The Indian government tightens the limits for wastewater release in rivers and lakes. As a result, industries and municipalities struggle to comply with government rules. In addition, there is no universal treatment solution that fits every company. For example, pharmaceutical and food industries require tertiary treatment, while other industries might not. However, a customized treatment system can be beneficial, but tailoring it according to pollutant types, budget, and water source can be challenging.
Let us read further what shall be considered before designing a wastewater treatment plant.
What are the essential points to consider when designing a water or wastewater treatment plant?
- Effluent concentrations
When wastewater comes from different sources, it consists of different concentrations of contaminants. Thus, the plant design must be done keeping in mind the wastewater source. For example, industrial wastewater requires more filtration systems as compared to domestic wastewater as it is more concentrated. Hence, the effluent concentration consideration ensures the right plant design.
- Area selection
Most of the time, wastewater treatment plants require a colossal area for installment, which might not be convenient in this high-population country. Here, common treatment plants or compact designs can be beneficial.
Moreover, the topography of the site also plays a significant role. If the area is a little sloppy, it assists the wastewater flow in the plant and minimizes the requirements of pumps and motors.
- Layout design
A good layout design can include the following criteria,
- Location of plant downwind of residential areas.
- A considerable distance between plants and residencies.
- Foul-smelling units away from the residential area.
- A cover for odorous units or ventilation systems.
- Odor controlling supervisions
A wastewater treatment plant always produces pungent odors and sometimes toxic gases too. It creates problems for people working in the plant and also for the nearby residencies.
However, water treatment plant manufacturers nowadays comprehend the chemistry of odors such as sulfides, mercaptans, methane, etc., and can mitigate it. Moreover, they also incorporate technologies in their designs that cover and treat foul odors.
- Chemical and biological scrubbers
- Many conventional water treatment plant manufacturers use chemical scrubbers in plant designs that involve the use of sodium hydroxide and other oxidants to oxidize odorous compounds and produce non-toxic byproducts.
- Modern plant technologies incorporate biological scrubbers to eliminate the use of chemicals and reduce environmental footprints. Well-designed biological scrubbers can minimize nearly every odorous compound.
- Foul-smells can be confined by housing the odor-causing processes, providing proper ventilation, and directing them to scrubbers.
- Another approach is by providing piping systems that spray fragrant chemicals and are often attached to the plant’s periphery.
- Protection of neighborhood
As wastewater treatment plants come with pros and cons, the nearby residents might frown upon their installation. Moreover, the neighborhood should be protected from smells, poor sights, and noise levels by employing fencing, ventilation, and scrubbers in the plant design.
- Address noise pollution
Many equipment in the treatment system produces high levels of noise which can contribute to noise pollution and might be harmful to workers in the long run. This can be prevented by using equipment with low decibel ratings.
- Future expansions
When designing a wastewater treatment plant, future expansion plans must be considered. Therefore, provisions for the expansion of units and systems like pipelines and blowers shall be provided.
Some technical factors to consider before designing a WWTP
- Characteristics of wastewater
Characteristics of wastewater are highly considered during the design of a treatment plant because of the,
- Uncertainties related to the type of industries and manufacturing processes.
- Differences in calculated parameters and actual wastewater parameters.
- The total amount of biological oxygen demand (BOD) to degrade organic impurities.
- The total amount of chemical oxygen demand (COD) to oxidize chemicals.
- The total amount of carbon present in the wastewater
- Opinions from other experts
The operation team often might demand a filter or screen system in the inlet of a major unit to avoid unexpected debris. However, it is neglected to save money, and as a result, chances of deviations increase, doubling up the costs. Similarly, construction and commissioning teams better understand challenges than a design team.
Thus, it is essential to consider the inputs from the operation, commissioning, maintenance, and construction teams.
- Requirement of treatment stages
Generally, wastewater is treated in three stages: primary, secondary, and tertiary stages. However, depending on the types of pollutants, sometimes pre-treatment is necessary. In addition, pharmaceutical, food and beverage industries, and sewage treatment require solid secondary treatment that includes bioreactors. At the same time, many sectors might not need tertiary treatment: filtration and ultrafiltration.
The design of the process depends on the quality of wastewater.
- Maintenance and operational flexibilities
Sometimes, plants are pulled down because they fail to meet water quality standards. Here, management should ensure proper selection of stages, processes, and equipment units.
Additionally, plants should allow equipment maintenance with the concept of sparing. As a result, the plant can achieve high efficiency with standby units, encouraging the ‘n+1’ formula.
In the initial stage, plants may not receive full flow, and management should be prepared for lower flow rates for months. Water treatment plants should be able to operate between 20-35% flow rate.
- Sophisticated technologies
The design team should consider the contaminants present in the wastewater, which include material in soluble or particulate form, cleaning agents, solvents, by-products, and other matter. Some of the complex compounds in the wastewater require sophisticated equipment and processes.
Neutralization is the process of adjusting the pH of wastewater by using acid or base. It is a critical step in the primary treatment to ensure proper pH range. pH maintenance is also essential to ascertain further operations. The design and construction material of the neutralization tank should resist corrosion.
Many wastewater treatment plants have been demolished because there was no scope of correction in the design and construction of the plant. Hence, a professional and trustworthy treatment plant manufacturer follows the government guidelines for the design, construction, and operation of wastewater treatment plants.