Taking a look at municipal and industrial wastewater treatment 

The Amendments to the Federal Water Pollution Control Act in 1972 set the objective to restore and maintain the chemical, physical, and biological integrity of U.S. waters. The Clean Water Act (CWA) ensured that the communities have access to clean water by regulating the number of contaminants in the nation’s waterways and its treatment through primary and secondary channels.

Wastewater has the natural ability to treat itself with time. But with increasing population and industrial activity, increased levels of treatment before discharging municipal and industrial wastewater is needed.

The United Nations Sustainable Development Goals (UN SDGs) has set targets for improved water quality, integrated water resource management, improved water use efficiency, and restored water-related ecosystems.

During the first half of the 20th century, municipal and industrial wastewater was combined and sent for treatment via a single drain. This process lead to health hazards for human and marine life and required segregation of municipal and industrial wastewater.

Pollutants in Municipal and Industrial Wastewater

Industries such as chemical, electric power, food processing, iron and steel, mining, nuclear, automotive, and paper and pulp are some of the major contributors to wastewater pollutants. For example, on average 70 million cars are produced globally every year, contributing over 34 trillion liters of wastewater. These pollutants, if released into streams and groundwater untreated, can be a hazard for human and marine life.

If treated efficiently, municipal and industrial wastewater can be a valuable source of energy and nutrients. For example, sludge from municipal wastewater can be used to extract energy and bio-solids for agricultural use, whereas phosphorous from eutrophication can be used in manufacturing fertilizers. 

Treating wastewater is not as simple a process as it used to be half a century ago. Increasing population, CWA guidelines, changing EPA regulations with a focus on health and safety, throw newer challenges to segregate and process the wastewater.

There cannot be a single universal solution to industrial and municipal wastewater management. Tailoring wastewater treatment according to the water source, pollutant types, geographical location, budget, and availability of technology is the primary challenge. Other challenges include –

Additionally, many wastewater collection and treatment facilities that are old and worn require improvement and maintenance to extend their life. This requires continuous monetary and technology investment.

Off-site treatment facilities usually collect wastewater from municipal and industrial drainage systems and process it via various methods to separate different types of waste. Wastewater is also stored inside the industrial units in closed-top frac tanks before transporting it to the processing facility. Wastewater treatment can be broadly divided into three categories –

At this stage, wastewater is passed through filtering devices that remove coarse solids which comprise up to 50% of suspended pollutants. The filtered material is called primary sludge which is then sent for bio-solid treatment.

At this stage, biological organisms are used to naturally separate pollutants from wastewater. The solid waste thus produced settles at the bottom of the tank and can be easily removed. The waste produced is called secondary waste or biological sludge. The bio-solids thus produced are either used as natural fertilizers in farming and landfill for energy production. Bio-solids can also be incinerated to break into simpler substances that are released into soil, air or water.

At this stage, chemical treatment methods are used to remove the pollutants from wastewater before releasing it into natural water bodies.

Some of the specialized technologies used to treat wastewater that fall under either of the three broad categories mentioned above are –

As cities and industries continue to grow, monetary and intellectual investments are needed in efficient and sustainable ways of treating water discharged from municipal and industrial sources. Wastewater should be considered a valuable resource from which energy can be extracted, before releasing the nutrient-rich water back into the streams for marine life.

The key is to adopt a circular wastewater management model that adds to the economy, recovers resources, and reuses them via a self-sustainable process.

The Water & Wastes Digest staff invites industry professionals to nominate the water and wastewater projects they deem most remarkable and innovative for recognition in the Annual Reference Guide issue. All projects must have been in the design or construction phase over the last 18 months.

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