Residential and Commercial Wastewater Treatment Plants
Residential wastewater or domestic sewage are the terms used to describe the wastewater generated within a household by food preparation, appliances, personal hygiene, etc. Residential wastewater is broken down into two types:
Blackwater: wastewater from toilets
Greywater: wastewater from all other sources
Although both types have different properties, each contains a variety of pollutants and must be treated.
Commercial wastewater is generated from businesses (excluding manufacturing and construction), such as shops and shopping malls, markets, office buildings, restaurants, hospitals, hotels, etc.
Wastewater from commercial sources contains contaminants and treatment is required.
In this blog post, we will focus on commercial and industrial wastewater and the types of treatment plants.
What is Filtration for Water Treatment?
In general, after use, wastewater requires treatment before it can be returned to the environment and there are strict regulations in place to make sure that facilities are compliant.
There are several types of treatment plants for wastewater, depending on the water source and level of treatment necessary.
Wastewater Treatment Plant (WWTP)
Treats water from residential, commercial and industrial use. By treating wastewater, the resulting clean water can then be reused for industrial uses, such as cooling tower makeup water, and for agricultural and landscape irrigation purposes and even for drinking water.
Filtration can be found in various stages of the treatment process, most commonly at the tertiary treatment stage. Here is a brief explanation of each stage:
- Collection Sewers: collecting all of the industrial wastewater from the various production processes
- Pumping System: distributing the wastewater to the subsequent treatment processes
- Bar Screening: removal of coarse debris, sand, rocks, etc.
- Chemical and pH Adjustment: adding chemicals to bring the pH levels to an optimal level
- Primary Treatment Tank 1: open settling tank
- Primary Treatment Tank 2: open aeration tank
- Secondary Treatment: clarifier
- Disinfection: chlorination or UV treatment
- Tertiary Treatment: final polishing stage, filtration to reduce the TSS and BOD levels
- Sludge Dewatering / Decomposition: drying the sludge for disposal or reuse as fertilizer according to strict environmental regulations
Below is an illustration of a typical wastewater treatment plant describing the various treatment stages:
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You can find detailed information on these wastewater treatment processes in our related blog post.
Sewage Treatment Plant (STP)
STP’s treat residential and commercial sewage waste and occasionally commercial wastewater as well.
Sewage normally has high levels of organic matter but may also contain inorganic waste.
The treatment process includes primary, secondary and tertiary stages.
Effluent Treatment Plant (ETP)
ETP’s treat industrial effluents containing heavy metals, oil & grease, phosphorus other contaminants. The treatment process usually involves physical, chemical and biological treatments.
It is vital that wastewater be treated before reuse or prior to being returned to the environment to prevent contamination.
Reverse Osmosis Water Treatment
Reverse osmosis treatment is a water purification process used to significantly reduce total dissolved solids, organic pollutants, heavy metals, bacteria and other dissolved contaminants using pressure to force the water through semi-permeable membranes. After treatment, wastewater can be either reused or disposed of safely.
RO membranes are relatively expensive and in order to protect them, fine filtration is utilized to prevent clogging and physical damage to the membrane surface and layers and to reduce the formation of biofilm.
Used as a final polishing stage after tertiary treatment, usually for industrial reuse.
Demineralization Treatment Plants
Demineralization, sometimes called deionization, is a physical process to remove mineral salts by using ion exchange.
Water treatment with demineralization is reused in a variety of industries, such as chemical/pharmaceutical, power plants, textile automobile and oil and gas.
This process uses 2 ion exchange resins – anion: releases hydroxyl ions, typically negatively charged and cation: releases hydrogen ions, typically positively charged.
There are two methods of demineralization:
1. Two-bed: this method uses 2 vessels, one with a cation resin and one an anion resin. Water flows through the cation exchanger first, where cations are replaced with hydrogen ions. The water then flows through the anion exchange and anions are replaced with hydroxyl ions.
2. Mixed-bed: the cation and anion resins are combined in one pressure vessel. Although this method is more efficient than the previous one, the process is more complex, and it is utilized when a higher level or purification is needed. The mixed-bed method is also used as a polishing stage after the two-bed method.
Innovative and Smart Industrial Wastewater Treatment Plant Use Cases
Wastewater treatment plants treat water from a wide variety of sources – from domestic use, commercial activities and industrial applications.
Here are a few examples of how Amiad’s filtration solutions for wastewater were implemented:
Containerized Tertiary Wastewater Treatment, Ireland
The existing system was struggling to cope with the loading placed on the WWTP and in particular the final effluent TSS (Total Suspended Solids) was very close to the site’s discharge limit of 30 mg/l TSS. The group was looking for a cost-effective upgrade to the WWTP which would ensure continued compliance with the site’s discharge consent. The existing site had limited space for any new system and needed a solution which was cost effective and could fit into the area available, while maintaining production throughout the project.
Recycling Dairy Farm Wastewater for Irrigation, USA
The dairy uses fresh water on a daily basis for its normal operations such as washing the cows, the milk-producing process and for the supply of drinking water for the cows. These tasks produce wastewater, mostly from washing the cows and the milking process and this water is collected in ponds. In order to use the pond water for irrigation, a filtration solution was required with the ability to handle high loads of suspended solids as well as the suspended organic loads from the pond.
Skid Mounted Tertiary Water Treatment Plant, Australia
Logan Water Alliance in Australia needed a packaged tertiary water treatment plant that would be able to reduce total suspended solids and turbidity.
The solution installed was a 2-stage system including screen and multi-media filtration.
Wastewater Filtration in an Aquifer Thermal Energy Storage (ATES) System
This project utilizes municipal wastewater as a heating source for the groundwater. The energy from the wastewater is transferred via heat exchangers to the ATES building and reliable filtration was required to protect these exchangers.
The solution runs on very low pressure, adhering to the concept of using the smallest amount of energy possible.
Cost Saving Solutions
Operating wastewater treatment plants is costly, and the aeration process normally utilizes the most energy of all the processes. This would be the best process to analyze and optimize for savings.
Blowers have a lifetime of approximately 20 years, even when maintained as required. This technology has seen much improvement over the last few years and high-efficiency turbo blowers have the ability to be adapted for the dissolved oxygen quantity needed. They also have a broader operation range than units installed decades ago.
An alternative solution is using a variable frequency drive (VFD) to make older centrifugal units more efficient.
Here too there have been improvements recently. Fine bubble aeration diffusers increase oxygen transfer efficiency resulting in a decreased aeration demand which leads to a reduction in electric power consumption.
Recovery of energy
The anaerobic digesters at wastewater treatment plants produce methane biogas which can be used to generate electricity and heat. Methane biogas is also created by the digesters in the sludge stabilization process which can be burned in engines for electric power or operations.
Instead of being connected to electric motors, piston engines can be linked to aeration blowers, with the biogas supplying the required energy, thus saving electric power.
By using heat recovery steam generators (HRSG), high-temperature biogas combustion exhaust boils water and the resulting steam is then used to operate blowers. This method can be used instead of electric motors, saving energy and costs.
Reduce chemical use
Chemicals are costly and can be hazardous. By using UV disinfection systems, instead of chemicals, costs can be reduced.
Additionally, chlorination is the method most widely used to treat wastewater as it is very effective at removing bacteria and viruses.
However, using chlorine results in the formation of trihalomethanes (THMs), a result of a reaction between chlorine and the natural organic matter in water.
TMHs are environmental hazards and some have been labeled as carcinogenic. Treatment by dechlorination (the process of removing residual chlorine from disinfected wastewater prior to discharge into the environment) is essential to protecting aquatic life and making sure that the wastewater is safe for reuse.
An easy fix is replacing older energy-consuming fluorescent light fixtures (T-12) with newer, more efficient fixtures (T-8).
Take advantage of gravity
Gravity is cost-free and plays an important role in how flow is transported in wastewater treatment plants. When making process improvements, check if gravity is being maximized.
Automate operations (IoT)
Supervisory Control and Data Acquisition (SCADA) systems automate wastewater treatment plant operations and enable operators to monitor equipment remotely, allowing them more time to perform other tasks. Data on equipment and processes can be analyzed to determine when the use of energy can be reduced.
Also, smart control (IoT) is becoming more and more popular in order to optimize performances of wastewater treatment facilities.
Amiad’s Unique Wastewater Treatment Filtration Technologies
With a full range of water filtration technologies, Amiad offers solutions for efficient wastewater treatment.
Suction-Scanning Screen Technology
Combines a focused flush with suction scanner automation to provide self-cleaning of a multi-layered stainless-steel screen to ensure high-efficiency filtration.
Spin KlinTM Disc Technology
Grooved plastic discs provide a large filtration volume for retention of organic matter by providing depth filtration with high dirt holding capacity.
Available with a wide range of media types – sand, glass, active carbon, anthracite, basalt, etc. and various tank construction materials, meeting international drinking water standards.
Fine microfibers wound in layers around grooved plastic form the thread cassettes, providing filtration to a fine degree with an efficient self-cleaning system.
This technology received approval for use under the California Water Recycling Criteria, also known as Title 22.
Selecting the Right Wastewater Filtration System
Selecting the right wastewater filtration system can be challenging. Below are some of the factors to take into account that can help understand the basics, but consulting with professionals is crucial.
Water Source and Quality – Another major factor in choosing the right solution is knowing the water source. Does the water contain chlorides or oil and grease? What is the pH of the water? Are we dealing with water heated to high temperatures? All of these will determine what construction material will be used for your filtration system, and how simple or complex it will need to be.
Type/Load of Contaminants – This has a direct effect on the choice of filter. Do we need to remove organic materials, minerals, maybe paper fibers? Different types of contaminants require different filtration solutions.
Particle Size Distribution (PSD) – Understanding the PSD in your water will also affect the type of solution you will need. In some cases, a coarser solution will give sufficient results with no need for much finer filtration.
Each technology has advantages and disadvantages, depending on the application, water source and which contaminants are contained in the wastewater.
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Sizing based on application and micron range:
Our filtration experts will be happy to assist you with selecting the best filtration system for your wastewater filtration needs.
Click here to contact one of our experts