Introduction

Although, both these terms are used interchangeably, they are actually two different systems with different purposes, structures, treatment methods etc. These discrepancies result in wide variation in technical performance and environmental impacts. In the following blog, we’ll discuss these two types of treatment plans, examine their differences and why they are important to know when it comes to making the best wastewater management decisions. This understanding is essential to any policymaker, environmental professional, or citizen with an interest in water treatment who needs to make sense of a field of increasing complexity.

Describing the Source: The Essential Distinction

The key distinction between WWTP and STP is in the input loads and nature of the effluents. Although both are in the business of treating water to benefit public health and the environment, their processes are quite different because of the origins of what they treat.

Sewage Treatment Plant (STP):

Source:STP is solely designed to deal with domestic sewage or municipal wastewater.

Contents: Sewage is composed largely of naturally-occurring substances and organisms which, over time, can be reduced to beneficial properties in the wastes that it cleans. The refuse is usually biodegradable and relatively consistent in composition, ie., its constituent has a high degree of predictability and the characteristics of the waste water are maintained at a pretty constant level. Major pollutants present in sewage include BOD, COD, nutrients (nitrogen and phosphorus), and pathogens. And while it can be laced with some chemicals, the levels tend to be low and can be addressed through biological processes.

Wastewater Treatment Plant (WWTP):

Source: WWTP are facilities that process wastewater from any source: Trade, agriculture and even sewer (from cities and so on.) Above all, let us make clear that by that, when referring to industrial WWTP, we are precisely referring to treatment plants of wastewater generated by industrial activities.

Composition Industrial waste water is extremely varied in composition, some types containing toxic chemicals, heavy metals, organic compounds, and solvents. They can be such things as pharmaceutical byproducts, petrochemicals, salts, solvents—all these things are not biodegradable and they can be toxic to biologic treatments. Toxic compounds are present in industrial water that necessitates special treatment process technologies.

Contrasting Treatment Objectives and Processes

Influent (incoming wastewater) compositions for STPs and WWTPs differ, leading to separate treatment goals and methods. What are the treatment options for each?

Sewage Treatment Plant (STP) Process:

A STP is mainly designed to remove organic matters, pathogens, and nutrients in such a way that would prevent water bodies from getting polluted and avoid public health issues. It is essentially a biological process, natural microorganisms are able to degrade organic matter.

Primary Treatment: This is a physical procedure and includes removal of coarse solids by screening and sedimentation to remove heavier solids. Pretreatment removes approximately 60% of solids as the primary treatment.

Secondary Treatment: The heart of the treatment process, with biological treatment being employed. To break down dissolved organic material, microorganisms are introduced. An activated sludge process is a typical process for this stage, where oxygen is provided to promote the growth of aerobic bacteria which feed on the organic contaminants.

Tertiary treatment: This ultimate process allows the treated water to be refined. It can be nutrient removal (nitrogen and phosphorus), filtration, and disinfection. Conventional disinfection approaches, such as UV radiation or chlorine, further kill any remaining pathogens so that the treated water can be safely discharged into rivers or lakes.

Wastewater Treatment Plant (WWTP) - Industrial Process:

Treatment of industrial waste water are complicated due to the existence of toxic, non-degradable compounds. The chemical and physical processes are most common, although some biological processes, especially in select cases, also have been considered. The intended aim is not only to eliminate organic material but to also to neutralize or remove substances that are detrimental to the environment or harmful to human health.

Pre-Treatment, the key first stage of treatment, in which the pH levels are adjusted, heavy metals are precipitated, and complex chemicals are oxidized. This gives the wastewater the proper condition to receive biochemical or chemical treatments afterwards, and avoids the harming of the other biological systems further integrated.

Pretreatment/Chemical Treatment: Traditional precipitation, electrocoagulation, and AOPs have been used to treat this stage. These approaches are directed at certain pollutants such as heavy metals, solvents and other harmful chemical compounds that are not biodegradable by biological processes only. AOPs for example apply strong oxidizing agents such as ozone to degrade resistant compounds.

Biological process If biodegradable organics still remain after pre-treatment, biological treatment is applied. Nevertheless, the wastewater is polluted by toxic compounds, and the treatment could have to be assisted with some kind of specialized cultures dealing with one kind of pollutant.

Polishing and ZLD: Following the biological treatment process, additional membrane filtration such as RO (Reverse Osmosis) and UF (Ultra-filtration) is commonly adopted to capture any residual fine particles. Further, the ZLD systems can be used to recover water from the waste streams very effectively by converting concentrated waste to solid waste for safe disposal of, by making the ZLD an imperative technology for water stressed industries.

Why the Distinction Matters

Knowing the distinction involving an STP and an industrial WWTP is important for various factors. Domestic and industrial wastewater treatment may be completely different operations and even have different pollutants and contaminates. Failing to appreciate these distinctions can have dire consequences.

For example, releasing an un-treated industrial waste stream into a city STP can self-poison the biological treatment process, shut the plant down, and be environmentally detrimental. This is because most industrial pollutants, particularly heavy metals and poisonous chemicals can retard the activity of the microorganism in an STP (which also depends on the breakdown of organic matter by bacteria). Is so doing, industries have to pre-treat their wastewater to meet the municipality’s standards before they can discharge their effluents to the public sewers. Second option is that industries have to constrcuct their own full fledged industrial WWTP to treat characteristic of their wastewater.

Key Considerations:

Regulatory Issues: If the difference is misunderstood, it can lead to failing to meet environmental regulations which can cost money (fines, penalties) and even shut down operations.

Operation Failure: Misunderstanding STPs as industrial WWTP; operational failure that municipal STPs cannot do treatment for the complex and toxic industrial waste.

Eco-Impact: The untreated industrial wastewater discharges into the municipal sewerage systems without appropriate pre-treatment can cause significant damage to the local ecosystems and water bodies.

Conclusion

So there we have it - every STP is an WWTP, but not every WWTP is an STP. An STP is that type of a WWTP that manages the expected easy biodegradable nature of domestic wastes unlike an industrial WWTP, which is tailored for the management of the complex, toxic, and non-biodegradable effluents produced by industry. Understanding this difference is crucial to properly treating wastewater so that it can be reused or discharged to the environment without causing harm to human health and the environment.

The two systems are both crucial in wastewater treatment, but the technology they employ, the processes each deals with and regulations that are applied to them tend to differ a lot. Whether you run a municipality or an industrial site, you need to know the differences to make the right treatment choice.

Amalgam Specializes in Municipal and Industrial Wastewater Plants. Our in-house team develops custom solutions for industries and municipalites, so you can be certain that your waste water treatment systems are cost efficient and compliant with the current environmental regulations.

Visit Amalgam Biotech to discover more about how we can help or provide wastewater treatment solutions