What's a DAF? Dissolved Air Flotation. 3 distinct modes and all combinations in-between to lesser degrees. Entrapment of bubbles within a network of particles, growth of bubbles from nuclei within the floc particles, and attachment to floc during collision. Mostly, attachment is the main mode. "Whitewater", water filled with very small bubbles of air [50 µm]. The specific gravity of floc is usually very close to that of water, so when the air bubbles attach to the flocs, the agglomerates, literally, jump out of the water.

You are going to drink the water that goes over the effluent weir. That is guaranteed. No ifs, ands, buts or maybes. Guaranteed! So, do all possible to get it as clean as possible. There are several methods of separating solids from water. If you have lots of time, gravity is very effective and cheap. Size and density of solids are major preliminary considerations in the separation from water. Some stuff floats without any help, some drops to the bottom and some are so big hardly any effort removes them from the water. The DAF can remove a lot of the suspended solids when the relative loading is reasonable. The DAF, Dissolved Air Flotation Unit, as its name indication, works by using air to float solids out of the water. Reducing dissolved solids (color), is beyond the design of the DAF unit.

Keep records. Fill out Daily log sheet - keep it up to the minute! More recorded info may help solve problems.

Keep the blanket close to 50%. Less than the air curtain.

Loading is a quick, reliable indicator of the efficiency of the Plant

The jar test attempts to replicate the conditions in the DAF. Flush the pipe. Dump another. Catch a small amount of whitewater, then grab a one liter sample. Within the next 10 to 20 seconds, observe the coagulation, record the percent loading. This will be only a relative number indicating how much loading, how correct the polymer dosing, acid working, air working. Be consistent in the technique of getting a jar sample and the number will be believable. The best the jar test can tell you is an indication of which way to go. The jar test always tells how it WAS. Even as you grab a sample, the next foot of flow may be totally different (and sometimes I've seen it). Watch the Floc on the DAF!

First thing in the morning, check the Flow rate. Then the polymers, then the Loading. Check the air. Check the pH reading. Check the discharge tank. Check the effluent weir. Check the loading. Jar test often. Begin making adjustments as necessary (if necessary) in order to produce as high a quality effluent from the DAF as possible. Continue to make adjustments to keep the effluent as free from suspended solids as can be.

The DAF works with dissolved air. Without the air, some flotation will occur, but when everything is working good the air will literally make the floc jump out of the water.

The DAF unit will, if adjusted correctly, remove a high percentage of suspended solids. Adjusting the amount of chemicals, influent and air is somewhat tedious in order to find the best balance of each. The influent quality can change within minutes which upsets the balance. Batch operation can reduce this upsetting situation. The acid destabilizes the neutral charge of the large molecules to enable the long chain polymers to tie up the target molecules for the 50 micron bubbles of air to get trapped within the coagulated assembly which then floats to the surface. Once this mess is on the top of the water, it gets pushed into the Discharge tank, leaving cleaner water to go to the Anaerobic lagoon.

The key to effective coagulation and flocculation is an understanding of how individual colloids interact with each other. Coagulation is rapid mixing. Flocculation is slow mixing. Turbidity particles range from about .01 to 100 microns in size. The larger fraction is relatively easy to settle or filter. The smaller, colloidal fraction, (from .01 to 5 microns), presents the real challenge. Their settling times are intolerably slow and they easily escape filtration.
The behavior of colloids in water is strongly influenced by their electrokinetic charge. Each colloidal particle carries a like charge, which in nature is usually negative. This like charge causes adjacent particles to repel each other and prevents effective agglomeration and flocculation. As a result, charged colloids tend to remain discrete, dispersed, and in suspension.
On the other hand, if the charge is significantly reduced or eliminated, then the colloids will gather together. First forming small groups, then larger aggregates and finally into visible floc particles which settle or float rapidly and filter easily.

The polymers are long chain, high molecular weight, high charge molecules. Dry crystals, when added to water, begin to make long chains. The process should take about an hour for completion though it looks ready almost immediately.

ANION (AN-EYE-on)    A negatively charged ion in an electrolyte solution, attracted to the anode under the influence of a difference in electrical potential.

CATION (CAT-eye-on)  A positively charged ion in an electrolyte solution, attracted to the cathode under the influence of a difference in electrical potential.  Sodium ion (Na⁺) is a cation.

Mixing the polymers: Fisheyes, clumps and blobs can be avoided. Any highly hygroscopic material must be added slowly. First, get a lot of water in the tank with the agitator on. Add, slowly, the polymer in the widest part of the filling stream. Let the tank fill some between adding another Liter. Keep the lid on the container! This stuff absorbs water aggressively. It'll clump in the bucket and make big fisheyes. Keep it dry until mixing. Be adding the last Liter as the tank nears being full. Turn off the agitator, let the mix 'rest while. Stir once more till clear (well mixed). Should be ready to use in an hour or so. Keep Fresh. Old mix will dewater.

There are three types of polymers: anionic, cationic and nonionic. Usually anionic polymers are used to treat metallic precipitates and sludges. To visualize how polymers work, think of polymers as being long-chained molecules resembling a long fuzzy scarf. The molecules on the outer surface of the scarf are oriented so that more of the positively charged ends (+), or more of the negatively charged ends (-), are pointed towards the exterior. Thus, the polymer may be described as anionic, cationic, or nonionic (no net charge, but has both + and - sites). Velcro.

Polymers are viscous (syrup-like) and can be difficult to disperse in the wastewater being treated. When a polymer is spilled on a floor, the surface becomes extremely slippery and is a serious safety hazard. Ice is not as slippery.

Dry polymers are usually shipped in 50 pound bags. The shelf life of dry polymers is usually more than two years if kept completely dry. Opened bags should be kept in a container with a tight-fitting lid to keep out moisture. A 7-gallon plastic bucket is very convenient for this need.

In general, dry polymers are much less expensive to purchase than liquid polymers. However, the liquid polymers has an advantage of not being subject to the formation of lumps and fish-eyes which happen because of incomplete "wetting" of the dry polymer. These problems can generally be avoided if proper care is taken during mixing.

Fill the polymer tank until the mixer blade is submerged under the water surface.

Turn mixer on, turn water on.

Sprinkle the dry polymer into the area of maximum turbulence and wetting slow enough, but fast enough.

Fill the tank and mix for a few minutes. Cover. Ultraviolet energy will break the molecular bonds and weaken the polymer.

Turn off agitator - continuous mixing will shear polymer chains.

Mix enough for several hours of dosing. Mixed polymer can get 'old', lose effectiveness, dewater.

Daily DAF Checklist Date ________ Time ________ Operator (name) _______________ [initial changes only] DAF Air Pressure: ______ psig DAF SPN add [Time : amount/hours decanted/gallons decanted (each instance)] Meter end: Meter start: DAF recirculation pump #1 or #2 Manifold Pressure: ____ psig Auto or Manual System Volume: _____ liter/min Acid System Pump operating at FEB : ProMinent 28.6 gph : Manual (rate: stroke: ) AUTO: Milltronics level: [ACID] Shift Start: End:         Cationic Polymer : Concentration: 2400 mL/500 gal 1000 mL weighs 710 grams current mixing 4L/2000L = 1.4% Anionic Polymer : Concentration: 3600 mL/500 gal 1000 mL weighs 850 grams current mixing 4L/2000L = 1.7% Drawdown: ___ seconds/Liter @ % Manual Pump control: Auto (20 mA = _____ gpm) or Manual Flow rate: ____ (gal/min) Units on Hand ___ Drawdown: ____ seconds/Liter @ % Manual Pump control: Auto (20 mA = ____ gpm) or Manual Flow rate: _____ (gal/min) Units on Hand ___ Influent Controls: Manual: (out: gpm: ) Auto: (setpoint: actual: : )per cent open Discharge Flow GPM: Total Flow reading: [end]___________ Time: ______ [start] ___________ Time: ______ Effluent Controls: Manual only Effluent Water Temperature: __7___ ºF __12___ ºF __5___ ºF Skimmers Auto or Manual Percent Coverage: % Color: Character: Age: Appearance: Clear Colored Turbid Carrying solids time         Appearance: Tight Floc Loose Floc Polymer Overfeed Foam time         Auger Drain Operated? yes no Flowing? yes no DAF discharge pump Manual only Working? yes no Leaking? SPN Tanker Only in an extreme emergency.             Loading: Time 7 8 9 10 11 12 1 2 3 4 5 6 % loading                         gpm                         Blanket                         FEB level                         ww Screen                                                   EQ Feed Pumps #1 or #2 or Both FEB Tank level: [start]   Time:   [end]   Time:   Comments : ____________________________________________________

TRAINING

SAFETY

BE NICE manners have not gone out of style
BE NEAT when everything is in its place, hunting is eliminated.
BE SAFE leave equipment in the lowest energy state.
BE SURE eliminate ignorance

Electric motor manufacturers recommend starting a motor no more than 3 times in an hour, once every 20 minutes, 1200 seconds. Heat is the problem.

EMERGENCY PROCEDURES: Sulfuric Acid pump: electric power supplied by the circuit breaker inside the FEB control panel. Cationic and Anionic polymer pump power supplied from circuit breaker #5 in the RPA panel in the panel room.

CONTINGENCY PLANS

IDEAS FOR DISCUSSION

Replace Outside sumps with 500,000 gallon settling basin. This will provide much needed capacity, ease load on system, skim float (feathers, fat, guts), allow settling of solids, solve rain event upsets.

Large flow equalization basin.
Asphalt east of the east pad needs resloping to direct storm water. Concrete pad west side restructured to contain plant leaks ... storm ditch cleaned all around boiler house.

Repipe drains from Spray tower fan and biofilter to the inside plant drain. This will reduce load on #3 lagoon and allow treatment through DAF of carry over of feather meal.

DAF
Dissolved Air Flotation Unit. Air! The DAF Unit must be supplied by its own supply of air, not connected to the Plant air supply. The pneumatic panel needs to be about twice as large when it is rebuilt ( should be within the next six months.)

Polymers: Mannich = 30% charge. The ones we use = 80%

PVC pipe gluing. Tips I've learned: Buy highest quality materials; pipe, fittings, glue and cleaner solvent. Use copious amounts of cleaner solvent. Clean everything twice then twice more. Scrape the gluing area, use more cleaner solvent. Slop on glue, jam together, twisting at least 1/2 turn, if possible, squeeze together (very important) for at least 30 seconds, release slowly.

Teflon taping: Teflon tape will be effective if applied to male threads in the opposite direction the fitting is screwed into the female part. Rolling the tape off the dispenser 'backwards' makes it easy to keep the tape tight and lined up. With PVC fittings several wraps are more effective, remember, you're only going to tighten hand tight plus a little anyway. The tape is for sealing, not for ease of assembly.

Download a dxf file of the skimmer. Of the weir.