Municipal vs Industrial Wastewater Treatment Technologies

Wastewater treatment is a major challenge when it comes to population growth and expanding production in various economic sectors.?

Wastewater is a byproduct of virtually every human activity and can contain a variety of pollutants, each of which differs in their effects on the environment and the processes required to treat them.?

Globally, only about 20% of all wastewater gets treated, with the rest being discharged with minimal to no treatment. And, just to treat this portion of wastewater, we are releasing greenhouse gas (GHG) emissions greater than the entire shipping industry. As industries and cities increasingly strive to achieve their net-zero goals, they need to consider the impact of wastewater on these.?

Consequences of untreated wastewater include ecological damage, polluting drinking water, and increased greenhouse gas emissions, with the effects varying depending on the source of wastewater.?

The three major categories of wastewater are as follows:?

1.????? Municipal wastewater?

2.????? Industrial wastewater?

3.????? Agricultural wastewater?

Each category of wastewater poses its own distinct challenges with regards to treatment needs and the technologies used to address them, particularly regarding secondary wastewater treatment, which deals with organic pollutants in the wastewater.?

In this article, we explore municipal and industrial wastewater treatment, including some of the complexities of treating each and common technologies used for each form of wastewater.?

Municipal Wastewater and Relevant Technologies?

Municipal wastewater, commonly referred to as sewage, is the effluent that comes from domestic households and businesses.?

Municipal wastewater tends to be more diluted compared to industrial wastewater, and typically contains fewer toxic compounds, although this is not always the case.?

Municipal wastewater treatment challenges?

Municipal wastewater has a few specific challenges when it comes to consistent and effective treatment.?

The following are a few examples:?

1.????? Stormwater fluctuations?

Because municipal wastewater usually includes storm drain effluent, fluctuations in weather lead to increases or decreases in the total volume of water produced. During periods of higher volumes, stormwater can overwhelm treatment facilities, causing direct discharge of sewage and stormwater to the environment.?

Additionally, this leads to variations in the strength of wastewater and the contaminants it contains, which can make it difficult to keep treated wastewater within acceptable contaminant levels during storm season.?

2.????? Aging infrastructure?

Like many areas of human development, populations tend to grow faster than the infrastructure that supports them, and this includes municipal wastewater treatment plants. Larger populations proportionally increase the demand on municipal treatment facilities, which means they must scale up or upgrade to ensure they can meet rising demands.??

Across all wastewater treatment plants in the US, they are operating at 81% of design capacity, and 15% are at or have exceeded capacity. Investment in infrastructure has lagged what is required, and according to the American Society of Civil Engineers, there is a $105 billion funding gap for drinking water and wastewater infrastructure projected over the next two decades.?

3.????? Freshwater usage reduction efforts?

With the overall push to reduce freshwater usage in areas of high water-stress, wastewater streams have become more concentrated in these localities. Higher concentrations require more intensive treatment, increasing the need for capital expenditure to upgrade municipal plants.?

Overall, the challenge boils down to an increased need for investment in municipal wastewater treatment plants, including size upgrades and installing improved technology.?

Municipal wastewater treatment technology?

Most municipal wastewater treatment depends on aerobic processes to deal with organic compounds within the wastewater stream. The following are a few common technologies used in municipal wastewater treatment.?

Activated Sludge?

Activated sludge is a biomass layer contained in a treatment tank and consists of microorganisms that digest organic materials in the water and rely on aeration to maintain the correct microorganism blend.?

Activated sludge is effective at treating low to medium strength organic wastewater such as municipal effluent but has a high energy demand due to the aeration requirements.?

Trickling Filters?

Trickling filters involve bacteria attached to a medium through which wastewater is filtered through. It is a simple biological process that can rapidly reduce biological oxygen demand (BOD) pollutants and can handle reasonably high concentrations.?

However, it requires maintenance to ensure the bacterial colonies remain aerobic and that excess slime is removed as it builds up.?

Membrane Bioreactors (MBR)?

Membrane bioreactors combine activated sludge with a membrane filtration unit. They are very efficient and have advantages over conventional activated sludge methods. They generally have a smaller footprint and produce high quality effluent free from bacteria and pathogens, reducing tertiary disinfection needs.?

Often, MBR treated effluent can be discharged directly and to receiving bodies of water or reclaimed for irrigation and other non-human consumption uses.?

Industrial Wastewater Challenges and Technologies?

Industrial, or point source, wastewater consists of the effluent from various manufacturing and production facilities. It is typically much stronger than municipal wastewater and contains higher levels of toxic contaminants and organic compounds. Industrial facilities will have a discharge permit, which provides the levels of pollutants they are allowed to discharge. Compliance and enforcement of these depends on the company’s priority and the city’s resources to monitor.?

Industrial wastewater treatment challenges?

Onsite treatment of process wastewater typically falls outside the expertise of the company and distracts from their core business operations. The specialized knowledge, cost and technology to effectively treat wastewater usually means that companies will not invest in onsite treatment until they are forced to by their local authorities.?

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