Wastewater can be treated without the use of chemicals through physical and biological processes. Physical methods include screening, sedimentation, filtration, and aeration. Biological methods involve using microorganisms to break down organic matter. Natural systems like constructed wetlands also offer a chemical-free approach to wastewater treatment.
Physical Treatment Methods:
- Screening:
Wastewater is passed through screens to remove large debris like plastics, rags, and sticks.
- Sedimentation:
In settling tanks, heavier solid particles settle to the bottom, separating from the water. This process can be enhanced by adding flocculants, but these are not always necessary.
- Filtration:
Wastewater is passed through filters (e.g., sand filters) to remove smaller suspended solids.
- Aeration:
Air is bubbled through the water to encourage the growth of aerobic bacteria that break down organic matter.
- Skimming:
Oils, grease, and other floatable materials are removed from the surface.
Biological Treatment Methods:
- Activated Sludge Process:
Aerobic bacteria break down organic matter in wastewater, forming a sludge that can be removed by settling.
- Anaerobic Digestion:
In the absence of oxygen, anaerobic bacteria break down organic matter, producing biogas (methane) and a nutrient-rich sludge.
- Constructed Wetlands:
These systems use natural processes involving plants and microorganisms to filter and treat wastewater.
Natural Treatment Systems:
- Soil Aquifers:
Wastewater can be infiltrated into the ground, where soil acts as a natural filter, removing pollutants.
- Slow Rate Irrigation:
Wastewater is applied to land at a controlled rate, allowing natural processes to purify the water.
- Aquaculture:
Aquatic plants and animals can be used to treat wastewater, similar to constructed wetlands.
Other Considerations:
- Membrane Bioreactors (MBRs): These combine biological treatment with membrane filtration, producing high-quality effluent.
- Reverse Osmosis (RO): While RO uses membranes, it can be part of a chemical-free system if the membranes are designed to handle the wastewater's specific characteristics.
UV Disinfection: UV light can be used to kill pathogens without adding chemicals.
After a first settling and/or screening treatment, wastewaters (grey) to be treated (civil, industrial, domestic) are pumped into equipment modules.
By the wastewaters contact, plastic carriers are covered by a bacterial biological film. Bacteria are nourished by the organic substance dissolved into the water, purifying it.
Purified waters can be released in water bodies without harming water bodies or on the ground.
A stainless-steel cell, full of plastic carriers of different dimension, slowly rotates partially submerged inside a tank, where there are wastewaters to be purified. Plastic carriers spontaneously form a bacterial film that progressively presents, at first, heterotrophic bacteria development which are able to nourish of organic carbon pollutants; then the decrease of COD and BOD concentration and then the development of autotrophic bacteria. They belong to the nitrosomonas and nitrobacter category and they are able to oxidize ammonium, transforming it into nitrites and nitrates. The cell containing the carriers can be flooded as needed; in this way the depuration process control is obtained and it can be oriented both to the carbon removal and wastewaters denitrification.
These plants, do not need any blower for the bacteria film oxygenation. It's the slow reactor rotation – alternatively submerged into sewage and into atmosphere – to guarantee the adequate oxygen supply for the oxidation aerobically of the sewage made by the biological film attached to the carriers. In this way it is possible to obtain a huge reduction of functioning and operating treatment costs.