water consulting - industrial wastewater treatment

Industrial Water Treatment FAQ's

K2O Consulting is here to answer any of your industrial wastewater treatment related questions. The follow is a list of commonly asked questions and answers. If you question is not listed below, feel free to contact us with your question for a prompt answer!

Oil/Water Separation FAQ's

Q) What is the difference between "free oil" and "dissolved oil"?

A) Free oil is oil that will settle to the top of water given a reasonable amount of time. Free oil is in droplet form and coalesces with other oil droplets upon contact with each other. This coalescing enhances the oil separation process based on Stokes Law. Dissolved oil is not in droplet form and will not rise to the top of water regardless of the amount of time that it is immersed with the water. Dissolved oil stays in solution with the water indefinitely.

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Q) What factors are important in sizing an oil/water separator?

A) Temperature of the water, viscosity of the water, specific gravity of the oil in the water, knowledge of the oil droplet size amount of suspended solids present. All of these parameters must be considered when selecting the size and type of oil/water separation equipment to be used.

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Q) Why is it important to know the difference between free oil and dissolved oil present in a waste stream?

A) It is very important to know if there is dissolved oil in a waste stream. That is because dissolved oil will pass through a media type filter or oil/water separator such as dissolved air flotation, dissolved gas flotation, API separator or lamella type oil/water separator. Dissolved oil must be chemically treated to break any emulsion prior to being treated with the equipment described above. Otherwise, a different technology must be used.

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Reverse Osmosis FAQ's

Q) How do I know if pretreatment will be required in front of a reverse osmosis (RO) system being used for boiler feed water?

A) A common oversight in designing reverse osmosis systems is the Silt Density Index of the water to be fed to the RO system. RO membranes have a fine porosity and are susceptible to fine particles called silt which may not be apparently visible. This is a relatively simple and short test that can prevent frequent RO membrane cleanings and even membrane fouling. It is especially important to test river water and is also recommended to test city water intended to be used for boiler feed water. Once the silt density index is known, an experienced water treatment company or consultant can recommend the type of pretreatment that will be required.

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Q) Why is it important to have a complete and balanced water analysis prior to sizing a reverse osmosis (RO) system?

A) A complete and balanced water analysis should always be done prior to sizing an RO system. The anions and cations should add up to zero. With this balanced water analysis, a computer model can be run which will determine the number and array of RO membranes required. It will also determine the rejection rate of the RO membranes which is important in determining if the RO system will provide the desired water quality. 

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Q) What are two proven methods of removing nitrates from water?

A) Ion exchange and reverse osmosis (RO) have been proven to effectively remove nitrates from water down to safe drinking levels. Ion exchange is selective so, only the nitrates are removed while other ions pass through the system. Removal efficiencies of 95-99% are possible with ion exchange. Reverse osmosis will also provide similar removal efficiencies but will remove other ions in the water along with the nitrates.

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Media Filtration FAQ's

Q) For media filtration, why is it important to have a particle size distribution of the suspended solids?

A) Different types of media filters produce different porosity or interstices sizes. Media filters work best when the particle size distribution is “normal”. That means there are particles of various sizes in various concentrations. In this way, the particles themselves can enhance removal and increase the efficiency of the media filter. If the particle size distribution shows that many of the particles are fine and make up most of the concentration, a media filter may not effectively remove those particles.

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Q) Why is walnut shell filtration effective for free oil removal?

A) Black walnut shells have been known to have an affinity for oil for a long time. Pulverized walnut shells are used in the cosmetic industry to take oil off skin. Walnut shell media is adsorbent to oil, meaning that the free oil will adhere to the surface of the media but not be absorbed into the media. This allows for cleaning and regeneration of the media. Walnut shell media has the proper hardness and modulus of elasticity which enable it to have an attrition rate of only 7% per year.

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Biological FAQ's

Q) How do I know if simple flotation type separators will reduce Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) down to acceptable discharge limits?

A) Biochemical Oxygen Demand (BOD) and Chemical Oxygen Demand (COD) can be in two states in water. They can be dissolved in the water or they can be residual with organics. Obtaining an analysis for total BOD and COD will not be enough to determine if a flotation separator will remove enough of the BOD and COD to meet discharge limits. An analysis for free and dissolved BOD and COD must be done in order to determine if flotation separation is sufficient or, if further biological treatment will be required.

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River Water Filtration FAQ's

Q) Can a micro filter be used in place of a clarifier for river water filtration?

A) Yes, a micro filter can be used in place of a conventional clarifier. This is a growing trend because of the space savings and lower operational costs. Note that turbidity of the river water should be measured in NTU’s (Nephelometric Turbidity Units) prior to sizing the micro filters. Measuring the turbidity will help in determining the rejection rate of the micro filter and hence, provide an accurate permeate flow rate.

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