The wastewater treatment process simplified is taking organic waste put down domestic drains such as in your home and biologicolly removing the nutrients this process is regulated by the NPDES permit the clean water put through filters and disinfected / sterilized is regulated by title 22
Preliminary:
Preliminary treatment is the very first stage in the wastewater treatment process. Its main purpose is to remove large, coarse, and inorganic materials that could damage or clog pumps, pipes, and other equipment in the subsequent treatment stages. It is a strictly physical process, and it is crucial for protecting the entire plant.
The Main Steps in Preliminary Treatment
Screening : As wastewater first enters the treatment plant, it passes through bar screens. These are a series of parallel bars or a perforated mesh that act as a coarse filter. They catch large debris like rags, plastics, paper, sticks, and other solid waste. In modern plants, these screens are often cleaned automatically by a mechanical rake. The collected debris is compacted and sent to a landfill for disposal.
Grit Removal : After screening, the wastewater flows into a grit chamber. The speed of the water flow is significantly reduced, which allows heavy but fine inorganic materials, such as sand, gravel, glass, and eggshells (collectively called grit), to settle to the bottom. Unlike organic materials that tend to stay suspended, grit is abrasive and can cause significant wear and tear on pumps and pipes. It's removed from the chamber and also sent to a landfill.
Pumping : Often, as part of preliminary treatment, the wastewater is pumped to a higher elevation. This allows the water to flow by gravity through the rest of the treatment plant, reducing the need for additional pumps and making the process more energy-efficient.
Primary:
Primary wastewater treatment is the initial stage of the wastewater treatment process. It's a predominantly physical process designed to remove the large, easy-to-remove solids and floating materials from the wastewater. This stage significantly reduces the total suspended solids (TSS) and biological oxygen demand (BOD) of the water, preparing it for the more intensive secondary treatment.
Key Steps in Primary Treatment
Primary treatment typically consists of three main steps that rely on physical forces like gravity and separation.
Screening and Pumping: The very first step involves passing the incoming wastewater through large bar screens. These screens act as coarse filters, trapping large debris like rags, plastics, wood, and other trash that could clog or damage equipment further down the line. After this preliminary screening, pumps lift the water to a higher elevation, allowing it to flow by gravity through the rest of the plant.
Grit Removal: The screened wastewater then flows into a grit chamber. Here, the flow velocity is intentionally reduced, allowing heavy but fine inorganic materials—like sand, gravel, and eggshells—to settle out. Removing grit is crucial as it can cause excessive wear and tear on pumps and other machinery.
Primary Clarification (Sedimentation): The water then enters a large, deep tank called a primary clarifier or sedimentation tank. In this stage, the flow slows down considerably, allowing organic solids and other suspended particles to settle to the bottom by gravity. Lighter materials like grease, oil, and scum, which don't settle, float to the surface. Mechanical scrapers or rakes at the bottom of the tank slowly move the settled solids, known as primary sludge, into a hopper for removal and further processing. At the same time, surface skimmers collect the floating materials.
This process typically removes about 60-70% of suspended solids and 30-40% of the BOD from the wastewater, making the subsequent biological treatment much more efficient
Secondary:
The secondary biological treatment of wastewater is a crucial step that uses microorganisms to remove dissolved and suspended organic matter remaining after primary treatment. This process, which can be aerobic (with oxygen) or anaerobic (without oxygen), significantly reduces the biological oxygen demand (BOD) of the water, preparing it for further treatment or discharge.
The Activated Sludge Process
The most common method for secondary treatment is the activated sludge process, a suspended-growth system. This method is a continuous, managed process that relies on a complex community of microorganisms to break down pollutants.
Aeration Tank: Wastewater, or "effluent," from primary treatment flows into a large aeration tank. Here, air is continuously pumped into the water through diffusers or surface aerators. This provides a constant supply of oxygen, creating an aerobic environment. This environment promotes the rapid growth and reproduction of aerobic bacteria, protozoa, and other microbes.
Microbial Action: The microorganisms, collectively known as activated sludge, consume the organic pollutants in the wastewater as their food source. As they feed, they clump together to form biological flocs. This process effectively converts the dissolved and suspended organic matter into a removable biomass.
Secondary Clarifier: After a period of aeration, the mixture of treated water and biological floc flows into a secondary clarifier. This large, circular or rectangular tank allows the heavy microbial flocs to settle to the bottom by gravity. The clearer, treated water, called the "effluent," is then collected from the top.
Sludge Recycling: A portion of the settled sludge, called return activated sludge, is pumped back into the aeration tank to maintain a high concentration of active microorganisms. This ensures that new wastewater entering the system is immediately "seeded" with a healthy population of microbes, making the process highly efficient. The remaining excess sludge is removed for further processing, such as anaerobic digestion.
Tertiary / Disinfection:
Tertiary wastewater treatment, also known as advanced treatment, is the final stage of the process. It's used to further polish the effluent from secondary treatment, removing any remaining contaminants and pathogens to a very high standard. This level of treatment is essential when water is to be reused for irrigation, industrial processes, or even as drinking water, or when it's being discharged into sensitive ecosystems. 💧
Key Processes in Tertiary Treatment
Tertiary treatment is not a single process but a combination of methods, often physical and chemical, tailored to meet specific water quality requirements.
Filtration: The first step often involves a physical process to remove any fine suspended solids that were not captured in the previous stages. Common methods include sand filtration, where water passes through a bed of sand and gravel, or membrane filtration using very fine filters like microfiltration, ultrafiltration, or reverse osmosis to remove even the smallest particles and some dissolved substances.
Nutrient Removal: High levels of nitrogen and phosphorus can cause algal blooms in rivers and lakes (eutrophication), harming aquatic life. Tertiary treatment often includes processes to remove these nutrients. This can be done biologically, by using specialized bacteria, or chemically, by adding chemicals like alum or ferric chloride that cause the nutrients to precipitate out of the water.
Disinfection: This is the final and one of the most critical steps, designed to kill any remaining disease-causing microorganisms (pathogens) like bacteria, viruses, and parasites. The most common methods are:
Chlorination: Chlorine is added to the water to inactivate pathogens. This is an effective and economical method, but the chlorine must be removed before the water is discharged, as it can be harmful to aquatic life.
Ultraviolet (UV) Radiation : Water is passed through a channel with UV lamps. The UV light damages the DNA of microorganisms, preventing them from reproducing and rendering them harmless. It's a very effective method that doesn't use chemicals.
Ozonation: Ozone gas (
O3
) is a powerful oxidant that is highly effective at destroying microorganisms. It's a very fast process but can be more expensive than other methods.
Tertiary treatment ensures that the treated water is of a quality safe for its intended reuse or for discharge without causing harm to the environment.
Helpful Information
How To Get Started:
The fastest way to enter the field is with a combination of volunteering and classes. the route i took is when i graduated high school i went on to voulenteer for EMWD for 2080 hours (at the time) its now 1800 on the job hours to obtain a license, i also took the water technology certificate course through MSJC.
High School Seniors:
Getting into the work field is daunting these days let alone wondering if you should continue your education and take on crippling student loan debt I know this is controversial but I don't think you need the traditional thought of college don't take the general education all you’re doing is burning time and money if you donate 1800 hours of volunteering and take the certificate course it'll cost less than $5000 dollars that’s between the cost of class and gas back and forth to the plant and get you into a career making at least $30 an hour and only goes up every year along with state backed retirement, options for a personal 401K, medical and dental insurance included. I know looking at 1800 hours sounds like a lot but most volunteer OIT (Operator in Training) get hired before that.
Adult Career Change:
A difficult challenge in itself but if you can and should in order to expedite the process volunteer most plants are flexible on days and understand and why wouldn't they its free labor try to put in one day a week, the best class education would be MSJC but for a working adult Sacramento state office of water programs would be the way to go