to Protect Long Island’s...
Transcript of to Protect Long Island’s...
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Onsite Wastewater Treatment Systems
Municipal Officials Conference:
Managing Onsite Wastewater Treatment Systems
to Protect Long Island’s Waters
March 25, 2014
George Loomis
New England Onsite Wastewater Training Program @ URI
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• We are a USDA, state and training class fee funded program
• Outreach through URI Cooperative Extension
• Coverage area: Regions 1&2 – New England, NY, NJ, PR &
USVI
• Provide third party, non-biased technical assistance
• Clientele includes federal and state regulatory agencies,
communities, NGOs, wastewater professionals, homeowners
• Conduct approx. 50 classes a year reaching over 1,800
wastewater practitioners and decision makers
• We perform onsite wastewater research
• Work closely with local and state regulatory programs
NEOWTC @ URI
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Long Island and Block Island Sound
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What we will cover –
1) Conventional OWTS basics
2) Cesspools
3) Contaminant treatment potential
4) System management - inspection and tank
pumping
5) Intro - Advanced treatment technologies (more
in afternoon session talk)
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1) Conventional septic system has
3 main components
Septic tank Soil absorption area
Source: URI Cooperative Extension, New England Onsite Wastewater Training Center
D-Box
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Conventional Septic Tank
Inlet
sludge
scum
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As scum and sludge layers build and come closer
together, the retention time becomes less and
solids removal efficiency drops, as well as BOD and
FOG removal
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Conventional D-Box
Operates on trickle flow
to the lowest pipe invert
D-Box leveling
devices readjust
outlet pipe inverts.
Manufacturers make these for
various pipe sizes.
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Separation distance
Defined as: The distance between the base
of a drainfield and the elevation of
the seasonal high water table (or a
restrictive layer)
This varies with jurisdiction. Nassau Co. has a minimum separation to SHWT of 24”
Suffolk Co. has a minimum separation to SHWT of 36”
Drainfield options
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Drainfield sizing criteria
• Depends on the soil type
• Number of bedrooms
• The design of a soil treatment area also
depends on the type of system.
• Leaching pools are designed differently
than pipe on stone (tile drainfields).
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Min. separation distance to water
table = 3 or 4 feet (Rhode Island)
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• In 2008, galleys prohibited in RI for new construction
• Block Island will phase out existing ones
• Produces a deep
installation base
(8 ft.)
• Poor oxygen
diffusion
• Poor aerobic
treatment
potential
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2’
8’ 2’
10”-14”
3.5’+/-
Alternative system (shallowest chamber type for shallow SHWT)
Leaching pools
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6’
Typical 4 bedroom leaching pool design
(for SHWT 9’ or greater)
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8’
Typical 4 bedroom leaching pool design
(for SHWT 11’ or greater)
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14’
Typical 4 bedroom leaching pool design
(for SHWT 17’ or greater)
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25’ max
A very deep installation
Concentrated footprint
Small infiltrative surface
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• NO septic tank
• Substandard system
• Antiquated and inadequate
• Often violates vertical separation distance regulations
• In coastal areas - may be tidally connected
• Prioritize replacement with approved system
2) Cesspools
Source: URI Cooperative Extension, New England Onsite Wastewater Training Center
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2) Cesspools defined -
Dry-fit, or minimally
mortared: Concrete
block, brick, fieldstone
Into which flows
sanitary sewage from
a structure
Impractical - solids
storage and liquid
infiltration
Treatment and safety
issues
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3) Pollutants common in septic
tank effluent
• TSS, BOD5
• Nutrients - nitrogen, phosphorus
• Volatile organic chemicals (VOCs)
• Pathogenic organisms
- Helminths (septic worms)
- Protozoa
- Bacteria
- Viruses
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Vadose zone wastewater treatment
Controlling factors –
• Environmental
Temp., moisture,
oxygen levels
• Wastewater char.
Loading rates,
strength, types
of pollutants
• Soil properties
Physical, chemical,
biological
• Retention time
Unsaturated soil
Water table
Saturated soil
Biomat
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Soil-based wastewater treatment
The Goal :
• Unsaturated conditions
• Thin film flow of wastewater
around soil particles
• Pore space in between
particles and/or soil peds
(structural units of soil)
• Gases and air move
in/out
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When organic inputs exceed removals and all
soil pore spaces are clogged, then hydraulic
failure occurs.
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Failure defined (usually in regs):
Surfacing wastewater = off site movement of
contaminants, loss of treatment, water quality
impairment, and environmental and public
health risks
Source: URI Cooperative Extension, New England Onsite Wastewater Training Center
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Biochemical reactivity in soils
• 99% of soil bioreactivity is within 10 – 20 inches of soil surface
Sources:
“Introduction to Soil Microbiology”, Second Edition – Martin Alexander - John Wiley & Sons,1977.
"Soil Microbiology" Selman Waksman - John Wiley & Sons, 1952.
MOST OWTS regs promote deep drainfield placement, well below this reactive zone
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Summary - Nitrogen removal in
conventional septic systems
• Less than 15 percent removal in septic tank
• Septic tank effluent composed of organic-N
and ammonium-N
• Limited ammonium adsorption by soil below
drainfield
• Ammonium conversion to nitrate-N
• Nitrate-N very mobile and conservative
• 10 ppm EPA nitrate-N drinking water standard
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Summary - Phosphorus (P) removal in
conventional septic systems
• Phosphorus adsorbed to iron, aluminum,
manganese, calcium, and magnesium in
soils
• P removal depends on soil surface area
• Sands have far less surface area than finer
soil particles
• P saturation can and does occur
• Wet soils conditions result in iron removal, so less P removal potential
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Summary - Wastewater
microorganism movement
Organism Approx. Size Mobility
Potential
Helminths
Protozoa
Bacteria
Viruses
sand
c. silt
f. silt - c. clay
v.f. clay
low
high
Enhanced removals with aerobic soils and long retention times
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Summary –
Emerging contaminants of concern
• Pharmaceuticals
• Antimicrobials
• Endocrine disrupters
• Personal care products (PCPs)
Removals based upon complex biochemistry –
and they are compound and site specific
Aerobic soil conditions and long retention times
are key treatment factors
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Life cycle of an unmanaged
conventional septic system
---------- Years----------
T0 Tff Thf siting
design
permitting
installation
home first
occupied
system
hydraulically
fails
// (first flush)
USE
T = time
4) Management
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The onsite system
O&M image crisis
Anything beyond
nothing seems like
too much !
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Onsite wastewater industry challenge
• Managed centralized treatment plants
• Unmanaged conventional systems
• Managed advanced treatment onsite
systems
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Conventional system inspections and tank pumping
Identifies problems Creates an inventory
Protects –
•Owner investment
•Public health
•Water quality
•Resources
•Property values
Managed systems last longer than neglected ones
Costs - $250 (pumping) and $50 to150 (inspection)
Frequency – every 3 to 5 years
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Onsite Wastewater Treatment System
Inspector Training Class
Dates & Times:
April 22 – 23, 2014 (2-day class) 8:00 am – 5:30 pm (registration at 7:30 am)
or
April 24 – 25, 2014 (2-day class) 8:00 am – 5:30 pm (registration at 7:30 am)
Location:
Oyster Bay Community Center, Church Street, Oyster Bay, NY 11771
Cost: FREE (normal cost $450)
Class size is limited to 25 people, so please register early to assure a seat.
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5) Alternative technology
treatment train
1. Primary treatment zone
2. Alternative technology
Secondary treatment 3. Drainfield - Dispersal and advanced secondary / tertiary treatment 4. Controls - timers
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• Totally unsewered watersheds
• 30 - 50 % of systems are cesspools
• Very permeable unconfined aquifers
• Groundwater contamination risk
• 8 houses / acre on shallow wells
• Surface water eutrophication risk
• Shellfish closures
Water quality standards for coastal pond systems
• 0.3 - 0.5 mg/l TN and 14 counts / 100 ml F. coliform
Typical application for I&A technologies
Rhode Island southern coast
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Advanced treatment technologies approved in RI
ca.1996
• RUCK
• ATUs
• Single pass sand filters
• Recirc. sand filters
• Early textile filters
• Foam biofilters
• Shallow narrow pres. drainfields
• Bottomless sand filters - early
• Modular peat filters
• Textile filters
• Fixed activated sludge systems
• Bottomless sand filters – current
• Denite upflow filters
• Trickling filters
• UV disinfection
• Soil treatment area renovation technologies ca.2014
ca.1983
N removal systems
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Bottomless sand filter
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Thanks for your attention!
George Loomis
401. 874. 4558
http://www.uri.edu/ce/Cwq/OWT/index.htm