Water Formulas

Contact us

Water Quality Conversion Chart

Common Formulas

  • Convert milligrams per liter (mg/L) of ammonia-nitrogen to pounds per million gallons (lb/MMG) of ammonia.

    1. Convert mg/L of NH3-N to pounds per liter by dividing by 454, since there are 454 grams in a pound.

    2. Convert pounds per liter to pounds per million gallons (lb/MMG) by multiplying by a factor of 1000 (since there are 1000 liters in a cubic meter) and then by the flow rate in million gallons per day (MGD).

  • Convert milligrams per liter (mg/L) of BOD to pounds of oxygen demand per day (lb/d).

    1. Convert mg/L to grams per liter (g/L) by dividing by 1000 (since there are 1000 milligrams in a gram).

    2. Multiply the result by the molecular weight of oxygen to get the amount of oxygen in grams per liter.

    3. Convert grams per liter to pounds per million gallons (lb/MMG) by multiplying by a factor of 8.34 (since there are 8.34 pounds in a gallon).

    4. Multiply the result by the flow rate in million gallons per day (MGD) to get the oxygen demand in pounds per day.

  • Convert milligrams per liter (mg/L) of COD to pounds of oxygen demand per day (lb/d).

    1. Convert mg/L to grams per liter (g/L) by dividing by 1000 (since there are 1000 milligrams in a gram).

    2. Multiply the result by the molecular weight of oxygen to get the amount of oxygen in grams per liter.

    3. Convert grams per liter to pounds per million gallons (lb/MMG) by multiplying by a factor of 8.34 (since there are 8.34 pounds in a gallon).

    4. Multiply the result by the flow rate in million gallons per day (MGD) to get the oxygen demand in pounds per day.

  • Convert colony-forming units (CFU) to other bacterial concentration units.

    1. CFU to Cells per Milliliter (cells/mL): In many cases, CFU and bacterial cells are used interchangeably. So, you can often consider 1 CFU as approximately equivalent to 1 bacterial cell. However, keep in mind that this might not hold true for all types of bacteria and growth conditions.

    2. CFU to Colony-forming units per milliliter (CFU/mL): This is the same unit as CFU. No conversion is needed.

    3. CFU to Bacterial Concentration in milligrams per liter (mg/L): Converting CFU to mg/L is more complex, as it depends on the specific bacteria, their weight, and the medium they are grown in. Generally, the conversion requires knowing the average weight of a bacterial cell in picograms (pg) and the density of the bacterial culture. The formula would be:

    Bacterial Concentration (mg/L) = (Number of CFUs) × (Average Weight of Bacterial Cell in pg) × (Density of Culture in cells/mL) / 10^9

    4. CFU to Bacterial Concentration in cells per gram (cells/g): This conversion involves knowing the mass of the sample and the number of CFUs on that sample. The formula is: Bacterial Concentration (cells/g) = (Number of CFUs) / (Sample Weight in grams)

  • Convert milligrams per liter (mg/L) to parts per million (ppm).

    1. 1 mg/L = 1 ppm

    Convert milligrams per liter (mg/L) to pounds per million gallons (lb/MMG).

    1. 1 milligram = 0.00000220462 pounds 1 liter = 0.264172 gallons 1 million gallons = 1,000,000 gallons

    2. So, the combined conversion factor is: 1 mg/L = 0.00000220462 pounds per liter (lb/L) 1 mg/L = 0.00000220462 pounds per liter (lb/L) × 0.264172 liters per gallon × 1,000,000 gallons per million gallons 1 mg/L = 0.000584177 lb/MMG

    3. To convert a concentration from milligrams per liter to pounds per million gallons, you would multiply the concentration in mg/L by the conversion factor:

    4. Concentration in lb/MMG = Concentration in mg/L × 0.000584177

    5. For example, if you have a concentration of 100 mg/L, you can convert it to pounds per million gallons as follows:

    6. Concentration in lb/MMG = 100 mg/L × 0.000584177 ≈ 0.0584177 lb/MMG

    7. Therefore, a concentration of 100 mg/L is approximately equivalent to 0.0584177 pounds per million gallons.

  • Dilution factor= [initial volume]/[final volume]

  • Convert milligrams per liter (mg/L) of dissolved oxygen to percent saturation.

    Percent Saturation = (DO Concentration / DO Saturation Value) × 100

    Where:

    1. DO Concentration is the dissolved oxygen concentration in milligrams per liter (mg/L).

    2. DO Saturation Value is the maximum amount of dissolved oxygen that can be held in water at a given temperature and pressure, usually expressed in mg/L.

  • Convert cubic meters per second (m³/s) to gallons per minute (GPM).

    1. 1 cubic meter = 264.172 gallons 1 second = 60 seconds (for minutes)

    2. So, the conversion factor is: 1 m³/s = 264.172 GPM

    3. To convert a given flow rate from cubic meters per second to gallons per minute, simply multiply the flow rate in cubic meters per second by the conversion factor:

    4. Flow rate in GPM = Flow rate in m³/s × 264.172

    5. For example, if you have a flow rate of 0.5 cubic meters per second, you can convert it to gallons per minute as follows:

    6. Flow rate in GPM = 0.5 m³/s × 264.172 = 132.086 GPM

    7. Therefore, a flow rate of 0.5 cubic meters per second is approximately equivalent to 132.086 gallons per minute.

    Convert liters per second (L/s) to million gallons per day (MGD).

    1. 1 liter = 0.000264172 gallons 1 second = 86,400 seconds (for days)

    2. So, the conversion factor is: 1 L/s = 0.000264172 MGD

    3. To convert a flow rate from liters per second to million gallons per day, you would multiply the flow rate in liters per second by the conversion factor:

    4. Flow rate in MGD = Flow rate in L/s × 0.000264172

    5. For example, if you have a flow rate of 100 liters per second, you can convert it to million gallons per day as follows:

    6. Flow rate in MGD = 100 L/s × 0.000264172 ≈ 0.0264172 MGD

    7. Therefore, a flow rate of 100 liters per second is approximately equivalent to 0.0264172 million gallons per day.

  • F:M Ratio= [organic loading rate (food)] / [microorganism population (microorganisms)]

  • Convert milligrams per liter (mg/L) to micrograms per liter (µg/L).

    1. Concentration in μg/L=Concentration in mg/L×1000

  • HRT= [volume of treatment system (V)] / [Flow rate (Q)]

  • Convert milligrams per liter (mg/L) of nitrate-nitrogen to pounds per million gallons (lb/MMG) of nitrate.

    1. Convert mg/L of NO3-N to grams per liter (g/L) by dividing by 1000 (since there are 1000 milligrams in a gram).

    2. Multiply the result by the molecular weight of nitrogen to get the amount of nitrogen in grams per liter.

    3. Convert grams per liter to pounds per million gallons (lb/MMG) by multiplying by a factor of 8.34 (since there are 8.34 pounds in a gallon).

    4. Multiply the result by the flow rate in million gallons per day (MGD) to get the nitrate in pounds per day.

  • Convert milligrams per liter (mg/L) of oil and grease to pounds per million gallons (lb/MMG).

    1. Convert mg/L of oil and grease to pounds per liter by dividing by 454, since there are 454 grams in a pound.

    2. Convert pounds per liter to pounds per million gallons (lb/MMG) by multiplying by a factor of 1000 (since there are 1000 liters in a cubic meter) and then by the flow rate in million gallons per day (MGD).

  • Convert pH values to hydrogen ion concentration (H+).

    [H+] = 10^(-pH)

    1. [H+] is the hydrogen ion concentration in moles per liter (mol/L).

    2. pH is the pH value of the solution.

    Here's how to perform the conversion:

    1. Calculate 10 raised to the power of the negative pH value.

    2. The result will give you the hydrogen ion concentration in moles per liter.

    For example, if you have a solution with a pH of 3:

    [H+] = 10^(-3) [H+] = 0.001 mol/L

    So, a solution with a pH of 3 has a hydrogen ion concentration of 0.001 mol/L.

  • Convert milligrams per liter (mg/L) of phosphorus to pounds per million gallons (lb/MMG) of phosphorus.

    1. Convert mg/L of phosphorus to grams per liter (g/L) by dividing by 1000 (since there are 1000 milligrams in a gram).

    2. Multiply the result by the atomic weight of phosphorus to get the amount of phosphorus in grams per liter.

    3. Convert grams per liter to pounds per million gallons (lb/MMG) by multiplying by a factor of 8.34 (since there are 8.34 pounds in a gallon).

    4. Multiply the result by the flow rate in million gallons per day (MGD) to get the phosphorus in pounds per day.

  • Convert milliliters per liter (mL/L) to milligrams per liter (mg/L).

    1. 1 mL/L = 1 mg/L

  • Convert degrees Celsius (°C) to degrees Fahrenheit (°F).

    °F = (°C × 9/5) + 32

    1. Multiply the Celsius temperature by 9/5 (which is 1.8).

    2. Add 32 to the result.

  • Convert milligrams per liter (mg/L) of TDS to parts per million (ppm).

    1. 1 mg/L (TDS) = 1 ppm (TDS)

  • Convert milligrams per liter (mg/L) of TSS to pounds per million gallons (lb/MMG).

    1. Convert mg/L to pounds per liter by dividing by 454, since there are 454 grams in a pound.

    2. Convert pounds per liter to pounds per million gallons (lb/MMG) by multiplying by a factor of 1000 (since there are 1000 liters in a cubic meter) and then by the flow rate in million gallons per day (MGD).

Slant Plate Clarifier Formulas

  • The removal efficiency of a slant plate clarifier for suspended solids can be calculated based on influent and effluent concentrations.

    Efficiency (%) = [(Influent Concentration - Effluent Concentration) / Influent Concentration] × 100

    Calculator

  • The flow rate through a slant plate clarifier is an important parameter for design and operation. It helps determine the hydraulic loading on the clarifier.

    Flow Rate (Q) = [Volume of Clarifier (V)] / [Time (t)]

    Calculator

  • The angle of inclination of the plates affects the settling behavior. Common angles range from 45 to 60 degrees.

    All J Mark Clarifiers are angled at 55 degrees.

    Calculator

  • The number of inclined plates in the clarifier impacts the available settling area and thus the overall performance.

    Number of Plates (N) = [Effective Settling Area (A)] / [Plate Area (A_plate)]

  • Overflow rate is a measure of the solids loading on the clarifier's effluent.

    Overflow Rate = [Flow Rate (Q)] / [Surface Area of Clarifier (A)]

  • Retention time is the average time wastewater spends in the clarifier, affecting settling efficiency.

    Retention Time (θ) = [Volume of Clarifier (V)] / [Flow Rate (Q)]

    Calculator

  • Sludge volume is an important factor for sludge handling and disposal.

    Sludge Volume = [Sludge Concentration (C)] × [Volume of Settled Sludge]

  • The surface area of the inclined plates is a key factor in the design of slant plate clarifiers as it influences settling efficiency. The following formula provides an estimate of the effective settling area:

    Effective Settling Area (A) = [Number of Plates (N)] × [Plate Area (A_plate)]

  • Surface overflow rate is a measure of the hydraulic loading on the clarifier and impacts its performance.

    Surface Overflow Rate = [Flow Rate (Q)] / [Effective Settling Area (A)]

Nanofiltration Formulas

  • CP refers to the accumulation of solutes near the membrane surface due to permeate flow.

    CP = (Feed Concentration) - (Concentration at Membrane Surface)

  • Flux is the rate of permeate flow through the NF membrane per unit area.

    Flux = (Permeate Flow Rate) / (Membrane Area)

  • Membrane area is an important design parameter for NF systems.

    Membrane Area = (Permeate Flow Rate) / (Flux)

  • Normalized permeate flow rate accounts for variations in feed concentration and pressure.

    Normalized Permeate Flow Rate = (Permeate Flow Rate) / (TMP × Feed Concentration)

  • Similar to reverse osmosis, nanofiltration also has a rejection rate, which represents the percentage of contaminants removed by the NF membrane.

    Rejection Rate (%) = [(Initial Concentration - Final Concentration) / Initial Concentration] × 100

  • Retention is the percentage of solutes that are retained by the NF membrane.

    Retention (%) = 100 - Rejection Rate (%)

  • Salt passage represents the percentage of salts that pass through the NF membrane and remain in the permeate.

    Salt Passage (%) = 100 - Rejection Rate (%)

  • Selectivity measures the ability of the NF membrane to separate different solutes.

    Selectivity = (Rejection of Solute A) / (Rejection of Solute B)

  • TMP is the pressure difference across the NF membrane that drives the permeate flow.

    TMP = (Inlet Pressure) - (Outlet Pressure)

Reverse Osmosis Formulas

  • Flux is the rate of water flow through the RO membrane per unit area.

    Flux = (Permeate Flow Rate) / (Membrane Area)

    Calculator

  • NDP is the pressure difference that drives water through the RO membrane.

    NDP = (Inlet Pressure) - (Osmotic Pressure) - (Pressure Drop)

  • Osmotic pressure is the pressure required to prevent the passage of water through the membrane due to differences in solute concentration.

    Osmotic Pressure = (π × C) / 2

    where π is the osmotic coefficient (typically 0.95-0.98) and C is the molar concentration of dissolved solids.

  • Pressure drop across the RO membrane is influenced by factors such as flow rate, membrane fouling, and feedwater quality.

    Pressure Drop = (Inlet Pressure) - (Outlet Pressure)

  • Recovery rate is the percentage of feedwater that becomes permeate (product water) through the RO process.

    Recovery Rate (%) = [(Permeate Flow Rate) / (Feed Flow Rate)] × 100

    Calculator

  • Rejection rate refers to the percentage of contaminants removed by the RO membrane.

    Rejection Rate (%) = [(Initial Concentration - Final Concentration) / Initial Concentration] × 100

    Calculator

  • SCP refers to the concentration increase of salts near the membrane surface due to permeate flow.

    SCP = (Feed Concentration) - (Concentration at Membrane Surface)

  • Salt passage represents the percentage of salts that pass through the RO membrane and remain in the permeate.

    Salt Passage (%) = 100 - Rejection Rate (%)

  • Salt rejection is another way to express the removal of salts by the RO membrane.

    Salt Rejection (%) = 100 - Salt Passage (%)

Multimedia Filtration Formulas

  • Backwashing is an essential step in multimedia filtration to clean the filter media. Backwash rate is the rate at which water flows in the reverse direction during backwashing.

    Backwash Rate = (Flow Rate) / (Backwash Time)

    Calculator

  • Bed expansion is the increase in the volume of the media bed during backwashing.

    Bed Expansion = [(Bed Volume during Backwash) - (Bed Volume during Filtration)] / (Bed Volume during Filtration)

    Calculator

  • Detention time is the average time water spends within the multimedia filter.

    Detention Time = (Volume of Filter Bed) / (Flow Rate)

    Calculator

  • Filtration rate is the rate at which water flows through the multimedia filter per unit area of the filter bed.

    Filtration Rate = (Flow Rate) / (Filter Bed Area)

    Calculator

  • Head loss is the pressure drop across the filter bed due to the flow of water through the media.

    Head Loss = (Initial Pressure) - (Final Pressure)

  • The depth of the media bed in the filter affects the filtration efficiency.

    Media Depth = (Volume of Filter Bed) / (Filter Bed Area)

  • Particle removal efficiency indicates the effectiveness of the multimedia filter in removing suspended particles.

    Particle Removal Efficiency (%) = [(Influent Particle Concentration - Effluent Particle Concentration) / Influent Particle Concentration] × 100

  • Porosity is the fraction of the media bed volume that is occupied by voids or pores.

    Porosity = (Void Volume) / (Total Volume)

  • Surface overflow rate is a measure of the hydraulic loading on the filter bed.

    Surface Overflow Rate = (Flow Rate) / (Filter Bed Area)