Clarifiers

Unplug Grease Lines

By: Mike Hoefler

This DrainKing Clog Buster works well to unplug grease lines. Inexpensive purchase and it use with a garden hose.

Winter Ops-Ice Free Scum Beaches

By: Plant Electrician/Operator

I know winter is almost over (maybe??), but I have to give a shout out to my electrician for this setup for the scum beaches on our primary clarifiers. Maybe someone has done this already but if you want to virtually eliminate ice buildup during those frigid months give it a try. 1500 watt, 120 V infrared heater.

Algae Control Using Bleach and Baffles

By: Dean Falkner - Sheboygan Wastewater

Algae control is a major issue with most of us, because it makes our finals look bad and clean-up takes time and effort.

Option #1: We piped the bleach feed to the clarifier trough..to help control algae in the trough itself. We alternate the feed to each clarifier. The process is simple, but we definately feed more bleach because of it. Note: I believe Oconomowoc WI has a system that feeds bleach through piping...to control algae in the trough and at the weirs..

Option #2: We replaced our old troughs with wall mounted units that are much easier to maintain. This might sound excessive...but the total cost of the project was $339,000 for replacing troughs for 4-90 ft square clarifiers and 4-105 foot square troughs for final clarifiers. The design has the trough sizing to meet the basic design of Stamford Baffles. The concrete structure has no interior bracing to interfere with walking/rinsing/and cleaning. The bottom was tapered...so there is a good velocity ... no dead spots encouraging algae problems.

These troughs actually increased the plant's processing capability and made cleaning troughs safer and easier.

Idea #3: We haven't tried it yet, but I think there has to be a better solution to provide even flows other than the saw-tooth weirs. We're looking at something more like a block pattern...with missing blocks. The low spots are perhaps 6 inches long and 2 inches lower than the high spots.

If anyone has tried this or something else...please call.

Algae Control Using Chlorinated Water

By: Paul Wautlet

We are currently testing a system that utilizes our chlorine contact tank influent flow to chlorinate our weirs. We pump from the CCT inlet channel and distribute the solution to the weir via PVC piping...So far it appears to be sucessful but we will continue to test other applicators. Our average chlorine residual runs approx. 6 ppm.

Algae Control Using Pumped Clarifier Water

By: City of Manitowoc WWTP

This system was originally introduced to us by Mike Humke of Environmental Resources, Inc. who had seen it in operation in St. Louis. We obtained that system informtion and adapted it to our tank.

The heart of the system is an electric power ring attaced to the center column of the clarifier. The power cord to the pump is fastened to the skimmer arm which pulls a trolley- type contact around the contact ring providing power to run the pump.

clarifier flushing sprayThe submersible pump is also on the skimmer arm, inward of the scum beach on a platform bolted to a support pole, four feet below the water line. 2" PVC pipe goes from the pump back up to the skimmer arm, then "tees" off toward both the clarifer center and the weirs.

Holes are drilled into the PVC pipe at custom angles to direct the spray wherever we want. .25" holes above the weirs and launders gets good cleaning action.

The weight of the pump is a factor, we had to add a counterweight on the opposite end of the collector to balance things out.

The pump run time is controlled by a timer, currently set for two hour long cycles/day. This frequency has been working pretty good. Although during sunny/hot summer days an occasional extra flushing cycle is needed to keep up with algae growth.

The system is designed to self drain, and it has been used during mild winter to remove algae. At the current rate of use, we've figured it'll save us 400 man hours per year. Payback time for installation cost would be about one year.

Drawings, details and photos are available upon request. We would be happy to demonstrate the unit in operation or answer any questions. Ron Clish, City of Manitowoc WWTP (920)683-4515.

Algae Control Using Weir Sweeps

By: Wisconsin Rapids Wastewater Treatment Plant

I normaly don't endorse a piece of equipment or manufacturer, but what Wisconsin Rapids did in 1997 saved 12 to 16 hours of operators time each week. What was the labor saving item? "Algae Sweeps". Up until june of 1997 Wisconsin Rapids used home made sweeps made from street brooms and bungee cords to knock down algae that built up on the weir and carry through to the uv system. Still there was 12 to 16 hours each week that operator used to hose down final weirs, scum beaches, UV tubes, and baffles. After some investigation I found a company called Ford/Hall that made a brush system that seem to fit our needs. I also found that a few other Wisconsin treatment plant were using these brushes. So in 1997 Wisconsin Rapids budgeted moneys to fit our 125 foot final clarifier with the sweeps. This has been a real time and money saver. The operator can't believe the time they wasted in the past hauling hose around and pulling uv tubes. For the original investment of just over $12,000 we have saved estimated $10,000 in one year on labor. If you are having trouble with algae call me and I will send out a video on the sweep. Good luck.

Fiberglass Replacement Cover for Drive Sprocket and Chain Guard

By: Mark Flock

The Sparta WWTP has two rectangular primary clarifiers. For several years we experienced severe corrosion and rusting problems on the underside of the metal guards which protect our clarifier drive chain and drive sprockets. The problem became so bad that huge metal flakes began to fall off this cover and get all over the drive chain and clarifier deck. It was a mess.

The idea was to take one of these deteriorating metal guards to a local fiberglass shop and have them make a mold from the old unit. They were then able to build us a replacement cover out of fiberglass which is completely rust and corrosion resistant and is also not affected by cold weather. It worked. The replacement cover fit over the drive mechanism perfectly and our rust and corrosion problems are gone. Total cost was less than $200.

Inlet Flow Baffles

By: Dean Falkner - Sheboygan Wastewater

Inlets for the final clarifier extended below the distribution well, allowing flow directly into the the clarifier with nothing to slow it down. As a result, there was a fair chance of washout at high flows.

Baffles were fabricated to redirect the flow "into itself" and reduce the inlet velocity of ML entering the final clarifier by roughtly 50%. The baffle was fabricated locally for about $1400 for 4 baffles and just bolted to cover the original ML inlets to the clarifier.

The retrofit is cheaper than getting a new, larger distributions well and can help reduce the short circuiting.

Primary Scum Bypass

By: Dean Falkner - Sheboygan Wastewater

Our primary scum system could best be described as hazardous, especially in the winter. The grease tended to coallesce, requiring operators to chop it in sub-zero weather. The scum box was difficult to pump, especially with the centrifugal scum pumps. The scum lines did block a couple times...creating a slimy slippery mess in the tunnels when the line had to be cleaned. We also used to have to add caustic and mix the "mess".

We requested permission to bypass the primary scum system from the DNR. With cautious reserve and promises to be able to reestablish the collection at the first sign of trouble, we kind-of got permission. (A reminder that the old Jones Island facility never had primary clarfiers...so even it didn't have primary scum removal.)

To achieve the change and not block the weirs, we only opened the scum ring in a few small areas. We bent the ring back to the area of the weir, so the grease was directed to small areas. We then lowered the weir in the area of the opening....so the grease flows easily from the clarifier.

Once the scum entered the aeration basin, it gets a growth of bacteria/slime that helps to prevent the grease from collescing at the final clarifiers. It flows into the scum box easier.

Our scum pump upgrade with positive displacement pumps was the last piece to the project. The scum is pumped through a WAS line to our gravity belt for thickening, prior to anaerobic digestion.

Reliable Secondary Scum Pump Upgrade

By: Dean Falkner - Sheboygan Wastewater

The centrifugal scum pumps we had created problems. It took a long time to pump and flush the scum boxes whenever we had a "fluffy scum". Also, we had operators complaining that the "other operator" just pumped the water out of scum boxes.

The suggestion we got was to replace the centrifugal scum pump with un-used progressive cavity pumps we already had. To make the system workable, we installed valving to allow us to isolate and pump any scum box alone. The normal pro-cav pump discharge end was used as the suction, with the motor reversed...giving it great suction power. To prevent the pump running dry for extended times, the pump is coupled to a timer that limits run time to about 10 minutes and added a small water line with a solenoid valve that leads to the pump suction piping...supplying a little water whenever the pump runs. We also added a reversing switch to the motor, making it possible to back-flush into the box too.

Realistically, a variety of positive displacement pumps should work to do the same thing. The timer and minimal water supply system should help make that workable. Like any "new application"...double check with a distributor/rep to confirm potential problems are addressed. Good luck!!

Scum Arm Skimmer Blade Lifting Device

By: Ron Altmann, Matt Kube

This simple device was made to raise our primary scum arm skimmer blades out of operation in cold weather preventing scum from freezing on the scum trays. Due to the light weight and rigidity of the skimmer device itself, the lifter was placed at the outer end of the skimmer for easy access from the perimeter of the clarifier. A hook on a pole is used to lift and trip the arms into position. If you look closely there is a notch in the iron that is engaged on to another a piece of iron (perpendicular to the notched iron) to hold it in the raised position. Hooking the top eye and lifting with a quick jerk drops the arm back into operating position.

Scum Arm Skimmer Lifter With Trip Device

By: Ron Altmann

Our final clarifier scum trays ice up in cold weather causing damage to the scum arms skimmer blade device or sheared clarifier drive pins. Because scum is not a problem in our finals, the skimmer blades can be lifted out of operation for weeks without much of a scum layer building up on the clarifier surface.

A day or so before cold weather is expected, an operator (situated on the clarifier catwalk) uses a pole with a hook at the end to grab a loop on the skimmer blade and lift it into the raised position. A notch catches on an angle iron that is perpendicular to the notched iron to engage it into position. To lower the skimmer blade back into service, a second device attached to the clarifier catwalk is lowered to trip the latch and the skimmer falls onto the scum beach. The position of the trip device is strategically located so that the skimmer device falls onto the scum beach preventing damage that could result if the heavy scum arm fell freely. (onto the water).

It's hard to see the construction of the unlatching device from the picture. It is made from two mirrored "L" sections spaced so the piece with the notch fits through. The "L" section is solid on the bottom and is hinged at the 90 degree corner. As the scum arm passes by the pipe (lowered from the catwalk) the top of the "L" piece hits the pipe - pushing the top part - causing the lower left end of the "L" piece to raise. This lifts the notch from the catch and lowers the skimmer arm. Though it's hard to see in the picture, a small spring returns the "L" section back to the original position.

Scum Tray Plugs

By: Ron Altmann

At Waukesha's Wastewater Treatment Plant, there is a flushing water line permanently attached to our primary clarifier scum line. It is used on each shift to flush the scum lines and to clear plugged lines. In order to flush open a plugged line, the scum tray drain lines must also be blocked.

In the past, drain kings have been used, but due to the grease in the pipes, they would pop out as soon as the water pressure built up. To more easily perform this task, plugs were modified with an attachment that goes around the scum arm guide over the scum tray. This allows the plug to be loose enough to fit freely inside the drain line, yet stay in place when water pressure is applied to clear the line. Using these plugs has cut the amount of time needed to clear a line and eliminated the need to go out on the scum tray itself to insert a plug - making it a safer operation.

NOTE: Make sure the clarifier drive is off before using these plugs or damage to the scum arm and/or skimmer blade will result! For added convenience, provide a start/stop station at the scum box.

Scum Tray Flushing Device

By: Ed Artymuik, and Roger Tarman

The photo above shows a clarifier with the water level lowered to show the device. In normal operation, only the upper portion of the lever is exposed above the water's surface.

As the scum arm comes around, it contacts the upper part of the lever, As the scum arm proceeds, it lowers the lever and raises a lid allowing water into the scum tray.This second drawing is similar to the first and is the method we used. Unfortunately, we don't have a picture available so please excuse the crude drawing. The principle of operation is the same as above. The only difference is this device uses check balls from piston pumps for the valve. As the scum arm proceeds it contacts the lever, lowering the upper portion of the lever. At the fulcrum (pivot point) the action is reversed and the lever raises the ball allowing water into the tray.

Scum Tray Warmer

By: Ron Altmann

Pictured is a prototype device that sprays flushing water underneath the scum tray's beach to warm it and prevent scum from freezing on its surface. The below to the left shows the device out of operation to view three half inch pipes (they are hard to see in the picture) that spray water up onto the bottom of the scum tray. The flushing water supply hose is attached to a 90 degree swivel connector that is normally turned 180 degrees (from what's in the picture) during operation. The picture immediately below shows the warmer positioned for operation. It worked well on one of our coldest days.

Another idea that I think will work, but haven't tried, is to enclose the area under the tray and run water into it. A small flow of water should keep the tray warm or use some type of heating element. At Waukesha, pumps continuously run providing a static pressure at all times. Thus we have a rather cheap source of flushing water (or should I say it doesn't cost much more to use more water). If your treatment facility has no source of flushing water, a submersible pump in the clarifier could provide the water.