Category: Biology

Hazard Quotient

Hazard Quotient

01/27/26

“How can we quantify the lethality of exposure to a substance?”

People are exposed to potentially hazardous substances all the time, whether it’s traces of air pollution or bacterial growth on food. We also know that if exposure breaches a certain level, it becomes dangerous. So how can we quantify the lethality of exposure to a substance? Well, what if we divide the exposure level by the reference dose? This is how the Hazard Quotient works, and it is a very useful tool in toxicology.

Noise Dose

Noise Dose

01/24/26

“How can we quantify the level of noise someone is exposed to over time?”

Listening to too much loud noise is a well-known safety risk. The constant vibration in your ears can lead to long-term damage if not managed properly. The Noise Dose quantifies how much noise a person has been exposed to for the day, regarding safety levels. We can quantify noise dose by taking the hours someone listened to a certain decibel of noise and dividing it by the maximum number of hours it’s safe to listen to that noise level per day. We can sum this ratio for every noise decibel level heard throughout the day, multiplied by 100% to arrive at the total noise dose. If a noise dose exceeds 100 percent, then the person has breached the healthy recommended daily noise levels.

Chronic Daily Intake

Chronic Daily Intake

01/23/26

“How can we calculate the amount of contaminant a person is exposed to daily?”

People are exposed to all kinds of substances throughout the day, whether it’s from the food we eat or the air we breathe. Some of these substances are harmful and can lead to health problems. We can measure how much of these contaminants we expose ourselves daily through Chronic Daily Intake. Chronic daily intake is typically expressed as milligrams of substance per kilogram of body weight per day. The US E.P.A uses chronic daily intake as part of health hazard assessment.

Acceptable Daily Intake (ADI)

Acceptable Daily Intake (ADI)

01/21/2026

“How does the WHO measure how much a certain substance in food or drinking water can be consumed daily over a lifetime without an appreciable health risk?”

NOAELs document how much of a substance an organism can handle before a statistically significant health effect occurs. However, these studies may be conducted in controlled environments or on test animals that may not accurately reflect human conditions. To account for all of these variables, organizations such as the World Health Organization (WHO) and the European Food Safety Authority (EFSA) use Acceptable Daily Intake (ADI). Acceptable daily intake measures the amount of a certain substance in food or drinking water that can be consumed daily over a lifetime without an appreciable health risk to people. This is commonly expressed as milligrams of substance per kilogram of body weight and is applied by regulatory and health authorities all over the world to monitor food additives, pesticides, and much more. Acceptable daily intake is applied to food ingredients similar to how reference dose is applied to environmental toxins.

Reference Dose (RfD)

Reference Dose (RfD)

01/20/26

“How does the U.S. EPA produce recommended daily lifetime exposure limits for substances?”

NOAELs are the highest level of a substance a person can take without any statistically significant effects, according to research. However, this could be much higher than what may actually be safe for long-term use. The U.S. EPA has created the Reference Dose (RfD) in response. Reference does are the maximum acceptable oral dose of a toxic substance that has no adverse noncancer health effects from a lifetime of exposure. Reference doses are commonly found by dividing the NOAEL for a substance by uncertainty factors.

NOAEL – No Observed Adverse Effect Level

NOAEL – No Observed Adverse Effect Level

01/19/26

“How can we measure the highest dose of a substance that does not cause any statistically significant effect?”

People worry about whether a substance they’re exposed to leads to health complications. One way to understand this is to measure the highest dosage of the substance that organisms can handle before a statistically significant effect occurs. Labeled NOAEL – No Observed Adverse Effect Level, these measurements are fundamental for quantifying safe exposure levels for substances.

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.

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Biological Yield (Wastewater Treatment)

Biological Yield (Wastewater Treatment)

10/31/25

“How can we quantify how much microorganism biomass increases given a certain amount of organic material in a wastewater treatment plant?”

Microorganisms consume organic material from BOD Loading to create more microorganism mass. The amount of microorganism mass created per a given substrate concentration, also known as the Biological Yield, is governed by the equation Y = dX/dS, Where Y is the biological yield (measured in mg Vss/mg BOD), dX the increase in biomass concentration (mg/L), and dS the decrease in substrate concentration (mg/L). The higher a wastewater treatment system’s yield, the higher its ability to handle sludge

Stabilization Ponds

Stabilization Ponds

10/27/25

“How can we use ponds to treat wastewater?”

It’s common for people to associate “modern” wastewater treatment with towering industrial plants that look like they’re straight out of a Martian civilization. But what if I told you that ponds could also serve as effective wastewater treatment? Essentially, ponds can have bacteria that consume the organic matter in wastewater, producing cleaner effluent and carbon dioxide. Algae in the pond can absorb the CO2 and transform it into oxygen to feed the organic-matter-eating bacteria. These systems, known as Stabilization Ponds, are incredible for low-energy, high-land availability communities often found in numerous developing countries.

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