Formulas

Convert milligrams per liter (mg/L) of ammonia-nitrogen to pounds per million gallons (lb/MMG) of ammonia. Convert mg/L of NH3-N to pounds per liter by dividing by 454 (grams in a pound). Convert pounds per liter to lb/MMG by multiplying by 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). Convert mg/L to g/L by dividing by 1000. Multiply by the molecular weight of oxygen to get oxygen in g/L. Convert g/L to lb/MMG by multiplying by 8.34 (pounds per gallon). Multiply by the flow rate in MGD to get oxygen demand in lb/d.

Convert milligrams per liter (mg/L) of COD to pounds of oxygen demand per day (lb/d). Convert mg/L to g/L by dividing by 1000. Multiply by the molecular weight of oxygen to get oxygen in g/L. Convert g/L to lb/MMG by multiplying by 8.34 (pounds per gallon). Multiply by the flow rate in MGD to get oxygen demand in lb/d.

Convert colony-forming units (CFU) to other bacterial concentration units. CFU to cells/mL: 1 CFU is generally treated as approximately 1 bacterial cell (varies by organism and conditions). CFU to CFU/mL: same unit, no conversion needed. CFU to mg/L: Bacterial Concentration (mg/L) = (Number of CFUs) x (Average Weight of Bacterial Cell in pg) x (Density of Culture in cells/mL) / 10^9. CFU to cells/g: Bacterial Concentration (cells/g) = (Number of CFUs) / (Sample Weight in grams).

1 milligram = 0.00000220462 pounds; 1 liter = 0.264172 gallons; 1 million gallons = 1,000,000 gallons. Combined conversion factor: 1 mg/L = 0.000584177 lb/MMG. Concentration in lb/MMG = Concentration in mg/L x 0.000584177. Example: 100 mg/L x 0.000584177 = approximately 0.0584177 lb/MMG.

1 mg/L = 1 ppm.

Dilution Factor = [Initial Volume] / [Final Volume]

Percent Saturation = (DO Concentration / DO Saturation Value) x 100. DO Concentration is the dissolved oxygen concentration in mg/L. DO Saturation Value is the maximum dissolved oxygen water can hold at a given temperature and pressure, in mg/L.

F:M Ratio = [Organic Loading Rate (food)] / [Microorganism Population (microorganisms)]

1 liter = 0.000264172 gallons; 1 second = 86,400 seconds (for days). Conversion factor: 1 L/s = 0.000264172 MGD. Flow rate in MGD = Flow rate in L/s x 0.000264172. Example: 100 L/s x 0.000264172 = approximately 0.0264172 MGD.

1 cubic meter = 264.172 gallons; 1 second = 60 seconds (for minutes). Conversion factor: 1 m3/s = 264.172 GPM. Flow rate in GPM = Flow rate in m3/s x 264.172. Example: 0.5 m3/s x 264.172 = approximately 132.086 GPM.

Convert milligrams per liter (mg/L) to micrograms per liter (ug/L). Concentration in ug/L = Concentration in mg/L x 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. Convert mg/L of NO3-N to g/L by dividing by 1000. Multiply by the molecular weight of nitrogen to get nitrogen in g/L. Convert g/L to lb/MMG by multiplying by 8.34. Multiply by the flow rate in MGD to get nitrate in lb/d.

Convert milligrams per liter (mg/L) of oil and grease to pounds per million gallons (lb/MMG). Convert mg/L to pounds per liter by dividing by 454. Convert pounds per liter to lb/MMG by multiplying by 1000 and then by the flow rate in MGD.

[H+] = 10^(-pH). [H+] is the hydrogen ion concentration in moles per liter (mol/L); pH is the pH value of the solution. Calculate 10 raised to the negative pH value to get [H+]. Example: pH of 3 gives [H+] = 10^(-3) = 0.001 mol/L.

Convert milligrams per liter (mg/L) of phosphorus to pounds per million gallons (lb/MMG) of phosphorus. Convert mg/L to g/L by dividing by 1000. Multiply by the atomic weight of phosphorus to get phosphorus in g/L. Convert g/L to lb/MMG by multiplying by 8.34. Multiply by the flow rate in MGD to get phosphorus in lb/d.

Convert milliliters per liter (mL/L) to milligrams per liter (mg/L). 1 mL/L = 1 mg/L.

Convert milligrams per liter (mg/L) of TDS to parts per million (ppm). 1 mg/L (TDS) = 1 ppm (TDS).

F = (C x 9/5) + 32. Multiply the Celsius temperature by 9/5 (1.8), then add 32.

Convert milligrams per liter (mg/L) of TSS to pounds per million gallons (lb/MMG). Convert mg/L to pounds per liter by dividing by 454. Convert pounds per liter to lb/MMG by multiplying by 1000 and then by the flow rate in MGD.

Backwashing cleans the filter media; backwash rate is the rate at which water flows in the reverse direction during backwashing. Backwash Rate = (Flow Rate) / (Backwash Time).

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).

Detention time is the average time water spends within the multimedia filter. Detention Time = (Volume of Filter Bed) / (Flow Rate).

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).

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 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] x 100.

Porosity is the fraction of the media bed volume 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).

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 x Feed Concentration).

Rejection rate represents the percentage of contaminants removed by the NF membrane. Rejection Rate (%) = [(Initial Concentration – Final Concentration) / Initial Concentration] x 100.

Retention is the percentage of solutes 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 NF membrane’s ability to separate different solutes. Selectivity = (Rejection of Solute A) / (Rejection of Solute B).

TMP is the pressure difference across the NF membrane that drives permeate flow. TMP = (Inlet Pressure) – (Outlet Pressure).

The removal efficiency of a slant plate clarifier for suspended solids, based on influent and effluent concentrations. Efficiency (%) = [(Influent Concentration – Effluent Concentration) / Influent Concentration] x 100.

The flow rate through a slant plate clarifier, an important parameter for design and operation that helps determine hydraulic loading. Flow Rate (Q) = [Volume of Clarifier (V)] / [Time (t)].

The angle of inclination of the plates affects settling behavior. Common angles range from 45 to 60 degrees. All J Mark Clarifiers are angled at 55 degrees.

The number of inclined plates in the clarifier impacts the available settling area and 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 (theta) = [Volume of Clarifier (V)] / [Flow Rate (Q)].

Sludge volume is an important factor for sludge handling and disposal. Sludge Volume = [Sludge Concentration (C)] x [Volume of Settled Sludge].

The surface area of the inclined plates is key to slant plate clarifier design, influencing settling efficiency. Effective Settling Area (A) = [Number of Plates (N)] x [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)].

Flux is the rate of water flow through the RO membrane per unit area. Flux = (Permeate Flow Rate) / (Membrane Area).

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 water passage through the membrane due to differences in solute concentration. Osmotic Pressure = (pi x C) / 2, where pi 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 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)] x 100.

Rejection rate refers to the percentage of contaminants removed by the RO membrane. Rejection Rate (%) = [(Initial Concentration – Final Concentration) / Initial Concentration] x 100.

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 (%).