DeOdor Solutions

Another “Environmentally Responsible Solution” from Key Solutions, Inc.

A new approach to odor control for confined spaces and lift stations, the patented*DeOdor Solution stops odor at the source with minimal chemical addition – a cup of fertilizer and a few pounds of scrap iron each month – by treating the nuisance odors at the source, before they leave the headspace and annoy the neighbors.

* US Patent 6,245,553

System Descriptions

DOS 75

A 300 gallon tank with three venturis driven by a 5 hp submersible pump, designed to move nominally 75 scfm of gas through the liquid in the scrubber unit. Suitable for large stations or for smaller stations with very large float differentials or open channel access. "Large" is defined as nominally greater than 200 sq.ft. of surface area or any station with less than 10 ft. of headspace depth.

DOS 25

A 140 gallon tank with one venturi driven by a 2 hp submersible pump, designed to move nominally 25 scfm of gas through the liquid in the scrubber unit. Suitable for small stations where small is defined as less than 200 sq.ft. of surface area or most station with more than 30 ft. of headspace depth.

DOS 25/75 Extra Duty Packages

This added system includes a chemical addition system and/or a second stage treatment for use where very high sulfur loadings, high dissolved solids make-up water, low oxygen content in the headspace gases, or other operating constraints require that the iron catalyst or oxidizing agent be in greater concentration than can be provided by the "scrap iron" added on a monthly basis. The high alloy pump and motor are required (and included) in these systems. Suitable for large stations or for smaller stations with very large float differentials or open channel access. "Large" is defined as nominally greater than 200 sq.ft. of surface area or any station with less than 10 ft. of headspace depth. Pricing available on a site specific basis, added to base price above.

High Alloy Pump and Motor Packages

Where the make-up water supply contains high chlorides or when the unit will routinely see hydrogen sulfide levels in excess of 250 ppm, higher alloy motors and pumps can be supplied. Standard materials of construction for the pump and motor are 304, 429, and 431 Stainless steel; High alloy systems are all 316 and 316L. Tank, fittings, flanges, nuts, and bolts are 316 and 316L in all units. Specific pricing available upon request, but typically $1,000 - 2,500 above the base unit pricing.

How it Works

An internal recirculation pump generates a vacuum when pushed through the venturi, pulling gases into the scrubber from a point just above water level in the lift station. The venturi mixes the gases with recirculating liquid in the unit's tank to remove hydrogen sulfide and other odorous materials. Leftover gases are returned from the unit to lift station headspace just below the "ceiling".

Liquid in the scrubber unit has both biology and a small amount of iron that catalytically convert and oxidize hydrogen sulfide into elemental sulfur using the oxygen from air in the headspace gases. Other odorous gases such as ammonia, organic amines, and mercaptans (organic sulfides) react with the iron, the low pH, or the biology present and are converted into non-odorous compounds.

Because the recirculating water is hotter than the ambient air temperature in the lift station headspace, the gases returned to the headspace are warm and saturated with water vapor. The circulation pattern in the headspace establishes a gradient from warm, treated gases returned near the ceiling to the suction close to the source of the odor, just above the water level in the station. This circulation pattern keeps the odorous headspace gases away from the access doors and close to its source. As the returning water vapor cools in the headspace, a mist or fog of distilled water is formed which further removes the odorous gases, dragging them down to the suction line to be treated.

Some water is evaporated from the scrubber [by design] and must be replaced continuously; this is one of the reasons for the water supply connection. The other reason - in order to prevent accumulation of dissolved solids and scale formation and to remove the elemental sulfur formed, a slight excess water flow is provided, flushing the tank once every 5-10 days without flushing out the biology faster than it can grow.

On a regular monthly basis, a balanced fertilizer is added to make certain that the biology has all the nutrients it needs to grow and prosper. In extreme cases of high food odor and low hydrogen sulfide concentrations, it may be required to add the fertilizer in smaller portions each week or every other week, but we have not encountered conditions yet where this has been necessary.

Several small pieces of scrap rebar or other iron source are suspended in the liquid to make certain that the treatment system has an excess of iron available that the biology and water chemistry need to work. When the rebar is “gone”, another small piece will be needed to replace it, but each piece should last 3-12 months or longer. Small pieces with lots of surface area are better than a single large “chunk”, but not so small as to get into the pump suction. The biology and the recirculating water will take what it needs from the iron scrap as it needs it.

The heat from the submersible pump used keeps the recirculating liquid warm (hot in the summer, many times approaching 120-140°F). The biology controls its own environment and operates at about pH 2-6, depending upon load, water supply quality, and ambient humidity. Use common sense and don’t take a bath in it.

If for some reason the entire tank is drained and cleaned out to the last drop, the biology can be started again "in a hurry" by adding 5 gallons or so of activated sludge which has been screened to remove trash and sand and lint; directions to screen sludge are available. The starter sludge MUST be screened to prevent pump clogging and wear. It is unlikely that you will ever need to replace the starting sludge, however, since the treatment system is intentionally not sterile. Adding more sludge does not make it “go faster” or “work better”. The starting sludge probably only contains a couple dozen bacteria that are the ones which do the “work” required out of the billions per liter in the sludge added. With hydrogen sulfide and odorous gases as the only food available in the scrubber, the biology that can use it are the only ones to grow, multiply, and survive. Different cities, different odor sources, different temperatures would lead to different survivors doing the work. Basically, if it isn’t washed out, cleaned entirely, and sterilized, it does not need fixing!

Where it doesn't work

 

When there are multiple vents for the headspace.

The cure is simple - close the extra vents. The process works by treating the odors in the headspace. Regardless of the arrangement, having vents to the headspace allows some untreated volume of gas to escape. When there are multiple vents, the problem is made worse because the prevailing breeze or even the slightest of temperature changes in the headspace causes drafting of the headspace gases out of the confined space and into the open atmosphere, untreated or partially treated. Rigorous gastight seals are not required - just common sense. Many times, just closing off multiple vents of a wet well are sufficient to eliminate an odor problem without any equipment required. If sulfide levels are relatively low or if suitable materials of construction have been used, corrosion will not be a significant issue.

When the headspace above the maximum liquid level is small relative to the volume displaced by the piston effect of rising and falling liquid levels.

If the volume displacement by the piston effect is smaller than the unit's capacity per minute, and of the same order of magnitude as the volume of the headspace above the maximum liquid level, there will likely not be a problem but the arrangements and installation will require close attention to detail. If the piston effect volume is larger than the unit's capacity, the piston effect will need to be diminished in order for the unit to work well. This can be most easily done by use of VFD for the pump(s) or can sometimes be achieved by lowering both the max and minimum liquid levels in the lift station so as to decrease the fraction of the piston effect - caution here to watch the net positive suction requirement of the system when changing the float levels. Where VFD's cannot be used or changing liquid level range is not feasible, the standard DeOdor Solution installation may not be appropriate.

When the headspace gas has less oxygen than the level of hydrogen sulfide.

This is a rare occasion, but possible. Slight modification of the standard unit can be made to overcome this condition upon special request. The key issue is that a mole of oxygen is required to oxidize two moles of hydrogen sulfide. With a slight excess of oxygen the system is ready at all times to handle the peak concentrations of hydrogen sulfide that pass through.
When the headspace volume varies significantly more than the volume capacity of the system AND there are multiple openings into the headspace.
This is a relatively common occurrence in large lift stations which operate on floats or liquid level sensors without VFD control of the pump(s). In particular, large lift stations with open channel flow into the "side" of the headspace suffer a piston action with each rise and fall of the liquid level. If there is not sufficient depth between the water level and the side opening, the system cannot reduce the odor level enough to avoid allowing odor to escape through the side opening. Covering the open channel helps, using a larger unit helps as well, but both of these "fixes" have their limitations; a way to truly correct the problem of an open channel entrance into the wet well other than closing the channel is the combination of minimizing the opening and using VFD controls to maintain a relatively constant liquid level, avoiding the piston action.

Installation Instructions

"Experience is a wonderful thing; it teaches you when you’re about to make a mistake the second time!" [Ellis O. Barnes] If in doubt, ask us - we've done this before!

Grounding Requirements

If the unit and electrical equipment are not properly grounded to true ground, the pump and motor will experience serious galvanic corrosion and failure. Check it twice to start with and at least quarterly or annually afterwards. Do not assume that the unit is grounded just because it's sitting on the ground.

Water supply

Without a continuous water supply and continuous overflow to "drain", the system concentrates the dissolved solids from the water into a corrosive salt cake which aggressively attacks even the 316SS construction of the unit. Arrange the water supply to the unit such that it takes intentional action with tools required to turn off the water supply.

Nuts & Bolts

The unit is constructed of 316 and 316L Stainless Steel and the venturi of carbon filled PVDF. The system functions because it slowly dissolves iron into the water in the tank, corroding the added pieces of iron intentionally. Do not use steel or 304 stainless substitute parts - they will disappear much faster than you might otherwise think.

Plumbing

Vapor line plumbing, both suction and return, are normally done in PVC. The only glue requirements are for stability, not for handling pressure. "Murphy's Law" dictates that if you make the vapor system permanent, you will need to move it, either temporarily or otherwise.

The real secret to properly installing DeOdor Solution!

The fewer possible openings in the wet well or lift station headspace and the tighter the seals and gaskets, the better the system will perform. The suction line should be as close to the liquid surface as practical yet avoid being in the water under any conditions except "emergency" high levels or when other equipment has malfunctioned. The vapor return should be as far away as practical from the suction and as high as possible inside the headspace. The larger the vertical distance between the two, the better the performance.

 

Operation and Maintenance Requirements

The heat from the submersible pump used keeps the recirculating liquid hot, many times approaching 120-140°F. The biology controls its own environment and operates at about pH 2-6. Use common sense and don’t take a bath in it.

Daily ToDos:

Make certain it’s running; it doesn’t work when it’s not. Oddly enough, this is the single largest operating problem.

Make certain the water supply is left on all the time. The system uses 30-75 gallons per day in the low humidity weather, a little less in high humidities. No daily adjustments required! The system must have overflow ALL of the time, even though at very low rates - 10 - 40 gallons per day.

Report any substantial pressure changes or any new “noises” to maintenance supervision.

Weekly ToDos:

It is a good idea to keep a weekly record of the pump pressure and temperature. Seasonal variations will cause the operating temperature to vary by 5-10°F.

Open the inspection port in the suction line just in front of the venturis to be certain that there has not been trash or other debris drawn into the line which might plug flow through the venturis. If found plugged frequently, confirm that the height of the suction line is above the "normal" high water level and that the vacuum relief hole in the suction line is open.

Monthly ToDos:

Confirm overflow rate of make-up water by visually inspecting drain line output. The rate should be at least ½ - 1½ gallons per hour, not more, not less, for either unit.

Turn off unit and inspect pressure gauge to make certain it goes to zero.

Each month add about one cup of “Miracle Grow” or equivalent potted plant fertilizer through the access port. Where sulfide levels or food odors are exceptionally high, especially if the unit's performance tapers off during the month, it may be advisable to add the half of the fertilizer in the middle of the month and half at the beginning of the month.

Check hanging piece of rebar or scrap iron, replace if missing. If in doubt, add an extra piece.

Don’t forget to turn unit back on!

Quarterly ToDos:

Check the amperage draw on each leg of the power supply to the unit. Compared to the initial reading after the unit is at operating temperature, there should be less than 5% change. If higher, or lower, remove and inspect pump, motor, and all electrical connections.

Annual ToDos:

Remove pump unit and inspect suction screen for any obstructions. Clean as required. Return to service.

 

Troubleshooting Notes

The heat from the submersible pump used keeps the recirculating liquid hot, many times approaching 120-140°F. The biology controls its own environment and operates at about pH 2-6. Use common sense and don’t take a bath in it.

If the pump discharge pressure is low:

Open the access cover while the unit is running and confirm that the water level is at the overflow AND overflowing – adjust the water flow if not.

Shut down the unit and pull and inspect the pump suction screen and the pump itself.

If it’s noisy:

Open suction union to inspect venturi entrance for obstruction. This is the typical source of noise from the system. If the opening is unobstructed, shut down the unit, pull the motor assembly, and inspect the pump suction screen. If there are no visible obstructions, call for details on how to inspect and verify pump integrity. Save yourself some work, call before you take it all apart!

 

List of Installations

  
DOS 25DOS 50 & DOS 75
SAV 21SAV 23
SAV 38SAV 64
SAV 54 
SAV 63 
SAV 65 
SAV 75 
SAV 131 

SAV 64 – DOS 50-1

Wet well:20 ft diameter, 40 ft to Top of Water (ToW)
Flow:10 mgd ADF
Pumps:Three 200 hp Flygt w/ VFD control
Location:Intersection of Bee Rd. & Skidaway Rd.
Date of Service:6/99
Other:Influent through dry pit open channel with Channel Monster screen

DOS in back cornerWet well at Station 64DOS unit at Station 64DOS at Station 64

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SAV 21 – DOS 25-2

Wet well:6 ft diameter, 18 ft to ToW
Flow:0.030 mgd ADF
Pumps:Two 10 hp Flygt w/ level control
Location:River Street
Date of Service:10/99
Other:High profile between City parking lot, City Park, and sidewalk

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SAV 65 – DOS 25-3

Wet well:20x20 ft with partial partition, 16 ft to ToW
Flow:10 mgd ADF
Pumps:Three 150 hp Flygt (?) w/ VFD control
Location:Bacon Park Golf Course
Date of Service:1/00
Other:Adjacent dry pit open channel with Channel Monster screen

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SAV 131 – DOS 75-4

Wet well:20x20 ft with no partition, 18 ft to ToW
Flow:15 mgd ADF
Pumps:Three 150 hp Flygt w/ VFD control
Location:Island Expressway at Battery Point
Date of Service:1/00
Other:Replaced failing carbon/ozone system

After attempting to use a 25 scfm unit, this site was upgraded to a DOS-75 unit with a second stage scrubber as shown below.

Station 131 with large second stage scrubber

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SAV 63 – DOS 25-5

Wet well:8 ft diameter, 20 ft to ToW
Flow:0.015 mgd ADF
Pumps:Two 10 hp Flygt w/ VFD control
Location:
Date of Service:2/00
Other:Adjacent to daycare facility

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SAV 38 – DOS 25-6

Wet well:8x8 ft , 20 ft to ToW
Flow:0.15 mgd ADF
Pumps:Two 20 hp Flygt w/ VFD control
Location:Wilmington Island
Date of Service:2/00
Other:Old wet well provided with DOS suction. Adjacent to playground.

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SAV 75 – DOS 25-7

Wet well:10 ft diameter, 25 ft to ToW
Flow:0.015 mgd ADF
Pumps:Two 10 hp Flygt (?) w/ VFD control
Location:Industry Ave.
Date of Service:2/00
Other:Industrial influent; adjacent to several small parking lots

click on pictures for a sharper image
Station 75DOS at Staion 75

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SAV 23 – DOS 25-8

Wet well:20x30 ft, 24 ft to ToW
Flow:15 mgd ADF
Pumps:Four 150 hp Flygt w/ VFD control
Location:Behind SCAD dorms with entrance off Louisville Rd.
Date of Service:2/00
Other:Adjacent to student housing

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SAV 54 – DOS 25-9

Wet well:8 ft diameter, 25 ft to ToW
Flow:0.015 mgd ADF
Pumps:Two 10 hp Flygt w/ VFD control
Location:End of Vassar St. at Railroad Tracks
Date of Service:3/00
Other:Between to residences at end of street.

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