Introduction to Decentralized Wastewater Management

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Introduction to Decentralized Wastewater
Management

• Ligy Philip
• Department of Civil Engineering
• IIT madras

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Introduction

• Decentralized 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.

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Introduction (Contd..)

• 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

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Advantages of Decentralized Wastewater Treatment

• 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

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Disadvantages of DecentralizedWastewater
Treatment

• Potential threat to ground water quality
• Can be harder to document treatment effectiveness
• No dilution benefit
• Risk of failure concentrated

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Disadvantages of DecentralizedWastewater
Treatment

• Requires greater awareness and participation of
  homeowners
• Less familiar to engineers
• Funding challenges
• Lack of management structures
• Fragmented regulatory structure

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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 Constraints
• Lack 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.

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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

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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

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Vision Statement

• Large-scale decentralized wastewater management
  systems should be allowed only if a responsible
  management agency district has been designated.
• Crites Tchobanoglous, 1998

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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
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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

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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

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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

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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

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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

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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

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Model 5 Responsible Management Entity Ownership

• Suitable for decentralized systems
• Not suitable for individual OSSFs
• 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

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Functions of RME Districts

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

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Successful RME Attributes

• Governance capacity
• Technical capacity
• Managerial capacity
• Financial capacity

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Governance Commonalities

• Well defined mission, objectives and goals
• Sufficient political will exists
• Preexisting laws sufficient to grant the RME
  authority to accomplish its mission, objectives
  and goals
• Operation outside traditional health department
  paradigm
• Big picture focus and NOT micromanagement
• Set fees and price structure

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Technical Commonalities

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

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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

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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

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Recommendations for RMEs

• Existing development using existing treatment
  systems Model 3
• Existing development using new treatment systems
  Model 4
• New development using new treatment systems
  Model 5

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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 RMEs.
  These RMEs 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.

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