C+S April 2021 Vol. 7 Issue 4 (web)

Some examples of assessment factors that will impact the decision- making process are: • A wastewater treatment plant which is projected to, or routinely, receives flows in excess of the rated capacity due to combined sewer overflows (CSOs) during precipitation events (less tolerance for these events than in the past) • Watershed proximity issues including groundwater pollution and saltwater intrusion for coastal communities • Regulatory noncompliance of current facilities or individual residen- tial systems within the community Deliberately access the treatment technology options. Do not force a solution or settle on a product for your project until all the boundary conditions are known. These include design criteria, site location, size of site, discharge limits, etc. There is no one product to fit all projects, the design engineer is best served by remaining neutral to the system type, keeping all options open so the client can be best served. Any design choice must meet the treatment discharge limits, account for O&M and the skill level of the operators, address O&M costs, consider product lifespan, and bottom-line overall costs for the treatment plant and construction. Build professional management into any large wastewater treat- ment system design. Recognizing the need to advocate advanced wastewater treatment systems of a scale that will support positive development, health of- ficials also recognize and often require these systems to be profession- ally managed. Professional management provides more control on the quality of the waste treatment process. If competent management is available, then utilities may favor this approach as the most cost- effective long-term solution. Large-scale Treatment System Options Consider Advanced Onsite Wastewater Treatment Systems (AOWTS). AOWTS high-level treatment strategies and systemdesigns that address nitrogen reduction, watershed protection, and sensitive en- vironments are particularly critical for coastal communities and those

where dispersal to surface waters is no longer an option. Engineers who are embracing these new options find them easily adaptable to various site conditions. Pre-engineered, Alternative Onsite Wastewater Treatment Systems (AOWTS) provide long-term treatment solutions and professional management in many cases. What’s great is that they can be used in multiple small scale or single larger system applications. Explore a combination of centralized and decentralized wastewater treatment technologies Engineers are commonly challenged to design wastewater treatment so- lutions for communities faced with environmental challenges including CSOs from outdated centralized systems. Often these same communities have limited, if any, budget for infrastructure improvements. In these instances, taking a combined approach that utilizes both centralized and decentralized methodology can be an option to review. For example, by expanding the wastewater district service area without extending the collection system out to new distant parcels the district can incorporate decentralized strategies by installing a satellite plant with subsurface disposal. These systems often provide collection that moves to a centralized treatment facility then to a large disposal field. STEP systems, for individual homes or businesses can collect effluent in tanks and pump to a centralized treatment facility. Utilizing decen- tralized treatment strategies in concert with centralized wastewater districts or management structures offers the optimum solution for communities with minimum budgets for infrastructure projects and growing treatment needs. This centralized/decentralized strategy and combining of technolo- gies also can work well with large commercial systems with multiple wastewater generating sources. Large businesses and communities no longer need wait or pay exorbitant tap fees to tie-in to existing central- ized services. Consultants will perform feasibility studies reviewing options for their clients, and the decentralized solution may yield the most beneficial cost position. In the case of community wastewater treatment facilities that are reach- ing or over capacity, adding a bed utilizing subsurface infiltration, such


April 2021


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