Category: Chemistry

Hyperion Sewage Treatment Plant

Hyperion Sewage Treatment Plant

Hyperion Sewage Treatment Plant

11/10/25

“What is the largest sewage treatment plant in the western US, and what makes it special?”

The US has thousands of sewage treatment plants. The largest one west of the Mississippi, the Hyperion Sewage Treatment Plant, has many interesting properties. Located in the Los Angeles suburb of El Segundo, the Hyperion sewage treatment plant can treat nearly a half a billion gallons per day and recycles nearly 30 percent of its treated water for non-potable uses. The City of Los Angeles is working to make the Hyperion plant recycle 100 percent of its wastewater for beneficial reuse by 2035, including 174 million gallons per day of purified recycled water. These measures will help Los Angeles thrive in the drought-afflicted climate paradigm of the near future. The Hyperion sewage treatment plant is looking to add membrane bioreactor, reverse osmosis, and UV light disinfection capabilities to its processes.

Image credit: https://www.waterandwastewater.com/

Sludge Thickening

Sludge Thickening

Sludge Thickening

11/04/25

“Why do we need to add solids to wastewater before further treatment?”

Sludge treatment processes such as dewatering require conditioning before they can proceed. One of the first steps is to increase the solids concentration of sludge through Sludge Thickening. Sludge thickening ensures that the sludge is not too thin to handle in later processes. 

Image credit: https://aosts.com/

Soluble BOD

Soluble BOD

Soluble BOD

11/02/25

“How can we describe the portion of organic material that dissolves in water?”

BOD measures the amount of oxygen required to consume the organic matter present in a water sample. Some of the organic material, such as large chunks of food, is suspended and visible, while others are dissolved in the water itself. We can measure the BOD needed to consume the latter as Soluble BOD. Soluble BOD is easier to manage than the more visible, suspended, particulate BOD because of its smaller size.

Sludge Conditioning

Sludge Conditioning

Sludge Conditioning

11/01/25

“Why do we need to pretreat sludge before separating the water from the solids?”

Sludge is a mixture of solid waste and water. Sludge is processed by separating the solid waste from the water. However, sludge will require pre-treatment called Sludge Conditioning before dewatering to ensure successful processing. Sludge conditioning comes in numerous forms, ranging from aerobic digestion to thermal conditioning.

Image credit: https://www.waterexchemicals.com/

Sludge Volume Index

Sludge Volume Index

Sludge Volume Index

10/26/25

“How can we quantify the quality of sludge settlement?”

The settlement of sludge in a clarifier indicates treatment process effectiveness. We can quantify this effectiveness by finding the ratio between the volumetric density of sludge that settles (30-minute settled solid volume) and the total suspended solids in the sample (mixed liquor suspended solids) to obtain the Sludge Volume Index. Lower sludge volume indices indicate dense, well-contained settling, while higher values exemplify lower operational effectiveness.  

30-Minute Settled Sludge Volume (SSV30)

30-Minute Settled Sludge Volume (SSV30)

30-Minute Settled Sludge Volume (SSV30)

10/25/25

“How can we observe our secondary clarifier performance in a wastewater treatment plant?”

Wastewater treatment plants are the backbone of waste management in countless communities. Their operational performance may vary due to a variety of factors. One way we can test this is by taking a 1-liter sample of the mixed liquor from the system’s aeration tank, pouring it into a container through an Imhoff cone or graduated cylinder, and waiting for 30 minutes. Sludge will settle downwards during this time, coalescing into a quantity that can be measured, known as the 30-Minute Settled Sludge Volume, also referred to as the SSV30. SSV30 is a foundational component of measuring the Sludge Volume Index.

Sludge Retention Time

Sludge Retention Time

Sludge Retention Time

10/24/25

“How can we quantify the average amount of time microorganisms remain in a biological treatment system?”

Many wastewater treatment systems use microorganisms in sludge for treatment. However, these microorganisms will stay in the system only for a certain period of time. So, how can we determine how long, on average, these microorganisms will remain in these systems? Well, what if we were to take the mass of microorganisms present and divide it by the rate microorganisms leave the treatment system? This Sludge Retention Time governs wastewater treatment reactor behavior with the equation Sludge Retention Time = Volume of Reactor Chamber * Mixed Liquor Suspended Solids/(Waste Sludge Flow Rate * Waste Sludge Solids Concentration * Effluent Sludge Flow Rate * Effluent Sludge Solids Concentration). The effluent sludge solids concentration is frequently negligible, so the term is often taken out.

Food to Microorganism Mass Ratio

Food to Microorganism Mass Ratio

Food to Microorganism Mass Ratio

10/23/25

“How can we compare the amount of mass a wastewater treatment plant needs to clean versus the potential it can provide?”

Wastewater treatment plants will have to remove a certain amount of organic compounds, as quantified by the BOD loading rate. At the same time, they have a potential measured by the Mixed Liquor Suspended Solids multiplied by the volume. The ratio between these two variables measures the amount of waste that needs treatment versus the capabilities of the system, much like the “food” that needs to be consumed versus the “hunger levels” of the system. In fact, wastewater experts call this relationship the Food to Microorganism Mass Ratio in light of the metaphor.

Volumetric Substrate Loading Rate

Volumetric Substrate Loading Rate

Volumetric Substrate Loading Rate

10/22/25

“How can we quantify the amount of organic matter entering a reactor over a given amount of time and volume?”

Reactors treat water to make it usable for people. We can use the BOD loading rate to quantify how much organic matter is entering a reactor over a given time. However, we also might want to know how much treatment is necessary not just per time but also per volume to make it independent of reactor size. We can simply quantify this using the Volumetric Substrate Loading Rate, which is equal to a reactor’s BOD loading rate divided by its volume.