Rural reckoning: charting a flexible path for wastewater development

COVID-induced changes to companies’ work-from-home policies means many professional families that were once confined urban or suburban areas now have the freedom to consider a country home with a large yard and good internet. A recent survey by Paulsen Research out of Sioux Falls, South Dakota, indicated that of those respondents planning a move to rural America, 32% expected to purchase a property of less than 1 acre with a big yard, and a whopping 56% planned to purchase 1 to 5 acres. These migrants are not moving to rural America to farm, however. They are moving to have more space while still living close enough to the amenities and opportunities that a “microcity” offers.

The composition of rural migrant cohorts is also now trending younger than before. In addition to work-from-home policies, the rise of digital entrepreneurship is helping make that ideal rural lifestyle a viable option for those that are far from retirement. There is also demand across all age groups seeking more affordable rental housing, with more eyes looking beyond expensive metropolitan areas.

As Mark Smither of Paulsen Research remarked in an interview with American Equipment Manufacturers, “The idea [is] that where we live and where we work are now decoupled.” 

This phenomenon does not just affect those moving in from elsewhere. Rural leaders are daring to predict — rather than simply yearn — that their young people can build careers in the same communities in which they were raised.

Despite the prospects of a strengthening tax base, population inflection does not come without challenges, especially when that growth is likely to be lower density. Some states have hundreds of small communities without wastewater treatment systems that adequately protect environmental resources. Communities with decreasing or unpredictable tax revenue have deferred investment in traditional sewer solutions that would likely require unsustainable sewer rates for their citizens. 

Though prudent from a financial standpoint, this has left growing communities without the resources necessary to support an increasing population.

Fringe growth and planned developments can cause real headaches for utility planners. Who pays for the new sewer line extensions: existing long-term customers or as-yet-theoretical new arrivals? Will major roads be clogged during sewer construction? How much more biological load can the treatment plant handle before the community has to say no to the next permit application?

While a gravity sewer was the solution traditionally taught in 20^th-century engineering programs, solutions for wastewater collection have evolved to include more nimble options like liquid-only sewer and grinder systems, each considered a type of low-pressure sewer. 

A grinder system macerates both solids and liquids into a slurry to be pumped downstream. In contrast, liquid-only sewer uses an on-lot tank, which collects solids to take advantage of passive digestion and sends only the liquid portion downstream through small-diameter (typically 1.5- to 2-inch) collection lines.

The slope requirements of gravity construction make avoiding existing utility lines difficult, not to mention the headache of any inadvertent damage and repair. Avoiding utility conflicts increases design time for gravity sewers, whereas pressure sewers can easily be rerouted. Laying small-diameter pipe in the roadside right-of-way via shallow trenching or even directional boring means streets will not be torn up, avoiding prolonged traffic delays and expensive pavement reconstruction.

These low-pressure solutions also allow for unusual flexibility in siting the treatment plant. Instead of selecting a site at the lowest elevation to minimize expensive lift stations – as would traditionally be done for a gravity collection system – a pressure sewer enables directing flow up over a hill or to an alternate site outside of town. 

Liquid-only sewer allows for maximum flexibility in siting: with only the liquid portion of the waste stream traveling through collection lines, neighboring communities can combine their liquid-only sewer systems and pump to a common treatment plant miles away. Or, because a liquid-only sewer contributes only minimal biochemical oxygen demand (BOD), a neighboring community’s existing wastewater treatment plant could accept the additional hydraulic load without worrying about biological overload.

In outlying areas where aquifer recharge is a particular concern, liquid-only sewer and decentralized treatment allow for keeping the treated effluent in the neighborhoods where it is generated. Treated effluent can be reused for surface irrigation, car washing, or dust control prior to discharge (subject to local regulations). This also negates the energy required to send recovered water long distances from a water treatment plant.

As a bonus, the low biological loading from a liquid-only sewer makes it possible to choose a passive treatment option like packed-bed filters. These systems use simple controls and do not require a full-time operator to continuously monitor or adjust the system, as would be needed in a traditional treatment facility. Rather, small towns can utilize a part-time operator who already serves in another capacity, such as road maintenance personnel, to do periodic inspections and light maintenance. 

Full-time operators are hard to find — and keep — in today’s labor market. Operational costs tally not just from direct labor, but in the indirect costs to recruit or train a new operator; avoiding a highly complex treatment process lowers the risk of unavailable or unaffordable labor.

Completing a life-cycle cost analysis before making capital equipment investments is a critical step that utility planners literally cannot afford to skip. Equipment reliability, replacement rates, labor requirements for operation and maintenance, pump power costs, tank pumping intervals, mainline cleaning, air valve maintenance, and inflation scenarios all need to be factored into the equation. Before making a technology selection for their town, city officials should visit a comparable system — preferably one that has been in operation for at least 10 years — and ask about maintenance costs and hassles.

Life-cycle costs can differ widely by technology and by each local facility’s operational profile. A long-term (30- to 50-year), full life-cycle cost analysis can reshuffle the rank of suitable solutions. This timeframe is long enough to get a sense of equipment failure intervals, and any reputable manufacturer should be able to provide inquirers with this information.

Life-cycle cost considerations are especially important if the town will assume operation of the collection system after developers have sold the lots and relinquished their interest in a project. Even if a developer pays the up-front costs, the organization responsible for long-term operation is a valid stakeholder in the technology selection. Town leaders should always compare ongoing operation and maintenance (O&M) costs and future equipment repair and replacement (R&R) costs. Accounting for these costs will ensure that any rate structure implemented will fully fund all system costs after the system is operational and for the length of the system life. Rural planning can become deeply personal when generations of your neighbors will be affected by a town’s financial decisions. It is worth the time to slow down and complete the life-cycle cost assessment.

Utility planners often find themselves in the middle of town council discussions around controlled growth and expansion of city limits. A town’s autonomy to make decisions based on the needs and desires of the community, rather than just on affordability, is no small benefit to planners. If growth is desired, planners can extend a liquid-only sewer main to specific peripheral zones or require a developer to install a liquid-only sewer with its own neighborhood treatment plant. Liquid-only sewer is appropriate for both medium and low-density communities, as would commonly be found in rural America.

Once upon a time, rural areas’ economies were somewhat insulated from the economic fluctuations happening in metropolitan areas. With continued rural migration, economic connections are changing. Utility planners can be ready for whatever curveball is thrown next by taking advantage of flexible wastewater approaches, ultimately maintaining a clean environment and serving their rural communities.