toxicity evaluation of septic tank overflow water

[Prometeo]

HI, I'm considering where to drain the overflow water of septic tank. I have a 1500 gallon septic tank which drains the overflow water, into a second concrete sump, of 200 gallons, and then I'm actually evaluating. The point is: how toxic is this water? Theoretically soaps are toxic only due to their original pH, after that they are not so very polluting? Are they just salts I wonder

 

[peakbagger]

There are two types of liquid processed by conventional septic systems. "gray water" and "black water" Gray water is sink, shower and wash water. It can have varying degrees of Biological Oxygen Demand (BOD) Some jurisdictions allow reuse for non potable purposes like watering gardens (and lawns) usually after physical seperation of solids. Black waste is usually human waste, in rare occasions urine can go to its own treatment system as its sterile, its got a lot of urea in it and some people use it to inoculate biochar with it. Solid human waste and the liquid in contact with it has to go through either an aerobic or anerobic process to kill the pathogens.

In a conventional septic tank there is not a lot of biology going on, it mostly a settling basin although some anerobic activity may be occurring. Most of the biology is going on in the leach field in particular at the interface between the soil and the drainage laterals. An aerobic biological mat is formed at these interfaces and develop a colony of bacteria that is optimized to treat the waste. The liquid leaving the field usually is biologically "clean" but in many places, nitrates (salts) will get carried into the soil. They are an issue in areas with lots of septic systems are located. Adding nitrate removal is quite expensive. Also seeping out into the soil are complex compounds like pharmaceuticals that are either directly dumped in the sewer or indirectly introduced. PFAS chemicals will also pass in addition to siloxane compounds that are used ion many personal grooming products. The quantities are quite small and with a large piece of property they may not cycle up enough to ever be an issue but they do not disappear.

If you are proposing disposing of wastewater that has been physically separated in a primary septic tank but it has not gone through either aerobic or anerobic treatment, then there is no good place to put it iother than further treatment. There are many advanced systems out there may be doing anerobic or aerobic treatment in secondary tank so its very much system dependent. I have seen very expensive high end units that are basically a mini wastewater system in box and the water leaving them is very impressive but usually still got the non biological contaminants unless they run it through a carbon system or reverse osmosis.

 

[Prometeo]

Thanks @peakbagger
great information,
I spoke with the municipality and there are no big demands,
I won't have to eliminate nitrates/phosphates
but good oxidation,
it's my standard,
what I'm aiming for,
this overflow water will go into a small area with oak trees,
basically I don't want them to die,
but who possibly benefit from it.

 

[EatenByLimestone]

Careful with roots in drain fields. Roots and pipes in general can cause lots of problems.

 

[Prometeo]

Careful with roots in drain fields. Roots and pipes in general can cause lots of problems.

Thank you, something I hadn't taken into consideration

 

[Prometeo]

the first step of oxidation of overflow water will consist of conveying it in this pipe, approximately 50 feet, many bacteria should form on the walls, reducing pollutants, will do something?

 

[EatenByLimestone]

Sure it will. It’ll turn all nitrogen in your water to nitrate. You’ll need anaerobic bacteria to convert that.

 

[Prometeo]

Sure it will. It’ll turn all nitrogen in your water to nitrate. You’ll need anaerobic bacteria to convert that.

Very well, thank you! If I'm not wrong, in this concrete pit the oxygen should not be too much, without oxygenation systems. The outgoing water will have a closing damper, to modulate the flow rate, the idea is that it must come out more slowly than what comes in. The exit hole will be approximately 2 thirds of the way up, the remainder will be considered as expansion, this should further favor anaerobic bacteria, perhaps

 

[EatenByLimestone]

Maybe.

 

[semipro]

The quality of the wastewater leaving your house is largely dependent on what you flush down your toilets and drains, including that from laundry washing. I'd be most concerned about chemicals other than soaps like cleaning products, fragrances, laundry additives, and pharmaceuticals. Cancer treatment drugs, especially, can be quite toxic. Even industrial solvents like trichloroethylene (TCE) have been used in septic systems to clean fats from pipes.

Discharge of liquids to wooded areas is commonly done here using drip irrigation systems rather than leach fields. These are typically aerobic treatment systems that include air fans, effluent storage tanks, and pump systems for drip discharge.

 

[stoveliker]

Also think about micro plastics from e.g. laundry or dishwasher pods. They claim it's dissolvable plastic, but it simply breaks down in micro plastics.
I would not want to be polluting my own yard with micro plastics; enough coming in from elsewhere as it is.

 

[zrock]

this used to be common practice when i was a kid.. ours used to over flow to the ditch in front of the house.

 

[Prometeo]

the system is ready registered trademark ® of course 😂

 

[EatenByLimestone]

May it handle all the crap you throw at it!

 

[Prometeo]

it will only process the overflow, filtered water