC

  • Rainfall

    • Additional hydraulic load on soil

    • Reduction in vertical separation

    • Benefit-dilute nitrates, however also increase transport rate


Alternative waste treatment
Alternative Waste Treatment

  • Stabilization Ponds

  • Wetlands

  • Composting Toilets

  • Separation of Waste Streams

  • Greywater Sytstems

  • Primitive Systems



Stabilization ponds or lagoons
Stabilization Ponds or Lagoons

  • Aerobic and Facultative Ponds:

  • Biologically Rx by complementary activity of algae and bacteria.

  • Used for raw sewage as well as primary‑ or secondary‑Rx’d. effluent.

  • Bacteria and other heterotrophs convert organic matter to carbon dioxide, inorganic nutrients, water and microbial biomass.

  • Algae use CO2 and inorganic nutrients, primarily N and P, in photosynthesis to produce oxygen and algal biomass.


Stabilization ponds or lagoons1
Stabilization Ponds or Lagoons

  • Many different pond designs have been used to treat sewage:

  • facultative ponds: upper, aerobic zone and a lower anaerobic zone.

  • Aerobic heterotrophics and algae proliferate in the upper zone.

  • Biomass from upper zone settles into the anaerobic, bottom zone.

  • Bottom solids digested by anaerobic bacteria.


Constructed wetlands and enteric microbe reductions
Constructed Wetlands and Enteric Microbe Reductions

  • Surface flow (SF) wetlands reduce enteric microbes by ~90%

  • Subsurface flow (SSF) wetlands reduce enteric microbes by ~99%

  • Greater reduction in SSF may be due to greater biological activity in wetland bed media (porous gravel) and longer retention times

  • Multiple wetlands in series incrementally increase microbial reductions, with 90-99% reduction per wetland cell.


Primitive systems

Outhouses

Privy

Throne

Palace

Comfort station

Castle

Post office

Johnny

Stool

Doolie

White house

Hut

WC

Ajax

Bog House

Defacatorium

Primitive Systems


Mr turdley says don t be a fecaphobe
Mr. Turdley Says-“Don’t be a fecaphobe”


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