Introduction to Decentralized Wastewater Management

Ligy PhilipDepartment of Civil Engineering

IIT madras

IntroductionDecentralized wastewater systems collect, treat, and reuse or dispose of wastewater at or near its point of generation.It include systems that treat wastewater from individual homes or buildings as well as cluster systems that treat wastewater from groups of two or more houses.Unlike centralized urban wastewater treatment systems, decentralized systems treat wastewater close to the source, typically using small pipes for collecting small volumes of domestic wastewater.

Most cost-effective option esp in rural areas and hilly terrain. Cost-effectiveness depends on a number of factors like population size and density, topography, distance to an existing centralized system

Introduction (Contd..)

Often more affordable for small communities

Achieves high removal rates for most pollutants

Less hydrological impact

Can be integrated into a flexible wastewater

system

Can be used as a tool to manage development

Advantages of DecentralizedWastewater Treatment

Disadvantages of DecentralizedWastewater Treatment

Potential threat to ground water quality

Can be harder to document treatment

effectiveness

No dilution benefit

Risk of failure concentrated

Requires greater awareness and participation of

homeowners

Less familiar to engineers

Funding challenges

Lack of management structures

Fragmented regulatory structure

Disadvantages of DecentralizedWastewater Treatment

Barriers to Implementation Lack of Knowledge and Public Misperception

Homeowners and developers think that houses with centralized systems will carry higher property values and have greater acceptance

Legislative and Regulatory ConstraintsLack of Management Programs Liability and Engineering Fees Unwillingness of homeowners and developers to accept the liability associated with unfamiliar treatment systems

Financial Barriers The funding agencies generally do not assist privately owned systems.

Decentralized Wastewater Treatment

Reduce sewer networks Simplify sewer by applying SOLID-FREE

SEWER Involve local labour and material available Construct what requires low maintenance and

no energy Generate water and nutrients for irrigation in

agriculture and food-garden

Effective O & M

Properly constituted and staffed DWM [RME] districts and agencies have proven to be an effective means of assuring the long-term performance of onsite [decentralized] systems.

Prince and Davis, 1986

Vision Statement

Large-scale decentralized wastewater management systems should be allowed only if a responsible management agency [district] has been designated.

Crites & Tchobanoglous, 1998

Successful Responsible Management Entities (RME) must include a legal entity that has the technical, managerial, and financial capacity to ensure the viable, long-term, cost-effective, centralized management, operation, and maintenance of decentralized wastewater systems in accordance with appropriate regulations and generally accepted accounting principles.

- Yeager and English, 2001

The EPA reports Decentralized systems are used in 25% of US homes and the

percentage is increasing Decentralized is a permanent part of the Nations wastewater

infrastructure More than half of all septic systems are more than 30 years old

and at least 10% experience a failure every year Adequately managed decentralized systems are a cost

effective long term option for meeting public health and water quality goals

Local governments need a flexible framework and guidance to tailor their management programs to the needs of the community and watershed

Five Management Models

Model 1 - Homeowners Awareness Model 2 - Maintenance Contracts Model 3 - Operating Permits Model 4 - Responsible Management Entity

(RME) Operation and Maintenance Model 5 - RME Ownership

Model 1 - Homeowner Awareness

Individual OSSF owned and operated by homeowners

Use in areas of low environmental sensitivity Treatment technologies limited to

conventional systems Maintenance reminder notification

Model 2 - Maintenance Contract

Homeowner system ownership Professional maintenance Complex OSSF design such as ATU Licensed technicians provide proper and

timely maintenance Individual contracts with individual

homeowners

Model 3 – Operating Permits

Annual permit renewal to assure system performance

Suitable for increased environmentally sensitive areas

Performance based designs with management controls similar to Model 2

Individually owned OSSF systems

Model 4 – Responsible Management Entity Operation and Maintenance

Decentralized systems May be combined with individual OSSF systems Highly reliable operation and maintenance Water quality and sensitive environmental areas Operating permits are issued to the RME instead of

individual homeowners

Model 5 – Responsible Management Entity Ownership

Suitable for decentralized systems Not suitable for individual OSSF’s Systems are owned, operated and maintained by the

RME Removes property owners from responsibility for the

system Greatest assurance of system performance in the

most sensitive of environments

Functions of RME Districts

Asset Inventory System design and installation Plan review & construction inspection Operation and Maintenance Inspections Notification Certification Monitoring Reporting Education

Successful RME Attributes

Governance capacity Technical capacity Managerial capacity Financial capacity

Governance Commonalities

Well defined mission, objectives and goals Sufficient political will exists Preexisting laws sufficient to grant the RME authority to

accomplish it’s mission, objectives and goals Operation outside traditional health department paradigm Big picture focus and NOT micromanagement Set fees and price structure

Technical Commonalities

Biological unit processes Chemical unit processes Mechanical unit processes Component uniformity System type and compatibility

Managerial Commonalities

A paid manager Effective and timely collection enforcement Strong board, annual performance reviews Use generally accepted accounting principles and

good record keeping Strong team of professional consultants Long term and contingency plans

Financial Commonalities

Long-term financial planning Sufficient cash flow to be self-sufficient Establish reasonable and sustainable monthly

charges Independent financial oversight Funds escrowed monthly for replacement

cost Annual audit and performance review

Recommendations for RME’s

Existing development using existing treatment systems – Model 3

Existing development using new treatment systems – Model 4

New development using new treatment systems – Model 5

START

Define Service Area

Determine number of Connections

Sufficient political will exist

Existing laws in place to provide sufficient legal

authority to the new RME

Petition for RME creation and authorities

Develop mission objective &Goals

RME Startup

STOP

Select RME legal structure

Develop required technical, managerial and financial capacity

Develop short and long term plans and Contingencies

This chart makes certain assumptions regarding the

service area and system size, age an type

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Closing Comments

As the ethic of professionalism continues to grow within the industry, there will be an acceleration in the formation of new RME’s. These RME’s can bring tremendous benefits to rural and semi-urban areas by providing effective and efficient wastewater service that protects the public health and environment at an acceptable price.