The Benefits of the Decentralized Option

By PIO LOMBARDO

The Decentralized Wastewater Management Option for Los Osos would consist of a number of communal neighborhood systems serving all existing developed properties and build-out by complete wastewater collection, treatment and dispersal systems.
    
The number of communal/neighborhood systems is to be determined. Each system would serve different neighborhoods that could be represented by a homeowners association or the CSD. It is not unreasonable, nor does it cause management difficulties, for there to be 25+/- neighborhood systems.
    
The Decentralized Wastewater Management Option would produce reusable water complying with CA Title 22 standards for unrestricted water reuse. Use of the untreated wastewater for residential landscape irrigation—which represents approximately 50% of the Los Osos water use—would solve the water supply imbalance in Los Osos that has caused saltwater intrusion and thereby endangering the community’s groundwater water supply, as well as reducing in half on average, Los Ososean’s water supply costs. No other proposed wastewater solution meets the necessary performance criteria to restore the community’s water supply.
    
The Decentralized Wastewater Option would consist of a number of communal wastewater systems that would total the wastewater design flow of 1.2+/- MGD. Each communal system would consist of the following components:

Collection

- Septic Tank Effluent Collection System – maximizing the use of gravity (i.e. STEG) and using pumps (STEP) when necessary. Placing STEPs everywhere is an unnecessary expense and energy use.

- House Connection – all work associated with connecting an existing house’s septic system to the communal/neighborhood system is included. There are no additional costs to be borne by the homeowner.

Treatment

- Recirculating Media Filters for Advanced Secondary Treatment
- NitrexTM system for nitrogen removal – which could have emergent wetlands if desired
- isinfection with UV-Ozone that additionally treats for the emerging contaminants

Reuse/Dispersal

- Primarily by returning the treated wastewater to the individual properties generating wastewater, for drip/landscape irrigation. Additional drainfields would be provided for “excess” treated effluent that is not disposed of via drip irrigation to individual wastewater generating properties. Drip irrigation is a year-round activity and not subject to seasonal issues associated with surface land application, i.e. spray irrigation as proposed by others. Connection between communal systems for effluent reuse/dispersal would occur to address wastewater production-reuse/dispersal imbalances in communal areas.

Siting

Sufficient undeveloped land exists throughout the community to site the needed communal wastewater treatment facilities. At each of the communal treatment sites, virtually all wastewater treatment facilities would be below ground. With appropriate landscaping, the communal systems could be an open space amenity in the community and/or sites for solar collectors to reduce energy costs.

Operation & Maintenance

Operation and maintenance of the communal wastewater systems is simple, requiring little operator attention. Current comparable facilities operate with monthly visits. Monitoring requirements will require simple sampling. Electrical needs are predominately to operate small pumps that operate intermittently. No chemicals are needed. There is little sludge production in the treatment system. Odor issues are mitigated as there is no sludge processing and natural passive soil filters are used for purifying air venting of treatment processes.  

Benefits of the Decentralized Option:
1. Cost competitive – less costly
    Some centralized wastewater systems costs are eliminated or traded for more productive/valued uses, such as:
a. Elimination of force main to treatment plant
b. Dispersal system and land costs are traded for a water reuse/drip irrigation system that lowers property owners’ water supply costs by 50% +/- on average. This feature should also increase property values.
c. Eliminates the saltwater intrusion problem and restores the sustainability of the community’s water supply. It is noted that landscape irrigation is 50% of water use in Los Osos, and is the major cause of saltwater intrusion.
d. Eliminates centralized sludge treatment, usually a major source of odors and costs. Sludge generated will be predominately septage (septic tank pumping), which can be treated by simple subsurface land application or disposal at an existing centralized wastewater treatment facility.
e. Using the unit costs in the Los Osos Wastewater Project Viable Project Alternatives Fine Screening Analysis (FSA) and our experience for items not included in the FSA, the Decentralized Wastewater Option is cost competitive with the centralized options and with the reuse component, provides more for less.
f. GUARANTEED PRICE – the capital and annual operation costs will be guaranteed
2. Implementation Speed – the communal system modularity enables the project to be easily segmented and the individual communal systems can be implemented quickly.  
3. Environmental Benefits
a. Low energy use – low carbon footprint with use of solar collectors possible
b. No chemicals needed
c. Working within existing developed area, thereby eliminating impacts on new sites
d. Treated wastewater must be re-used for landscape irrigation for a sustainable community. The decentralized option is the only solution proposing this approach.
e. Treats emerging contaminants
4. Technical Issues
a. Gravity septic tank effluent collection systems do not have the infiltration problems of conventional systems.
b. Treatment processes are all low-energy use systems.
5. Financing
a. Private financing is available
6. Affordability
a. The decentralized option addresses both wastewater and supply issues and thereby eliminates unknown future costs associated with addressing the water supply salt water intrusion problem.
b. Reduces water supply costs by 50%. Consequently, future water supply escalation costs will not be as severe. Also, the value of reuse increases as water supply costs increase.
c. Least cost option for capital and annual Operation & Maintenance costs. Due to low energy use, no chemicals and simple operations, impacts of future inflation are reduced.
7. Groundwater Recharge/Reuse
a. The decentralized option is the only option that solves water supply imbalance at no additional cost.
8. Sustainability
a. Uses passive low-energy system
b. Avoids unnecessary pumping with out of town facility and unnecessary STEP units
c. Restores community’s water supply

Pio Lombardo is President of Lombardo Associates, Inc. of Malibu, Calif., and Boston, Mass., has completed a system in Malibu identical to what he is proposing for Los Osos, has been the Engineer of Record for $200+ million of innovative wastewater systems a number of which have involved installation of septic tank effluent collection systems in existing communities and design build-build-finance-operate, receiving engineering excellence awards, is the author of numerous USEPA Manuals on “Innovative Wastewater Management” and is a nationally recognized expert on decentralized wastewater systems. He has 35 years experience in decentralized wastewater management and his decentralized proposal for Los Osos is up for consideration by the County as a candidate for the Los Osos project. He can be reached at 866-964-2924, at This e-mail address is being protected from spambots. You need JavaScript enabled to view it , or through www.LombardoAssociates.com.