Community Sewer Systems

The short answer is, “Yes.”

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 :

Aerial photo of an apartment complex with wastewater effluent drip field labeled to show size
Upon entering this apartment complex, you drive past the clubhouse and wind by a lush slope. Spoiler: it’s the wastewater drip field.

Here’s the satellite view for scale:

Satellite view of an apartment complex with wastewater drip field outlined.

If you’re making plans to develop property into apartments, give us a call. We can help you make the most of the space.

What is Eutrophication?

Eutrophication is plant overgrowth in domestic waterways.

green grass on water
Photo by cottonbro on Pexels.com

Wastewater contains nitrate and phosphorus which are nutrients that plants need to grow. Usually, nutrients are good things, but growing population density can result in too much of a good thing being deposited into streams, rivers, and other waterways. When this happens, plant life takes over – crowding out the habitats of fish and other aquatic life. As these plants die and rot, they can change water PH and bacterial levels.

To stop eutrophication, wastewater treatment systems need to greatly reduce or eliminate the amount of nitrate and phosphorus which they return to the watershed in their effluent. Governmental agencies set concentration maximums and enforce them through regular testing.

For the most part, nitrate and phosphorus can be reduced below regulatory thresholds through biological processes known as denitrification and mineralization. Advanced wastewater treatment systems use highly concentrated populations of beneficial bacteria to digest nitrate and phosphorus. The former is then released as nitrogen gas and the latter, collects in the tank as part of the sludge.

Even after advanced treatment, trace amounts of nitrate and phosphorus can frequently be found in wastewater effluent. Where mandated, further treatment can completely prevent even these from reaching the watershed.

If you’re in need of a wastewater system that will prevent eutrophication, let’s talk!

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.

An installer walking inside a wastewater system drip field dosing tank.
Every component in our systems must account for design criteria.

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:

An example design criteria table for wastewater system capacity in residential and commercial applications.
Design criteria differ based on locality.
  • 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.

Wastewater treatment uses natural biological processes to protect the environment from contaminants in sewage.

Wastewater poses several threats to the environment. Micro organisms which digest the suspended organic matter (Total Suspended Solids – TSS) in sewage use up the dissolved oxygen (DO) present in the water. The rate of this digestion can be measured as Carbonaceous Biological Oxygen Demand (CBOD). Water with high CBOD can deplete dissolved oxygen in waterways thereby suffocating wildlife.

septic tank cutaway
A common septic tank design

All wastewater treatment from septic tanks to municipal systems use gravity to settle out most solids. After settling, smaller organic particles remain suspended in the effluent. The settled wastewater then moves into biological treatment which increases the density of micro organisms in an oxygen rich environment. When done properly, biological treatment can neutralize the oxygen depleting effects of wastewater.

Wastewater treatment also removes chemical pollutants.

infographic of nitrification and denitrification in wastewater
Conversion of ammonia to nitrate and nitrate to nitrogen gas in wastewater.

One byproduct of human metabolism, ammonia, can poison watersheds through untreated sewage. Beneficial bacteria naturally occurring in wastewater use DO to convert toxic ammonia into the nutrient, nitrate. That’s good, but not quite good enough. When nitrate along with another nutrient, phosphorus, enters the environment, they can cause plant overgrowth that chokes waterways. Conveniently, other wastewater bacteria turn nitrate into nitrogen gas and mineralize phosphorus which settles out of the resulting effluent.

cutaway of an aerobic wastewater treatment plant
https://communitysewer.com/2020/12/16/biotank-overview/

These bacteria multiply into a slime layer called, “biofilm” in the biological reactor. Advanced treatment systems achieve high biofilm density by giving it a lot of surface area (media) to grow upon. The greater the surface area, the higher the treatment level.

Aqua Tech uses the latest in biofilm media technology to achieve maximum treatment in a very small treatment plant.

Wanna know more about wastewater or how we can take care of it for you?

What are the 3 Stages of Wastewater Treatment?

Wastewater can be treated in up to three stages generally known as primary, secondary, and tertiary treatment. Here’s what’s involved in each of these stages:

  • Primary Treatment

    In this stage, heavy solids and grease are separated from the raw sewage through gravity and buoyancy respectively. A conventional septic tank is an example of primary treatment.

  • Secondary Treatment

    The wastewater that leaves a septic tank or other primary treatment apparatus is still pretty contaminated with suspended solids and toxic chemicals such as ammonia. Secondary treatment systems use oxygen to facilitate natural digestion of contaminants by micro organisms already present in the wastewater. All municipal systems use secondary treatment.

  • Tertiary Treatment

    Even though much cleaner, water leaving secondary treatment can still pose somewhat of a threat to the environment. To ensure complete protection of aquifers and watersheds, wastewater effluent can enter a third treatment stage. Tertiary treatment usually involves some sort of natural or chemical filtration/sanitization. Examples of tertiary treatment are constructed wetlands or drip irrigation fields.

Our systems use all three stages of wastewater treatment to equip you for responsible growth. Let us show you how!

What does Advanced Wastewater Treatment involve?

Short answer:

“Advanced” doesn’t necessarily imply a particular type of technology so much as it refers to a degree of treatment. If the effluent leaving a system meets stringent criteria it’s said to have undergone advanced treatment.

Longer answer – Advanced treatment systems:

  • Use new technologies to accelerate biological consumption of organic contaminants in wastewater.
  • Remove toxic ammonia through nitrification.
  • Mitigate eutrophication of waterways by reducing nitrogen and phosphorus through Biological Nutrient Removal (BNR).
  • Sometimes introduce coagulants which settle nutrients and suspended solids through flocculation.
  • Occasionally feature chlorinators or UV arrays to sanitize effluent.
  • Rarely apply carbon filters to remove residual contaminants through adsorption.

Aqua Tech can design and build an advanced treatment system for nearly any situation.