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?