WATER + STORMWATER
A large low-pressure pipe dispersal system is used to distribute wastewater to the soil close to the point of origin for a subdivision.
Decentralized collection, treatment, and dispersal advances solve community challenges. By Allison Blodig, REHS Wastewater management tools
Pre-engineered, decentralized treatment systems provide long-term treatment solutions at an affordable cost; however, they do require engineers and regulators to be comfortable with how these Alternative Onsite Wastewater Treatment Systems (AOWTS) have been designed and sized by the manufacturers. If they are accustomed to designing, engineering, and incorporating individual components to make up a centralized treatment system, this approach saves time and money that would normally go into the design/engineering phase of the treatment. Engineers who are embracing these new options are finding they can easily be adapted to various site conditions and that these space-saving and flexible technologies do work well when applied appropriately, in- stalled correctly, and maintained consistently. This flexibility can lend itself whether designing and installing individual AOWTS, several smaller-scale satellite AOWTS, or a single larger AWOTS to serve the needs of treating the wastewater in a development. Successful nutrient removal Although not always attributed to onsite septic systems, nitrogen can be a problem in coastal estuaries throughout the United States includ- ing Cape Cod, Long Island Sound, New Jersey, Delaware, Chesapeake Bay, and Puget Sound. While tides, currents, or fresh water naturally flush estuaries, nitrogen can accumulate in highly populated coastal areas or those with extensive agricultural runoff when the estuaries don’t flush adequately. Nitrogen pollution issues have been catalyzing initiatives to develop new ways of treating wastewater at individual sites as well as com- munity and municipal systems. AOWTS have been used successfully to replace or rehabilitate outdated onsite systems such as cesspools and eliminate surface discharge. Finding less capital-intensive solutions that can extend the life and ex- pand the capacity of existing centralized systems is also a high priority in many communities that have aging or undersized wastewater treat- ment plants but are open to smart sustainable development. AOWTS are often paired with a range of updated components and new disposal field products such as plastic chambers, geosynthetic aggregate bun- dles, and large, plastic septic tanks. This increases the opportunity to protect natural resources and public health at a cost that communities can afford.
For communities with no access to centralized wastewater treatment, finding cost-effective and sustainable solutions for residential and commercial treatment and dispersal/disposal is a challenge. The need for high-level treatment strategies that address nitrogen reduction, wa- tershed protection, and sensitive environments has catalyzed the design of advanced treatment systems to solve these issues. This is mostly due to the high cost of traditional centralized wastewater collection and treatment and the innovation with small-scale treatment systems. To sustain the environment and community health, engineers, mu- nicipal health officials, and regulators are adding to their wastewater solutions tool chest the use of pre-engineered, decentralized treatment systems as well as incorporating nontraditional collection methods and soil dispersal for final disposal. Where individual onsite septic systems are the norm, town officials have a host of traditional and advanced decentralized treatment system possibilities to protect local waterways and water supplies, upgrade outdated systems to reduce nitrogen loading, and improve overall wastewater management for the community. Because of the advances in collection, treatment, and dispersal, decentralized systems are no longer limited to small-flow systems and those in remote locations. Some decentralized communities are collecting and treating wastewa- ter in excess of 3.75 million liters per day. It’s a boost to rural and growing communities that the wastewater technologies and solutions available for large-scale decentralized systems are now available for small-scale systems as well. Communities, homeowners, and develop- ers can move ahead with projects without waiting for a sewer extension to reach their site or the treatment plant to be expanded.
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csengineermag.com
january 2018
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