When Sewage Is Discharged Into The Ground: What Goes, And What Stays

Wastewater treatments often consist of removing various "nutrients" from the waste. It is hard to think of wastewater as having nutrients when most people think of nutrients as something you have in your food or diet or something added to plant food. However, nutrients in wastewater are hardly different from those you consume or those in plant food. They are just extracted from an end source. Not only are certain nutrients extracted from the sewage, but then the liquid left is discharged to ground or surface water. Here is what goes into the ground and what stays behind as part of the extraction process. 

What Stays

The biological nutrient removal process takes phosphorus and nitrogen out of the waste. It does not remove one hundred percent of it because removing all of it will not benefit the soil into which the waste and remaining nutrients are leached/drained. The phosphorus and nitrogen that are extracted are removed to reduce toxic algae blooms and eutrophication, the over-saturation of nitrogen and phosphorus in the environment as a result of human "activities" and human waste. Waste treatment plants then recycle these nutrients, often selling them to fertilizer manufacturers. 

What Goes

After the water treatment plant removes the extra phosphorus and nitrogen, the holding tanks that still contain the remaining wastewater, minimal traces of nitrogen, and minimal traces of phosphorus are discharged out of the plant. They may either be discharged directly into the ground via an underground pipe system or into an open holding tank where it all evaporates into the air and then falls back down to earth the next time it rains and becomes part of the groundwater that way. This process is continuous, regardless of the volume of "clean" wastewater that the plant receives every hour and every day. 

Nature Recycles What Goes into the Ground

If the correct balance of nutrients is discharged from the water treatment facility, then nature takes care of the rest. The soil and the groundwater will recycle everything that comes into the ground and break it down so that it will not harm the environment. It is the same principle used in residential septic systems, except that the wastewater receives a few extra steps in the cleaning and purification process than the wastewater that is discharged from a residential septic system. If your industrial plant is looking for a similar biological nutrient removal solution, this process might be it.