Have you ever wondered where the wastewater from your homes goes? What happens to the liquid waste generated in our homes? Here in this guide, from Sintech, Leading wastewater pump exporter from India, we give you a step-by-step explanation of residential wastewater treatment and disposal.
Sources of Wastewater in Homes
Also known as liquid waste or sewage, wastewater in our homes are generated from the following sources:- Toilet flushing
- Bathroom and Kitchen Sinks
- Bathing
- General cleaning
Stage by Stage Treatment of Wastewater at the Treatment Centre
Stage One: Screening
This is the first stage of the process. It involves the removal of large suspended and floating objects in the water. Some common suspended solids include – sanitary napkins, diapers, face wipes, tissues, cotton buds, rags, bottle covers, bits of plastic and more. Removing these large objects is crucial, as these objects can damage the specialized equipment in the later stages.
Besides using filters to remove large objects, specialized equipment is then used to eliminate the grit that reaches the sewer.
Stage Two: Primary Treatment
The second step involves the separation of solid organic matter (usually human waste) from the sewage. The wastewater is passed through large settlement tanks. The solids then sink to the bottom of the tank. These solids that settle at the bottom of the tank are known as sludge.
The massive settlement tanks have big scrappers that continually rotate scraping the floor of the container. This causes the sludge to be pushed towards the center of the tank. The slurry is then pumped out of these tanks using large motors.
Once sludge is cleared from the wastewater, the remaining water is passed to the next stage for treatment.
Stage Three: Secondary Treatment
The water from Stage Two is passed through large rectangular tanks. These tanks are known as aeration lanes. Here, in this stage, the air is passed into the wastewater. It causes the growth of bacteria that breaks down any remaining sludge that escaped the previous step.
Stage Four: Final Treatment
This is the final step of residential wastewater treatment process. The wastewater free of sludge is passed once again into a settlement tank. Any remaining slurry settles at the bottom of the tank. As in stage two, it’s once again scraped and collected for treatment. The water at this stage is free from any residual chemicals and other harmful substances.
The water is then passed through a layer of sand to remove any additional particles. Finally, the clear water is let into nearby rivers or lakes, or into aquifers for recharging the groundwater system.
*Note that the stages may vary from one treatment plant to another, depending on the quantity of wastewater generated. However, the principle remains the same.
What about Industrial Wastewater Treatment?
Industries generate wastewater from various processes. Industrial wastewater treatment is the process of separating and removing contaminants from wastewater (commonly known as effluent). Some of the common pollutants in effluents include dissolved heavy metals, oils, organic compounds, and other suspended solids. Industrial wastewater treatment involves three phases:Phase 1: Pre-Treatment
Pre-treatment consists of the removal of free oils, soluble oils, gross contaminants, and debris. Let’s take a closer look at how each of these contaminants is removed.
Oil – Soluble and Free Oil
Oils must be removed from the waste stream before it goes for chemical treatment. Some of the types of equipment used in this stage include:- Wheel skimmers
- Traditional belt skimmers
- Coalescers
Debris and Gross Contaminants
It contains large solids that are suspended in the waste stream. Settlement and filtration are the two most common methods employed to remove large contaminants from the wastewater.Soluble Metals, Phosphates, and Other Contaminants
Chemical precipitation is the method employed to remove these contaminants. The precipitants used depends on the chemicals present in the wastewater stream.Phase 2: Chemical Treatment
Solids that are lesser than 200 microns cannot be filtered out using Phase 1. Hence, wastewater requires further chemical treatment to remove these tiny substances. The processes involved are:
- Reactant powder chemistry
- Emulsions
- Micron filters
Phase 3: Post-Treatment
Post-treatment refers to the process of polishing or cleaning water. Some of the chemicals employed at this stage include – alcohol, glycol or charcoal to effectively remove any impurities from water. Other chemicals used include:
- Detergents and soaps
- Ammonia
- Fragrance inhibitors
- Chemical oxygenator and more