Wastewater Treatment Vs Sewage Treatment: Key Differences, Benefits, And Modern Solutions

Often the terms "wastewater" and "sewage" are used interchangeably, but they are not exactly the same. They can have very different sources and pollutant inventories. It is important when choosing a treatment process.

Wastewater treatment includes water contaminated from all sources, including industrial, commercial, municipal, and other sources. Sewage normally means domestic wastewater from toilets, kitchens, washing, etc. Oils, suspended solids, heavy metals, salts, or refractory compounds can be found in industrial wastewater, while organic matter, nutrients, suspended solids, and microorganisms are found in domestic sewage.

If the project is to be based on a containerized wastewater treatment, the first step should be the actual wastewater characteristics, not just capacity. Wastewater treatment system manufacturers can be compared based on their ability to address flow rate, pollutants, discharge requirements, site conditions, and reuse goals.

What's the Difference between Wastewater and Sewage?

The most obvious difference is the origin.

Wastewater is all water that has been contaminated by industrial, commercial, municipal, or other activities. It may be different at different facilities, depending upon the pollutant produced by different processes.

Sewage is more closely related to household activities. It can come from:

• Toilets and bathrooms
• Dishwashing and laundry
• Residential communities
• Resorts, schools, camps, and the like.

Domestic sewage is generally quite consistent in composition and is a key component of many sewage treatment systems. Depending on wastewater characteristics, further physical, chemical, or membrane processes may be necessary to treat industrial wastewater.

This is the reason why the use of a domestic sewage system does not automatically imply that it can be adopted for a complex industrial effluent.

Wastewater Treatment vs. Sewage Treatment: Key Differences

The bottom-line lesson: treat water quality. If the composition of the wastewater changes, even though the flow rate is the same, the systems needed for two facilities may be quite different.

How Does a Wastewater Treatment System Work?

A treatment system typically has a number of stages. Each stage controls specific pollutants and the specific sequence of the processes is dependent on water quality and effluent desired.

Physical and Chemical Treatment

Pre-treatment can eliminate or diminish materials which may pose interference with subsequent processes.

For instance, dissolved air flotation (DAF) can be used to remove suspended solids, oils, colloids and flocs. Chemical dosing can be used to aid coagulation and flocculation and to remove contaminants such as heavy metals, phosphorus and refractory organic matter.

This kind of treatment is especially beneficial for industrial wastewater effluents, which may contain more complex pollutants than are present in domestic wastewater.

Biological Treatment

Biological treatment involves the use of microorganisms to treat biodegradable organic matter. It's a crucial point for wastewater that has a high organic content.

For domestic sewage, an AO process can be combined with MBR technology. The biological stages promote the removal of organic matter and nutrients, and the membrane removes solids from the liquid. Integrated applications like in decentralized sewage treatment use this type of configuration.

Membrane Treatment

If a higher treatment performance is desired, additional separation is achieved through membrane processes.

An MBR is a biological treatment system that uses membranes to hold activated sludge and suspended material in the system, while the treated water flows out.

In order to use the treatment systems under severe industrial conditions, the treatment systems can be configured with MBR, tubular membrane process, nanofiltration (NF), and reverse osmosis (RO). The proper mix is dependent on wastewater characteristics and the desired water quality.

More treatment stages do not necessarily mean a better system. There needs to be a clear purpose for each process.

What Are the Benefits of Containerized Wastewater Treatment?

A containerized system is a modular transportable system that includes treatment equipment. This can be advantageous in cases where normal construction methods are not feasible, space is restricted or treatment equipment must be transported to a remote site.

Important functional advantages are:

• High level of compactness: Several treatment stages can be combined into a comparatively small size.
• Transportability: The treatment unit can be taken to the necessary site.
• Reduced site construction: Pre-installed equipment can minimize site construction.
• Modular capacity: Can be expanded in multiple containers for increased capacity.
• Portable applications: Containerized systems can be used for decentralized and industrial treatment facilities.

Containerized systems can incorporate equipment, piping, valves, instruments and controls into a standard 20' or 40' container for industrial use. Several containers can be used together for more treatment needs.

Containerized AO+MBR systems can be adopted for decentralized sewage treatment on sites where a full municipal sewage system is not available, such as rural areas, resorts, islands, construction camps, etc.

How to Choose the Right Wastewater Treatment System

While flow capacity is paramount, it's not the only factor. Wastewater treatment system manufacturers should be compared after establishing the minimum parameters of the project.

Check the source of the incoming water, if it is domestic sewage, industrial wastewater, or a mixture.

Flow rate: Set average and peak flow for proper system sizing.

Pollutant profile: This may include parameters such as COD, BOD₅, suspended solids, ammonia nitrogen, oils, heavy metals, salts, and other site-specific pollutants.

Treatment target: The quality required for discharge or reuse will dictate the number of treatment stages required.

Site conditions: If space, transportation access, utilities, and installation requirements are a factor, they can affect the suitability of a containerized system.

These factors are a good foundation for avoiding the temptation of selecting equipment by capacity or for general use.

Modern Wastewater Treatment Solutions

Modern treatment is increasingly based on the concept of integrated process design. Different processes can be combined based on the wastewater to address various contaminants instead of assuming one process will eliminate all contaminants.

For instance, industrial wastewater can be treated by chemical treatment prior to biological or membrane treatment. Biological treatment with MBR separation may be more important for domestic sewage treatment. Membrane treatment can be added to higher quality reclaimed water when needed (NF or RO).

This can enable treatment systems to be designed to accommodate the application instead of applying different wastewater streams to the same treatment system.

Projects that are suitable for modular installations will benefit from QILEE's container-based wastewater treatment systems, such as configurations for industrial wastewater and decentralized sewage treatment systems.

Conclusion

Many of the technologies are common to both the wastewater and the sewage treatment processes, but they are applied to different types of water. Domestic sewage, generally, is more predictable in its contents, whereas industrial wastewater can include a broader spectrum of contaminants and may need additional physical, chemical, biological, and/or membrane treatment.

The right system begins with the water source, pollutant profile, flow rate, treatment target and site conditions. For applications where space and installation flexibility are important, a modular approach may be feasible with containerized wastewater treatment.

When companies are looking at wastewater treatment system manufacturers, the question shouldn't be what technology the system has. It is whether the treatment process is suitable for the wastewater to be treated.