Water is one of the most precious commodities available to humans worldwide. Water is used on a day to day basis by everyone for different purposes such as bathing, cleaning, cooking, etc. But have you ever thought about where the water ends up and what happens with the used water in the future?
Many people don’t believe this concerns them but it should as it has a detrimental effect to our environment which affects them in the long-term through global warming. Therefore, if we start contemplating the wastewater treatment and understand how it works then you may just think twice and cut down on the time you spend in your next shower in order to save water. Before we explain the process from the start to the finish let’s first clear out a few basic definitions.
What is Wastewater ?
Wastewater is used water which has originated from domestic, industrial, agricultural, medical or transport industries. The used water transforms into wastewater depending upon the change of its quality, composition and/or temperature. However, wastewater doesn’t include water which is released from ponds or reservoirs for fish farming.
Types of Wastewater
We can split wastewater into three main groups, based on where it comes from:
Sewage Water: All the wastewater which is used in domestic dwellings or households which originate from toilets, sinks or showers.
Industrial Wastewater: water which originates from production, industrial and commercial activities and it has a different chemical composition compared to sewage water
Municipal Wastewater: This is a combination of sewage water, industrial wastewater, and rainwater that runs off city streets into public sewers.
Process of Working Municipal Wastewater Treatment
The treatment of municipal wastewater involves several key steps to make water safe to release or reuse. Here’s how a typical municipal wastewater treatment plant operates:
Draining Wastewater
The first step is to drain the wastewater to the WWTP by gravity through the main sewer system.
Preliminary Treatment or Pre-Treatment
The first mechanical stage is called the preliminary treatment or rather the pre-treatment in which water flows through a gravel chamber separating out the grit from the water. The gravel which is collected is then disposed of at the dump.
Bar Screens
Water then goes further down and reaches the bar screens which are used to remove larger objects from the wastewater. At first come the coarse screens and then the fine screens which remove smaller objects such as matches, cigarette butts, or undigested foods.
Grit Removal
Once the large objects are removed, then the grit is removed from the wastewater. Similar to the gravel chamber, the grit chamber allows the settlement of grit. The grit is then removed from the tank and disposed of at the dump. Neither gravel nor grit can be reused as both are highly contaminated.
Primary Treatment
The next sedimentation stage is known as primary treatment in which the wastewater flows to the “pre-settling basins” also known as primary settling tanks. Over here the water is driven towards the hopper in the base of the tank. A hopper arm moves around the edge of the tank at an approximate velocity of 4 cm/s. This is the point where primary pre-treatment ends and secondary wastewater treatment begins. The levels of wastewater pollution drop to 60% after the primary treatment is finished.
Secondary Treatment or Biological Stage
The secondary treatment which is also called the biological stage then begins. WWTPs use bacteria which consume the contaminants, in particular biodegradable organics, carbon, and phosphorus. The dead bacteria and organic residue eventually transform into sludge.
Excess Sludge Removal
During the biological process stage, the excess sludge (i.e., excess bacteria) is pumped out and transported before the settling tanks. Over here, the sludge-like substance settles and is moved to the digestion tanks for further treatment.
Sludge Digestion
In these digestion tanks, sludge is pumped out of the settling tanks to become heated and mixed. Afterwards, biogas is produced during the digestion process from the sludge which the WWTPs can reuse, for instance for thermal and electrical energy production uses.
Second Digestion Stage
When the sludge digestion reaches optimal level, the second digestion stage takes place in the storage tanks. Over here the water is separated from the semi-solid sludge and transported back for further treatment, whereas the residual semi-solid undergoes mechanical dewatering.
Final Sludge Processing
The sludge is then digested and dewatered to the optimal degree and is finally disposed of at the dump. After about one month, the sludge is sufficiently dried out and becomes ripe. If this final product complies with agricultural standards, then it can be reused for fertilisation of industrial crops.
Inspection of Service Water
The last and final step of wastewater treatment is the rigorous inspection of service water. The main goal of this inspection is to analyse the contamination level and make sure that the treated water is in compliance with the highest of standards which will define its release or reuse for domestic and/or industrial purposes.
Do wastewater treatment processes exist in India?
The answer is Yes, here in India, the demand for effective wastewater treatment is increasing due to rapid industrialization and urbanization. Wastewater treatment is definitely a tough process with a significant goal which requires a lot of expertise and hard work. If you are interested in wastewater treatment or need guidance then Permionics is the best solution for you. Permionics has been the pioneer of membrane technology in India. Permionics has the unique distinction of being the first and only company in India till date to indigenously manufacture Reverse Osmosis (RO), Ultrafiltration (UF) and Nanofiltration (NF) membranes for various process specific applications and wastewater recycling, zero liquid discharge, purified water, desalination of sea water and USP purified water system.
Conclusion :
Wastewater Treatment plays an important role in keeping our environment clean, healthy, and sustainable. We treat wastewater, cut down on pollution, save water, and boost community health. At Permionics, we take pride in being a reliable partner in managing wastewater. We provide groundbreaking solutions that help save water, lessen environmental damage, and create a brighter future for everyone.
