February 2008, Vol. 20, No.2
Distributed Wastewater Management
A practical, cost-effective, and sustainable approach to solving wastewater problems
The term distributed wastewater management is gaining widespread use by wastewater professionals. That’s because it defines a practical extension to mainstream master planning, taking into account current economic, social, and environmental realities. Gone are the big U.S. Environmental Protection Agency grants that paid for major interceptors, pumping stations, force mains, and regional treatment facilities. Gone are the days when we ignored the inconvenience to the public associated with tearing up roads for major collection system improvements. Gone are the days when we looked only at the effluent quality of wastewater treatment and not at the costs with respect to greenhouse gas emissions from treatment processes and their power plant energy demands. Most importantly, gone are the days when we ignored the fundamental value of reclaimed water.
Simply put, distributed wastewater management is the oversight of several wastewater collection, treatment, and discharge systems by a single responsible entity. This definition is inclusive. The most important aspect of the definition is that a single entity is managing multiple systems. The intent of distributed wastewater management is for utilities and their supporting entities (such as consultants) to approach the planning effort for a specific service area without the forgone conclusion that regionalization or centralization of treatment facilities is the best alternative.
A holistic understanding of needs, costs, and benefits must be determined prior to and during the planning effort. For example, an existing collection system may be experiencing capacity issues attributed to growth. Pipe bursting or a parallel pipe and possibly an expansion at the central wastewater treatment plant might not be the most appropriate alternative. A satellite facility might be best because there is an identified need for reclaimed water for irrigation, cooling water, stream augmentation, or aquifer recharge. Or, say a new rural subdivision is planned in a low-density part of the service area. It may be more cost-effective to install a community-based wastewater treatment system that provides pretreatment prior to final soil treatment rather than to install a long interceptor that pipes the waste back to the central system. All aspects of cost should be included in making this determination: labor, power, chemicals, materials (including capital reserves), and debt service.
In some parts of the county, different groups maintain their own systems. For instance, the school system has operators who run the school’s water and wastewater systems. The parks and recreation department has operators who run its water and wastewater systems. An authority provides service to citizens in the unincorporated portions of the county. The towns provide service to their citizens.
This is the situation in Loudoun County, Va., a suburb of Washington, D.C. Loudoun County Sanitation Authority (LCSA) provides water and wastewater service to the unincorporated portions of the county and currently serves approximately 53,000 customers. The policy of the Loudoun County Board of Supervisors is that water and wastewater service may be provided only by onsite or community systems in the rural areas of the county. LCSA owns and operates the community systems and currently serves approximately 1000 customers in this manner.
Recently, LCSA has been approached by the school system, the parks and recreation department, and some of the towns to operate their water and wastewater facilities, either on a contract basis or eventually to take over ownership of these systems. The primary reasoning is that LCSA has the expertise and ability to manage these systems; adheres to regulations and interacts with regulators; consistently employs sufficient staff to cover weekday, weekend, and emergency operations adequately; and has its sole focus on water and wastewater treatment service, rather than on other areas, such as education or recreation. Half of the distributed water and wastewater facilities LCSA operates are owned by other entities that would rather focus on their primary business area (such as education, recreation, or commercial activities) and contract with LCSA to provide water and wastewater services.
The net effect of these contract operations has reduced the number of system violations to near zero because LCSA understands the details of the permits and knows how to manage these facilities competently. The owner entities can focus on their primary responsibilities of providing higher levels of service, and costs are about the same because the perceived additional costs of outsourcing these services are reduced due to economies of scale that LCSA realizes. The owner entities do not have to worry about the administrative headache of staffing and managing facilities that they do not understand well. LCSA is performing timely maintenance, rather than letting the repairs languish, as happened in the past.
Distributed wastewater management is a subset of distributed water management, which includes drinking water, wastewater, reclaimed water (if differentiated), and stormwater. In the example above, LCSA provides water and wastewater services and soon will provide reclaimed-water services. LCSA staff are licensed as both water and wastewater operators. This provides an economy with respect to operations, as well as minimizing overhead. Adding reclaimed-water treatment and distribution responsibilities within one management entity is a natural extension. Stormwater services also would make sense. Grouping stormwater with wastewater is applicable when total maximum daily loads identify problems from discharges of both point and nonpoint sources. Entities that are responsible for both would have more ability to most effectively dedicate resources toward reducing contributions to local waterbodies while minimizing impacts to customers.
As costs associated with wastewater management continue to rise — whether from additional treatment requirements, increasing energy costs, or growing repair and replacement expenses — the distributed wastewater management approach is receiving increased attention. All it requires is a shift in mindset from centralization of facilities to centralization of management and resources. In today’s knowledge-based economy, this is not a difficult shift. The biggest obstacle is that reliable cost data are not abundantly available, and many professionals must become more familiar with distributed approaches to appropriately consider and evaluate the full set of options available. Research organizations, such as the Water Environment Research Foundation (Alexandria, Va.) and others, are attempting to address these issues. The most important thing for utilities and consultants to do now is openly and accurately consider all alternatives when assessing service options.
Distributed wastewater management enables utilities to consider economic, social, and environmental aspects of providing wastewater service and to select the most appropriate service solutions from a larger “toolbox” of options. As utilities become more and more conscious of sustainability — be it with respect to climate change or availability of water resources —distributed wastewater (and holistic water) management is a philosophy more utilities are embracing.
Todd Danielson is manager of community systems at the Loudoun County Sanitation Authority (Leesburg, Va.) and a member of the Water Environment Federation (Alexandria, Va.) Small Communities Committee.