What are collection systems?

The collection systems form a part of sanitary engineering, which is a sub-branch of civil engineering. It is also known as public health engineering and wastewater engineering. It is a methodology followed to remove and properly dispose of human waste, along with creating systems to provide safe and clean usable water. These measures ensure a hygienic and disease-free community. Sanitary engineering, apart from building sewer disposal units, is also involved in plumbing, fire protection, hydraulics, life safety, environmental protection, information technology, microbiology, pathology, and so on.

This area majorly emphasizes the design and construction of collection systems for wastewater disposal, sewer disposal, wastewater collection and treatment, sanitary sewer management, recycling centers, public landfills, and so on. Sanitary engineering also pays attention to reverse effects of soil damage and water pollution.

Collection systems refer to the building of structures and underground pipe layouts to convey wastewater to water treatment facilities, which makes the water usable and consumable. It also engages in building sewer collection facilities and human waste collection structures to safely collect and dispose of the wastes from households and municipal areas. Apart from building sewer and waste collection systems, a collection system may also involve building systems to collect wastewater from natural resources and precipitation such as stormwater collection, rainwater collection, groundwater collection and filtration, and so on.

Wastewater collection systems

The sanitary collection systems mainly collect wastewater and human waste from residential, commercial, and industrial units. Before letting these wastes be discharged into natural water bodies and environmental dumps, they are transferred to sewage treatment plants. Most of the industrial units have their own inbuilt wastewater collection systems and sewage treatment plants.

The wastewater needs to be collected and managed in various centralized and semi-centralized collection treatment plants. The task is generally done by building sewer systems or by building cartages. Building advanced sewer systems on a large scale is expensive regarding installation, and maintenance, but there are many ways to make it cost-effective. Few measures such as simplifying the network of pipes, reducing the number of pumps, reducing the size of the treatment plants such as building Decentralized Wastewater Treatment Systems (DEWATS), these few optimizations provide a very cost-effective approach in building a collection system. Building manual cartages also serve the purpose but it brings a lot of risk factors for the collection agency (especially when the wastewater is diluted), which involves the collection of the contents. Instead, the collection agency can use a gulper and vacuum truck to suck out the wastes out of the cartage which will significantly reduce the chances of health hazards.

Wastewater treatment

The wastewater treatment majorly involves the conversion of wastewater and other harmful by-products such as black water, fecal sludge, greywater, non-biodegradable water, urine contaminated water, and so on, into safe reusable water. It also transforms these wastes into purified water which can be safely disposed into the environment that reduces potential health hazards and diseases. The main content and the equipment in these wastewater treatment plants are involved in removing or the treatment of solid wastes (total suspended solids), biological and chemical oxygen demand, nutrients (mostly nitrogen and phosphorous), and pathogenic microorganisms like broad-spectrum bacteria, viruses, harmful fungi, and so on. The plants also remove other contaminants such as heavy metals, pesticides, and different chemicals. Residential wastes involving domestic wastes are often treated biologically, whereas industrial units such as pharmaceutical and pesticide manufacturers are treated with chemical treatment processes. The collection systems consist of various utilities including force mains that remove the wastes out of the storage units under high pressures via pumps and transfer them into portable tanks which can be transferred to the treatment plants.

Process flow architecture of a typical sewer treatment plant.
CC BY-SA 2.5 | Image credits: https://commons.wikimedia.org | Leonard G

Uses of reclaimed water

Water reclamation is a term that refers to wastewater reuse or wastewater recycling. The plant-treated water can be reused for various purposes, some of its uses are outlined below.

Urban use

The reclaimed water is mainly used in place of drinking water to serve various purposes such as washing cars in car washing garages, flushing public and commercial toilets, masonry purposes, cleaning and washing purposes, water for cooling towers, building artificial lakes, public fountains, irrigation for gardens and golf courses, and, hydraulic equipment.

Agricultural use

The wastes act as fertilizers for agricultural uses. This is also called excreta reuse. The wastewater from domestic and municipal sources acts as a nutrient source for crops if it contains compounds such as nitrogen, potassium, and phosphorous. Several force mains and related utilities are connected across the agricultural fields that pump water to the crops using a network of pipes and sprinklers. This method is very useful when there is a shortage of water due to the lack of precipitation in the area and other environmental conditions.

Planned portable reuse

Planned portable reuse is an intentional project regarding the transformation of wastewater from a sanitary sewer into portable and safe drinking water. In this case, various advanced treatment and water purification processes are involved to discharge heavy metals such as iron, harmful chemicals and toxins, and microorganisms. Technologies such as reverse osmosis, ultraviolet rays, and so on act as the main contents of such treatment plants.

Besides providing safe drinking water, these technologies have certain risk factors which directly relate to the use of chemicals and artificial processing methods.

Context and Applications

This topic is majorly taught in many undergraduate and postgraduate degree courses of:

  • Bachelors in Civil Engineering
  • Bachelors in Mechanical Engineering
  • Masters in Environment and Engineering
  • Masters in Management Technology (Wastewater)

Practice Problems

1. Which of the following nutrients is essential for crops in agricultural use?

  1. Nitrogen
  2. Phosphorous
  3. Potassium
  4. All of these

Answer: Option d

Explanation: Nitrogen, phosphorous, and potassium are the three most important nutrients needed by crops from the agricultural point of view.

2. Which of the following collection systems possesses a potential health hazard for the collection agency regarding the collection of the contents?

a. Past-due

b. Debt collector

c. Both a and b

d. Cartages

Answer: Option d

Explanation: Emptying the contents of the cartages possess certain health hazards to the collection agencies. Out of which, dilution of wastewater with harmful chemicals is one of the main risk factors.

3. How wastes from the collection systems are transferred to treatment plants?

  1. By the use of force mains.
  2. By the use of pumps and force mains.
  3. By force mains and cloud-based approaches.
  4. By cloud-based approaches only.

Answer: Option b

Explanation: Both force mains involving a network of pipes and pumps are used to transfer the wastes to the sewer treatment plants.

4. Which of the following forms a collection system?

  1. Debt collection system only
  2. Sewer collection and treatment
  3. Stormwater collection and management
  4. Dams and debt collection systems

Answer: Option d

Explanation: Sewer collection and treatment along with stormwater collection and management are examples of collection systems.

5. Which of the following technology is used in the water purification process to convert wastewater into drinking water?

a. Ultraviolet rays

b. Reverse osmosis

c. Iron filtration

d. All of these

Answer: Option d

Explanation: Technologies such as ultraviolet rays, reverse osmosis, and iron filtration is used in the conversion of wastewater into portable drinking water.

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