ONSITE TREATMENT: Moving toward Sustainability Kreissl.pdf · Better Pretreatment –Fixed-film and...
Transcript of ONSITE TREATMENT: Moving toward Sustainability Kreissl.pdf · Better Pretreatment –Fixed-film and...
DECENTRALIZED TREATMENT:
Moving toward Sustainability
Jim Kreissl
USEPA ORD, retired
WHAT IS “SUSTAINABILITY”?
• Most accept the Brundtland Commission’s
definition:
“…development that meets the needs of
the present without comprimising the
ability of future generations to meet their
own needs.”
Another definition is “meeting the needs of
humans and nature for the long term”
DEPICTION OF SUSTAINABLE
DEVELOPMENT DECISION-MAKING
Social Equity
Environment
Economy
TYPICAL ONCE-THROUGH URBAN
WATER MANAGEMENT SYSTEM
Precipitation Water supply
Urban area
Water returned directly (storm sewers) and indirectly (sanitary sewers)
to surface waters
often several drainage basins downriver from water supply source
HOW DOES SUSTAINABILITY APPLY TO
WATER QUANTITY ISSUES?
• The urban (once-through) approach with conventional centralized technology has proven to worsen soil drying by lowering ground water tables due to infiltration into leaky, deeply-buried (typically 25 ft or more) sewers, while reducing sewer capacity to carry sewage (eg, Boston and Long Island)
HOW BAD ARE THESE LOSSES?
• In the Boston area, 60% of the sewer
capacity is used for carrying “clear water’
from infiltration
• USEPA’s own standards for acceptance of
newly constructed sewers could result in
clear water using 40% of pipe capacity
when the sewer is below the water table
WHAT ARE THE IMPACTS ?
• Residential, agricultural, industrial, and community wells needs to be extended deeper to retain capacity, increasing costs and energy required to operate.
• Cities are asking huge rate-hikes to upgrade existing leaky sewers that mostly carry infiltrated water and to expand treatment facilities that are treating mostly “clear” water.
ANY OTHER WATER QUANTITY
ISSUES?
• Lots!! Starting with stream flow issues…
Because storm-sewer based development
quickly misdirects surface runoff that would
normally infiltrate the soil directly to ground
water, resulting in local stream overflows during
these wet periods and abnormally low flows
during dry ones
• The overall effects include depleted aquifers and
reduced evapotranspiration which can cause
heating and drying of the land
STORMWATER FATE vs
DEVELOPMENT
HOW DOES THIS RELATE TO
WATER QUALITY?
• The biggest source of surface water contamination in the US is storm runoff from agricultural fields and urban areas
• Excessive, first-flush, runoff leads to flashy streams that erode stream banks and become polluted with sediment, pathogens, and nutrients
• Ground water quality degrades faster without dilution from percolation of precipitation that forests, prairies, and other pervious areas provide
TYPICAL RURAL WATER
MANAGEMENT
Water from private/public wells Precipitation
Rural community or single dwelling
Indoor usage returned to
local ground water after soil treatment
Most precipitation and outdoor
usage returned to local ground water
TRADITIONAL SEPTIC SYSTEMS
HOW ABOUT NUTRIENTS FROM ONSITE
WASTEWATER SYSTEMS?
• Modeling data imply onsites can make a major nutrient contribution to nearby surface waters based on their presence in the area
• TMDLs must be performed on local watersheds to show the relative amount of total pollutant contributions that are from septic systems.
• Onsite systems located in riparian zones(especially in karst, fine soils, and steep slopes) can contribute significant levels of nitrogen to receiving waters, so that more complex onsite designs are needed in those areas.
PHOSPHORUS
• Phosphorus is generally removed from the effluent as it passes through the soil after infiltration
• Since P-removal is dependent on soil surface area and reactivity, it generally reduces with time
• Uniform dosing/resting high in the soil profile maximizes the capability to remove P from the effluent.
• If reuse for irrigation is planned, P-removal would be counterproductive
ONSITE SYSTEM MAJOR
CONTAMINANTS
• The primary contaminants from poorly-sited or poorly-performing onsite systems are pathogens, which is the #1 stream contaminant that comes from human wastes and runoff
• In most cases, wastewater nitrogen travels to ground water and then to nearby surface waters fed by those aquifers (controlled by soil characteristics, hydrogeology, and technology)
• Phosphorus is generally removed by local soils
• EDCs and other unregulated chemicals are likely better removed in the soil than by treatment plants
WHAT IS THE
DECENTRALIZED
APPROACH?
• It is a holistic, cost-efficient method of solving
water quality and quantity problems.
• It requires an effective and sustainable
management program.
• It targets the biggest problem areas and
minimizes infrastructure investment.
• It employs simple technologies and maximizes soil
dispersal and reuse opportunities.
TYPICAL CHARACTERISTICS
• CENTRALIZED
– Conventional gravity sewers
– Single treatment facility
– Discharge to surface water
• DECENTRALIZED
– Onsite or alternative collection system
– Multiple treatment facilities
– Discharge to ground water or reuse
Centralized wastewater treatment Decentralized approach
A VISUAL DESCRIPTION
DECENTRALIZED/DISTRIBUTED
PLANNING/DESIGN STRATEGY
• Use the most passive technologies that
can meet performance requirements
• Reuse and aquifer recharge preferred over
conventional receiving water discharge
• Minimize inter-basin transfer of water
• Management program is appropriate to
technologies chosen
• Maximize use of viable existing systems
WHY IS THIS A GOOD THING?
• Existing Communities
Can solve wastewater and other water-related problems.
Minimal initial investment, “satisfy the need”.
• Developers
Allows more lots and greater open space.
Open and common areas can serve as soil dispersal and/or reuse facility locations and social amenities.
Increased developer profits and resident aesthetics.
SO HOW CAN SUSTAINABILITY APPLY TO
ONSITE AND DECENTRALIZED SYSTEMS?
• Local area and watershed management decisions need to be based on sustainable life-cycle costs and energyrequirements of system components, as well as on community protection, vision, and aesthetics
• Distributed wastewater management must be made an integral part of the land-use planning processes, local ordinance upgrades, and state regulations in order to approach sustainability
• Onsite/decentralized systems can minimize energydemands required to maintain performance, promote reuse of wastewater and stormwater, and can be aesthetically pleasing and compatible with any community vision
SO HOW CAN ONSITE AND DECENTRALIZED
SYSTEMS IMPROVE SUSTAINABILITY?
• Compared to conventional sewer systems these technologies minimize the energy required to fabricate, transport, and construct through use of lightweight/recycled components, minimal transport costs/energy, and low-energy, less-time-consuming construction techniques
• Decentralized wastewater and stormwater management approaches minimize impacts on local hydrology and enhance local community aesthetics, health, and economy while assuring needed quantity and quality of water resources to support long-term community goals
CONVENTIONAL SEWERS
THE CONVENTIONAL SEWER SOLUTION
Collection Pipe System – Deep (8 to 25 feet) pipes, with
frequent (every 200-300 feet) manholes, and lift
stations to maintain gravity flow at minimum velocity
(75 to 85% of total facilities cost)
Treatment System – A single large treatment facility,
usually some form of activated sludge, with additional
processes as necessary to meet discharge standards
Discharge - Usually, direct surface water discharge; in
some cases soil discharge is required, but in all cases
extracted waters from several upstream basins are
transferred to one downstream location
COMPARISONS
• CENTRALIZED
• Old and taught
• High capital cost
• Transfers water away
from source
• Long, disruptive
construction
• Skilled operator need
• DECENTRALIZED
• New and not taught
• Lower capital costs
• Keeps water close
• Short, less-disruptive
construction
• Basic operations skills
required
WHICH DECENTRALIZEDTECHNOLOGIES
ARE MOST OFTEN USED?
Septic Systems – Most passive and effective system where local conditions permit.
Better Pretreatment – Fixed-film and filter alternatives are more robust, perform more reliably, and need less O/M than activated sludge types. For special locations, membranes replace settling and attain reuse quality
Better Soil Dispersal – The larger the system capacity, the greater the need for pressurized or drip distribution and resting to maximize soil contact time and treatment potential.
Low-Cost Collection – Minimizes capital and O/M costs, infiltration/inflow, and construction duration and community disruption.
LOW-COST COLLECTION
SYSTEMS
• Alternative collection systems (ACS)
almost always have significantly lower
capital costs
• ACS reduces infiltration and inflow (I/I)
owing to shallow burial, fewer and tighter
joints, and lack of manholes
• Require less community disruption and
construction period duration
Effluent Sewers (STEG and STEP)
LOW-COST COLLECTION SYSTEMS
Effluent Sewer
(STEG)
Composed of:
interceptor tanks (&
pumps for STEP)
Shallow, small dia.
mains w. fewer pipe joints
and cleanouts
LOW-COST COLLECTION SYSTEMS
Composed of:
small-diameter
pressurized
collection system
Grinder/pump
with controls
Like vacuum,
leaves no residuals
on lot
Grinder Pump
To TreatmentGrinder Pump System
Grinder Pump System
Vacuum System is
composed of:
holding tanks
with vacuum valves
Small diameter
collection pipes
Central vacuum
collection
station/no electric
connection on lot
LOW-COST COLLECTION SYSTEMS
Vacuum System
Vacuum Sewers
SINGLE-PASS MEDIA FILTERS
Inlet
Service
ManholeInspection
Riser
Watertight Tank
Outlet
Pipe to
Dispersal
System
VEGETATED SUBMERGED BEDAKA: SUBSURFACE FLOW WETLAND
FLEXIBILITY TO MEET
PERFORMANCE DEMANDS
SOIL DISTRIBUTION
• Better distribution and shallow placement
allows the entire soil infiltration area to be
used:
– provides better oxygen diffusion for aerobic
treatment by microbes
– increases the contact time between the
wastewater and soil, and
– enhances nitrogen removal
PRESSURE DISTRIBUTION
Drip Dispersal
Property Line
Well
Filtration Unit
Pump Tank
House
Shed Drip Tubing
(2 Feet On Center)
Treatment Tank
MANAGEMENT PROGRAM
• Distributed/decentralized solutions require
a responsible management program
• Most surveys show that homeowners are
willing to pay about $30 to $40 per month
for efficient wastewater services (most do)
• The challenge is to develop an effective
and sustainable WATER management
program at the least cost to the community
MORE BASIC MANAGEMENT PRINCIPLES
• The management entity does not need to perform every functional element of their management program. They can contract with trained and certified service providers to perform field work, or require citizens to enter into contracts with those service providers, overseen by the management program
• Keep the community involved on review boards and advisory councils to reinforce their program ownership
• Make compliance rules as friendly as possible, with transparent enforcement and monetary incentives
• Involve the regulators in the process to avoid misinterpretations and build trust.
WHAT ARE SOME TOWNS DOING?
• Converting sludge digesters to co-digestion energy generators by accepting local industrial/commercial organic wastes and producing reusable methane gas
• Reusing stormwater and treated wastewater for irrigationof golf courses and municipal parks and toilet flushing
• Limiting impervious surfaces and storm sewers and maximizing reuse opportunities in new developmentswith cisterns and rain gardens
• Using “just in time” infrastructure investments
• Preserving the most ecologically valuable lands that sequester carbon and promote ecological processes
• Providing economic incentives to reward homeowners and others for incorporating green concepts
WHERE ARE DECENTRALIZED
APPROACHES BEING USED?
• There are scores of such distributed management and decentralized technology solutions employing decentralized technologies across the US
• The following examples are categorized by the types of problems being addressed by them, but many more exist than these.
PROTECTION /RESTORATION OF
SURFACE WATERS
• Lake Panarama, Iowa
• Otter Tail Lake, Minnesota
• Keuka Lake, New York
• Georgetown Divide PUD, California
• Stinson Beach, California
• Charlotte County, Florida
• Nags Head, North Carolina
GROUNDWATER QUALITY PROTECTION
• Block Island, Rhode Island
• Westbrook, Connecticut
• Tisbury, Massachusetts
• La Pine, Oregon
• Willard, New Mexico
MULTIPLE PROBLEMS
• Paradise, California – surface/ground
water quality
• Sea Ranch, California – surface water
quality and hydraulic failures of septics
• Pena Blanca, New Mexico – ground water
quality and hydraulic failures of septics
• Cuyler, New York – surface water quality
and hydraulic failures of septics
THANKS FOR YOUR
ATTENTION
Any Questions?