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Wastewater Treatment Practices in Pakistan (Part 2)

"Wastewater Production and its Primary Treatment Methods"

By Fatima JamilPublished 3 years ago 3 min read

1.1-Watewater Treatment Practices in Pakistan along with its Production and Primary Treatment Methods:

1.2-Wastewater Production

According to the 1998 population census of Pakistan, we estimated the total wastewater discharge from the 14 metropolitan cities of the Pakistan, which is about 1.83 × 107 m 3 h −1. But the latest data revealed that the water quality has been continuously decreased day by day and its production reached up to dangerous level. The total wastewater discharge is about 277,765 million gallons from industrial waste and 672,979 from domestic waste. Industries like, Paper, Textile, Petrochemicals, Refineries and food are the major source of the industrial wastewater generation. It was also estimated that 1990 million gallons of wastewater are directly discharged to the natural bodies without any primary treatment. Here is sector wise wastewater generation in the Pakistan.

1.4-Process Overview

Sewage should be treated close to area where it is produced, or we transported the waste through a network of pipes to the treatment plants. The collection and treatment of the sewage is directly relates to the National and local authorizes with regulations. This treatment process involves the three main stages.

Primary Treatment

• Secondary Treatment

• Tertiary Treatment

1.5-Pre-Treatment

This method is used for the removal of material that easily be separated from the waste water before it blocks the pipelines or damage the clogs of pumps. By following this treatment we easily remove large heavy bodies from water and it is considered the most important step towards the treatment of wastewater. This method includes following processes;

1.5.1-Screeing

Wastewater is strained to remove all the blocking material like sticks, metal cans, plastic bags, and tampons that are present in the sewage. In large automated plants this process performed mechanically, but small unit areas done this process manually. For mechanical automated system we used raked bar screens. These plants are workable for a large mass of waste and their action directly relate to the flow rate of the effluent. They screen the sewage water and remove the large objects present in it. The removed particles are collected and dumped far away from places.

1.5.2-Grit Removal

In this pre-treatment method we used cambers filled with sand and grit channels to control the velocity of incoming water. The wastewater moves slowly to allow macro particles to settle down, while the organic suspended particles move towards the next chamber. It also contains a sand washer along with conveyor that is used for the transport of sand to the discharge cell. The removed sand is further moved to sludge processing plants or to a landfill.

1.6-Primary Treatment

Although there are three basic treatments to treat wastewater called primary treatment, secondary treatment and tertiary treatment. But in this article our main focus will be on primary treatment. We will discuss the important step that is involved in primary treatment. In primary treatment the wastewater is collected in a tank basin, called “Primary Sedimentation tanks” where the heavy metal particles are settling down, and lighter particles moves up to the surface. The sewage starts to flow from a giant tank, also known as “Primary Clarifiers”. These tanks are large and easily settle down the sludge. In this way the settled and floating material easily separated from the rest, which further pass towards the secondary treatment process. The main purpose of Primary Sedimentation tanks is to create a suitable homogeneous waste liquid that are easy to handle or treat through various Physical and Biological means. The sedimentation tanks are linked with automatic driven scrapper. Scrapper used to collect the sludge material from the waste and ultimately pass towards a hopper for further treatment.

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Fatima Jamil

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