Solids, liquids, and gases may dissolve in water to form solutions. The amount of solute present may vary below certain limits, so-called solubility. The strength of a solution can be expressed in two ways:

(1) weight (lb) of active solute per 100 pounds (i.e. %) and

(2) weight of active solute per unit volume (gallons or liters) of water.

Either expression can be computed to the other if the density or specific gravity is known. If the solution is dilute (less than 1%), the specific gravity can be assumed to be 1.0; i.e. 1 L of solution is equal to 1 kg and 1 gal of solution equals 8.34 lb.
In water chemistry, molarity is defined as the number of gram-molecular weights or moles of substance present in a liter of the solution. If solutions have equal molarity, it means that they have an equal number of molecules of dissolved substance per unit volume. The weight of substance in the solution can be determined as follows:
The molarity (M) of a solution can be expressed as:

M (mol/L) = moles of solute (mole) / 1.0 L of solution

For uniform purpose,

the Normality (N) is used for preparation of laboratory solutions. The
normality can be written as:
    N (eq/L or meq/L) = equivalent of solute (eq or meq) / 1.0 L of solution

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Integrity Test is very essential to evaluate whether the module/element’s present state is good or it is going to end of life. Integrity Test is really means of fiber repair procedure.

The test is very useful for OUT to IN Flow style element Like DOW and Hyflux

Requirement:

You will need the following to complete the fiber repair

procedure:

• Concentrate tube plug

• Air supply apparatus

• Oil-free compressed air [recommended pressure: 3.0 bars (44 psi)]

• Loctite 406 glue

• Repair pins

• Personal protection equipment (gloves, safety glasses, etc.)

• Knife or diagonal cutters

Figure 1. Integrity test Feed Valve (OFF)Con. Valve (OFF)Air Inlet Valve (ON) PI Transparent TubePermeate Valve (ON)Observe whether air bubbles continuously appear

Procedure:

The bubble test using transparent tubes has been selected to illustrate how it is done.

1. Take the module out of the filtration mode.

2. Drain the module from the feed side.

3. Close feed and concentrate valve and keep the permeate valve open.

4. Pressurize the drained side of the module with oil-free compressed air from the air inlet valve, and slowly raise the air pressure to 1.5 bars (21 psi). Some displaced water will flow out the permeate side.

5. If large continuous air bubbles appear in the transparent tube then the module has broken fibers. Smaller and infrequent bubbles are the result of air diffusion through the pores of the ultrafiltration membrane. If leaks are confirmed, move to STEP 2.

Step-2

1. Drain the module from the feed side.

2. Remove the top end cap. Keep the bottom end cap on.

3. Isolate the module to perform repair by closing valves or sealing remaining openings.

4. Place the positioning block into the concentrate outlet tube. Then put in the fastening nut. Next, put in the cylinder block and screw in the fastening bolt. [Positioning block, fastening nut, cylinder block and fastening bolt are part of the concentrate tube plug assembly.]

5. Connect the air supply line.

6. Supply oil-free compressed air to the module and slowly raise pressure to 1.5 bars (or 21 psi). 7. Provide a water stream to cover the permeate end of the fibers to help locate any leaks.

8. As the air pressure rises, continuous air bubbles will appear at the location of a broken fiber. Mark the broken fiber with a pin.

9. Continue applying air and water until all broken fibers are located and marked.

10. Depressurize the module using the air release valve.

11. If the broken fibers are near the concentrate tube plug then remove the concentrate tube plug to provide room for repair.

12. Take a new repair pin and place a drop of glue on the end of the pin. Use it to replace the fiber- marking pin immediately. Push the pin firmly into the leaking fiber. Let the repair cure for 5 minutes before trimming the extruding portion of the pin with a knife or diagonal cutters. Repeat for all broken fibers.

13. Repeat steps 4 - 8 to make sure all broken fibers are repaired.

14. To complete the repair, depressurize the membrane, remove the concentrate tube plug, and reassemble the top end cap, remove seals, and realign valves for operation.

You have successfully repaired a Ultrafiltration module!

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Trickling filters are sometimes classified by the organic loading rate applied. The organic loading rate is expressed as a certain amount of BOD applied to a certain volume of media. In other words, the organic loading is defined as the pounds of BOD or chemical oxygen demand (COD) applied per day per 1000 cubic feet of media — a measure of the amount of food being applied to the filter slime.

To calculate the organic loading on the trickling filter, two things must be known: the pounds of BOD or COD being applied to the filter media per day and the volume of the filter media in units of 1000 cubic feet. The BOD and COD contribution of the recirculated flow is not included in the organic loading.

Example:

A trickling filter that is 60 ft in diameter receives a primary effluent flow rate of 0.440 MGD.Calculate the organic loading rate in units of pounds of BOD applied per day per 1000 ft3 of media volume. The primary effluent BOD concentration is 80 mg/L. The media depth is 9 ft.

0.440 MGD x 80 mg/L x 8.34 lb/gal = 293.6 lb of BOD applied/d
Surface area = 0.785 x (60)2 = 2826 ft 2
Area x depth x volume = cu ft
2826 ft2 x9 ft = 25,434 cu ft (TF volume)

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CHLORINE DISINFECTION

Chlorine deactivates microorganisms through several mechanisms that can destroy most biological contaminants, including:

• Damaging the cell wall 
• Altering the permeability of the cell (the ability to pass water in and out through the cell wall) • Altering the cell protoplasm
• Inhibiting the enzyme activity of the cell so it is unable to use its food to produce energy
• Inhibiting cell reproduction. 

Chlorine is supplied as a gas, liquid and a solid / Granular / Tablet.

  

Chlorine as GAS                          LIQUID                                    SOLID / TABLET

The gas is 100 percent elemental chlorine (Cl2), and is supplied in 150 lb. cylinders (10 inches in diameter and about 55 inches high) and in 2,000 lb. (ton) containers (30 inches in diameter and 82 inches high). The liquid is sodium hypochlorite (NaOCl) commonly used as laundry bleach. And the solid is calcium hypochlorite [Ca(OCl)2], available in granular form or as tablets.

Chlorine is available in a number of different forms: (1) as pure elemental gaseous chlorine (a greenish-yellow gas possessing a pungent and irritating odor that is heavier than air, nonflammable, and nonexplosive), which, when released to the atmosphere, is toxic and corrosive; (2) as solid calcium hypochlorite (in tablets or granules); or (3) as a liquid sodium hypochlorite solution (in various strengths). The strength of one form of chlorine compared to the others that must be used for a given water system depends on the amount of water to be treated, configuration of the water system, local availability of the chemicals, and skill of the operator. One of the major advantages of using chlorine is the effective residual that it produces. A residual indicates that disinfection is completed, and the system has an acceptable bacteriological quality. Maintaining a residual in the distribution system helps to prevent regrowth of those microorganisms that were injured but not killed during the initial disinfection stage.

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Water filtration is a physical process of separating suspended and colloidal particles from waste by passing the water through a granular material. The process of filtration involves straining, settling, and adsorption. As floc passes into the filter, the spaces between the filter grains become clogged, reducing this opening and increasing removal. Some material is removed merely because it settles on a media grain. One of the most important processes is adsorption of the floc onto the surface of individual filter grains. In addition to removing silt and sediment, flock, algae, insect larvae, and any other large elements, filtration also contributes to the removal of bacteria and protozoans such as Giardia lamblia and Cryptosporidium . Some filtration processes are also used for iron and manganese removal.

The surface water treatment rule (SWTR) specifies four filtration technologies, although SWTR also allows the use of alternate filtration technologies (e.g., cartridge filters). These include slow sand filtration see Figure, rapid sand filtration, pressure filtration, diatomaceous earth filtration, and direct filtration. Of these, all but rapid sand filtration is commonly employed in small water systems that use filtration. Each type of filtration system has advantages and disadvantages. Regardless of the type of filter, however, filtration involves the processes of straining (where particles are captured in the small spaces between filter media grains), sedimentation (where the particles land on top of the grains and stay there), and adsorption (where a chemical attraction occurs between the particles and the surface of the media grains).

FLOW RATE THROUGH A FILTER (gpm)

Flow rate in gpm through a filter can be determined by simply converting the gpd flow rate indicated on the flow meter. The flow rate (gpm) can be calculated by taking the meter flow rate (gpd) and dividing by 1440 min/day, as shown in Equation.

Flow rate gpm=flow rate (gpd) / 1440 min/day

• gpm:gallon per minute
• gpd:gallon per day

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Coagulation:Following screening and the other pretreatment processes, the next unit process in a conventional water treatment system is mixing, when chemicals are added during what is known as coagulation. The exception to this situation occurs in small systems using groundwater, where chlorine or other taste and odor control measures are often introduced at the intake and are the extent of treatment. The term coagulation refers to the series of chemical and mechanical operations by which coagulants are applied and made effective.

These operations are comprised of two distinct phases: (1) rapid mixing to disperse coagulant chemicals by violent agitation into the water being treated, and (2) flocculation to agglomerate small particles into well-defined floc by gentle agitation for a much longer time. The coagulant must be added to the raw water and perfectly distributed into the liquid; such uniformity of chemical treatment is reached through rapid agitation or mixing. Coagulation results from adding salts of iron or aluminum to the water and is a reaction between one of the following (coagulants) salts and water:

• Alum — aluminum sulfate
• Sodium aluminate
• Ferric sulfate
• Ferrous sulfate
• Ferric chloride
• Polymers

FLOCCULATION:Flocculation follows coagulation in the conventional water treatment process. Flocculation is the physical process of slowly mixing the coagulated water to increase the probability of particle collision. Through experience, we see that effective mixing reduces the required amount of chemicals and greatly improves the sedimentation process, which results in longer filter runs and higher quality finished water. The goal of flocculation is to form a uniform, feather-like material similar to snowflakes — a dense, tenacious floc that entraps the fine, suspended, and colloidal particles and carries them down rapidly in the settling basin. To increase the speed of floc formation and the strength and weight of the floc, polymers are often added.

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The theoretical atmospheric pressure at sea level (14.7 psi) will support a column of water 34 feet high:

14.7 psi x 2.31 ft/psi = 33.957 ft, or 34 ft

At an elevation of 1 mile above sea level, where the atmospheric pressure is 12 psi, the column of water would be only 28 feet high: 12 psi x 2.31 ft/psi = 27.72 ft, or 28 ft

If a tube is placed in a body of water at sea level (e.g., a glass, a bucket, a water storage reservoir, lake, pool), water will rise in the tube to the same height as the water outside the tube. The atmospheric pressure of 14.7 psi will push down equally on the water surface inside and outside the tube. However, if the top of the tube is tightly capped and all of the air is removed from the sealed tube above the water surface, forming a perfect vacuum , the pressure on the water surface inside the tube will be 0 psi. The atmospheric pressure of 14.7 psi on the outside of the tube will push the water up into the tube until the weight of the water exerts the same 14.7 psi pressure at a point in the tube even with the water surface outside the tube. The water will rise 14.7 psi x 2.31 ft/psi = 34 feet. In practice, it is impossible to create a perfect vacuum, so the water will rise somewhat less than 34 feet; the distance it rises depends on the amount of vacuum created.

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The trickling filter process (see Figure Below) is one of the oldest forms of dependable biological treatment for wastewater. By its very nature, the trickling filter has advantages over other unit processes. For example, it is a very economical and dependable process for treatment of wastewater prior to discharge. Capable of withstanding periodic shock loading, process energy demands are low because aeration is a natural process. 

the trickling filter operation involves spraying wastewater over a solid media such as rock, plastic, or redwood slats (or laths).As the wastewater trickles over the surface of the media, a growth of microorganisms (bacteria,protozoa, fungi, algae, helminthes or worms, and larvae) develops. This growth is visible as a shiny slime very similar to the slime found on rocks in a stream. As wastewater passes over this slime,the slime adsorbs the organic (food) matter.This organic matter is used for food by the microorganisms.At the same time, air moving through the open spaces in the filter transfers oxygen to the wastewater. This oxygen is then transferred to the slime to keep the outer layer aerobic. As the microorganisms use the food and oxygen, they produce more organisms, carbon dioxide, sulfates,nitrates, and other stable byproducts; these materials are then discarded from the slime back into the wastewater flow and are carried out of the filter. various process calculations,

Problem
A trickling filter that is 80 ft in diameter treats a primary effluent flow of 550,000 gpd. If the recirculated flow to the clarifier is 0.2 MGD, what is the hydraulic loading on the trickling filter?
Solution

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