Most states in the US publish design flow charts to stipulate the capacity of wastewater systems. Here’s a list of residential and commercial design flow charts for new construction organized by state.
These documents have been downloaded from various regulatory agencies. Jurisdictions for any particular job will vary. Aqua Tech makes no certifications regarding the veracity, applicability, or relevance of the documents listed below.
Contact us for more on how to plan the wastewater component of your particular project:
So, you’ve got that piece of land and you’re ready to start developing. Here are some things you might need to know about RV park sewer systems.
1. RV park sewer systems have a big job.
RV’s are made to use less water. That’s great! Unless you have to treat their waste. Less water means less dilution. Less dilution means higher strength wastewater.
Wastewater strength is commonly measured in biological oxygen demand (BOD). That’s the amount of oxygen it is take out of the environment for biological processes. Household wastewater contains around 250 mg/L BOD. The raw influent entering an RV sewer system can be as high in BOD as 1000 mg/L.
Since septic tanks only reduce BOD by 30% RV parks discharge up to 700 mg/L BOD into their drain fields. That’s a lot of pollution entering the environment and potentially into the aquifer.
Aqua Tech wastewater treatment systems remove pollutants from RV wastewater before its discharged to the environment. We can take that 1000 mg/L RV raw influent down under 10 mg/L. That’s better than most municipal systems.
2. RV park wastewater systems probably need a discharge permit.
In most states wastewater flows beyond that which is produced by a large single-family home must be permitted through an environmental protection agency. You will likely need a state-licensed engineer to write the permit. If you don’t have an engineer, we can probably refer one to you. Just give us a call.
As part of the permitting process, the engineer will determine influent parameters based on samples taken from the actual flow for a current RV park or based on modeling assumptions provided by the state. The engineer will also determine effluent limits based on regulatory guidance for the location and discharge type.
Once they have collected the data, they’ll send us the design criteria and we’ll design a system to meet them.
They’re too expensive for a couple of reasons. First, the sewerage to get the wastewater from the RV sites to the wastewater treatment plant costs too much. Gravity sewers often require high-diameter pipe, manhole covers, wet wells, and lift stations. All that can up to hundreds of thousands of dollars spent before you welcome your first guest. Aqua Tech sells STEP Collection systems as a modular, low-cost alternative to gravity collection systems. Since RV design flow can be considerably lower than residential flows, developers can often get up to 4 sites on one STEP system.
The second reason wastewater systems are too expensive is the approach most vendors take to designing and deploying RV sewer systems. Many wastewater treatment system providers produce one-size-fits-all systems that don’t actually fit your needs. The high overhead and material cost of these systems can kill the ROI on your development.
We frequently recommend subsurface drip disposal (SDD) systems to dispose of treated RV park wastewater. SDD systems discharge nutrified water to a grass crop under low pressure. This means you can use the greenspace around your RV park for your disposal field.
Our systems can treat RV park wastewater to surface water discharge standards. By removing most residual nutrients and contaminants our systems can safely dispose sewer water to a stream, river, or lake.
There are lots of other disposal options that your engineer might recommend. We can work with them to make sure the effluent will meets compliance requirements for whatever works best.
For some of our RV Park projects, check out our portfolio.
One of the first questions we get asked, is “How much does a sewage treatment plant cost?” That’s a reasonable question. And we love answering it! That’s because our top-quality systems are also some of the least expensive on the market. Don’t believe us? Click the button below to get an estimate for your particular project and then shop around.
Every Aqua Tech system is custom designed around each project. Our sewage treatment plants must meet local design standards while serving the particularities of each application. Factors such as collection type, design flow, and disposal method all play into the system design. And the system design determines the price.
In asking, “How much does a sewage treatment plant cost,” it’s important to remember that size matters.
Wastewater treatment systems, like a lot of other products, are subject to the economy of scale. Price per gallon goes down as the system size goes up.
Like in the diagram, the effect is more pronounced as the system size gets smaller. A 2000 gallon per day system might cost 3x as much per gallon as a 20,000 gallon per day system which might cost 30% more per gallon than a 40,000 gallon per day system.
The economy of scale in this case means that smaller systems require the same planning, design, construction, installation and startup time as do the larger systems. So, if you ask, “How much does a sewage treatment plant cost?” We’ll first need to know, “How big?”
It’s also important to remember that not all sewage is created equal.
Commercial wastewater is typically higher strength than what comes out of your home. RV Parks, for instance can produce raw sewage with a BOD (biological oxygen demand) of nearly 1000 mg/L while concentrations in residential wastewater average around 250 mg/L. Higher strength wastewater requires more biofilm media, larger bioreactors, and bigger tanks to reach mandated effluent limits.
Location (location, location) affects wastewater system price.
Several local conditions such as fast perc rates, high water tables, high quality, or impaired waterways call for stringent treatment levels even for subsurface disposal.
The Chesapeake Bay for instance, has been designated by the EPA as an impaired waterway. That means wastewater discharge in its watershed must be treated to municipal wastewater treatment standards or better.
This is a process flow diagram for a system to be installed in the Chesapeake Bay Watershed. It requires special appurtenances (add-ons) to ensure reduction of total nitrogen to under 2.5 mg/L.
That’s a heckuva lot of reduction for a system discharging subsurface.
Sometimes location affects the way treated effluent must be disposed.
The soil in the eastern two-third of Texas, for instance, absorbs very poorly. TCEQ (Texas Commision on Environmental Quality) consequently mandates a soil application rate (SAR) of no more than .1 gallons per square foot per day for subsurface drip disposal systems. That means drip disposal outside the crosshatched counties on this map can cost three times as much as the national average.
Disposal method affects how much a sewage treatment plant will cost.
Aqua Tech’s wastewater treatment technology is so advanced that we also sell surface water discharge systems. With surface water discharge you can do away with a disposal system altogether. That means the system will need to treat to a higher level and include disinfection. But even with those additions, surface water discharge systems price out around 10% less than subsurface disposal systems in most cases.
Getting there can be half the savings.
The cost of a sewage treatment plant is only part of the overall cost of developing your sewer infrastructure. Sanitary sewers needed to convey the wastewater to the system can cost significantly more than the treatment and disposal systems together. Many Aqua Tech customers have found they can save a ton of money up front and over the long run with STEP Collection. And because STEP Collection eliminates the need for a large settling tank at the treatment works, it can save you money on the treatment system as well.
There’s no fast way to accurately answer, “How much does a sewage treatment plant cost.”
But we don’t mind doing the work to put a free estimate together. Just fill out and submit this form!
However, it’s not very common. While several apartment units might share a single large septic tank, they still each need enough lateral lines to treat their effluent. So, a single apartment building would need several acres of leach field. An apartment complex would need to devote over half the land to wastewater treatment.
Advanced wastewater systems are a better option for apartments outside the reach of sanitary sewers. Because they treat septic effluent in a biological reactor rather than in the ground, they can reduce the acreage needed for disposal.
Here’s an example of apartment complex wastewater treatment that works :
Here’s the satellite view for scale:
If you’re making plans to develop property into apartments, give us a call. We can help you make the most of the space.
Wastewater systems in the US are sized based on the maximum number of gallons per day they can treat.
A 300-room hotel, for instance, might require a 50,000 gallon-per-day system. Depending on soil loading rate*, that system might need a 2 acre drip field for effluent disposal.
Here are some factors that determine how many gallons per day your community septic or other wastewater system must be able to handle:
Capacity in gallons per day is determined by state and local design specifications.
These regulatory agencies calculate required treatment capacity in terms of maximum gallons used per person per day or maximum flow per bedroom per day, etc.
Commercial wastewater systems use more complex formulas that take their specific usage into account. The hotel mentioned above might need to account for 75 gallons per bed per day but might also have a restaurant and a bar attached for which another 12 gallons per seat per meal would have to be added.
Design criteria must also assume the level of pollution present within wastewater from different sources. Very dirty wastewater takes longer to treat which means systems must have higher capacity than what is released to give the system the time needed.
Here is an example of a design criteria matrix from an actual state regulatory agency:
Design criteria tables such as the one above provide a starting point to determine size, but in most cases, regulatory agencies grant variances based on actual flow and treatment level.
We at Aqua Tech will research the design criteria required for your project and budget around them. As the build gets closer, we reevaluate your treatment needs and work with civil engineers and regulatory authorities to ensure regulatory compliance without excess expense.
Bottom line: Use this table to get a rough estimate. When you’re ready, let’s talk and get more specific.
*Soils differ in how much moisture they can absorb per hour. Very dense soil might only be able to absorb one tenth of a gallon per square foot every hour while porous soil can absorb almost a full gallon per square foot. Soil absorption per hour is called its “loading rate.” The higher the loading rate the smaller the drip field needed.
Several places around the US are currently experiencing a construction boom and we’re delighted to be a part of it. Here’s a mixed use system that our engineers have just designed.
This particular system was designed to treat residential and commercial wastewater at the same time. Notice that the effluent (outflow) discharges at ground level. This is a septic system with no leach field!
Here’s the secret:
This private wastewater treatment plant removes nearly all of the Biological Oxygen Demand (BOD), Total Suspended Solids (TSS), and Total Nitrogen (TN).