Being proactive on protozoa

If your pipes are clogged with protozoa, it doesn’t matter how many crew members you have. It won’t be enough to keep the sprinklers unplugged.

A superintendent who hasn’t encountered protozoa-related sprinkler head plugging can count his or her blessings.

I may have been the first to encounter the problem in 1986, when my employer wanted to pioneer the use of effluent for golf course irrigation but didn’t do a lot of research in preparation. Effluent that went to the irrigation reservoir had only secondary treatment. Three days after effluent delivery began, irrigation stopped. It didn’t slow down, it stopped. If I could have snapped my fingers and had the sprinklers cleaned within 10 minutes of operation, they would have completely plugged again.

The sprinkler filters were plugged by large amounts of a stringy material that was new to me. Fortunately, I have a background in limnology (fresh water ecology) and a friend who is a phycologist, an algae specialist. Using a microscope, we discovered that the culprit was live protozoa, the genus Epistylis.

The nightmare begins

Effluent discharged from sewage treatment plants is loaded with nutrients, the most problematic of which is phosphorous, which results in algal blooms. If the treatment is not thorough — which it may not be if it’s used locally for irrigation rather than returned to the environment — it may also contain undigested organic material. When you have water, nutrients and light, something is going to live in the water, especially algae. So algae proliferate when effluent discharges into the irrigation reservoir and remains there in the daylight. Both the organic debris and live algae cells are then a gourmet buffet for things that like to eat organic material as their energy source.

One of the objectives at a sewage treatment plant is to remove organic debris — measured as “biological oxygen demand” — from the water. To accomplish this, water is bubbled with air inside a digestion tank or drooled over large beds of rock (trickle filters), which are the large round beds that we are accustomed to seeing. An organism known as protozoa then attaches to the rocks or surfaces in the digestion tank. The job of the protozoa is to eat anything organic as the water trickles over. In the sewage treatment plant, protozoa are the good-guy superstars at cleaning water, and they are known by laymen for obvious reasons as “filter feeders.”

Many species of protozoa inhabit these trickle filters, but the most common look like a tulip when examined under a microscope. A root-like structure attaches to the rock surfaces, with a long stem resembling a tulip on the far end.

As a piece of organic debris or an algal cell floats by, the protozoa extends toward it and the “tulip” envelops it with the help of cilia (hair-like structures) that help draw the food inward. Once inside the “tulip,” the prey is digested and fuels the existence of the protozoa. If you’re ever short on entertainment, you can watch the whole ingestion process under a microscope.

There are plenty of protozoa inoculums in the water as it leaves the sewage plant. They are carried to the irrigation reservoir and then to our irrigation pipes, where they attach to the walls of the pipes and joyfully eat remaining organic debris, bacteria and algal cells as they float by. The protozoa “colonies” can become quite substantial in size, sometimes such that the high-flow velocity inside the pipes can tear wads of the material from the interior walls of the pipes.

This is when our nightmare begins, when the masses of material become trapped in the sprinkler head filters and plug the heads. During an outbreak of protozoa accumulating in the filters you will not have enough crew members to keep the heads functioning, no matter how large your staff. It is crippling.

This mainline strainer is plugged with a combination of protozoa and mollusks.

Unavoidably, we accept that using effluent means conditions always will be prime for protozoa presence in our pipes. We then ask how we pull the plug on the stuff, and once gone, how do we prevent the return of problem amounts of protozoa?

Potassium permanganate

When you wake up and find yourself crippled with protozoa, recognize that just killing the protozoa isn’t enough, because when it dies and releases from the walls of the pipes, a wave of it ends up in the sprinkler heads.

Partially vaporizing it can lessen the problem. For this purpose, you may use potassium permanganate (KMnO4). This is an industrial oxidizer, essentially swimming pool shock on steroids. When dissolved in water, the material oxidizes almost anything organic, such as protozoa, and turns it into CO2. The remaining elements become potassium and manganese fertilizer. In fact, potassium permanganate routinely is used in sewage treatment plants to reduce the biological oxygen demand of water before release.

However, potassium permanganate is extremely unpleasant to use. It arrives as a fine powder in a 5-gallon pail. When you open the pail, the dust goes everywhere and oxidizes everything it touches. Yours truly even ruined the vinyl top on a car 100 yards downwind. Obviously, you need good personal protection. Using it inside a pumphouse will put dust on everything in the building.

However, the material is effective. (A side note: If you have an important lake or water feature that is too green to tolerate, potassium permanganate is an express route to cleaning it up. That said, if you overdo the treatment, the lake will be purple for a couple days until the residual material reduces.)

Copper

Copper kills protozoa, and exposure to as little as 1 ppm of copper maintained for some hours does the trick. Copper sulfate frequently is used in golf course aquatics, although often ineffectively or inefficiently.

When you dissolve copper sulfate in water with a pH of 7.5 or above, it complexes with dissolved carbonate to form CuCO3. This precipitates from the solution and renders the copper for our purposes. Considering that this reaction happens within about 30 minutes, using straight copper sulfate in high-pH water is not fruitful. Someone came up with the idea of adding citric acid to the water at the same time as adding copper sulfate. This indeed keeps the copper in solution, but the acid adds to the cost and hassle of the treatment. Also, the acid is corrosive. One good friend of mine just replaced his pump station prematurely because the pumps and skid were severely corroded from routine citric acid use.

Killing protozoa is a perfect application for chelated copper sulfate. The chelate keeps copper in solution for a long time by preventing the precipitation with carbonate, regardless of high pH. Though chelated copper is more expensive, it is more effective and much easier to use because it’s sold as a liquid, typically in 2.5-gallon containers.

Pipe treatment

The name of the game for killing protozoa with either potassium permanganate or copper is: 1) Treat all of the piping system, 2) Expose it to the highest copper concentration intended, 3) Maintain that exposure for as long as possible.

Constantly feeding copper into the pumping stream beginning at the wet well during routine irrigation is not effective. Most of the copper is in the system for only a short time. Additionally, you have to use a lot of copper to get a meaningful exposure. Not only is that expensive, but you needlessly put a lot of copper on your turf.

A more effective and efficient approach is to treat the system when you don’t plan on using it for a few days, such as when rain is forecast. That way, once the copper solution is inside the pipes it can be kept there, allowing it do its dirty deeds to the protozoa for a long time. A little bit of copper can give you a high concentration if you keep it within the relatively small volume inside the piping system.

My favorite copper or potassium permanganate treatment is to add material directly into the wet well at the pump station. Someplace on the pump station there usually is a hose bib just downstream from the pumps, often on the exhaust manifold. I attach a garden hose to the bib and run it into the wet well so I can see the water stream. I then dump chelated copper solution into the wet well. At the same time, I dump in an amount of commercially available blue lake dye. Almost immediately I see dark blue water being returned from the hose into the wet well. This is my non-precise method of determining when I need to add more solution. It’s indicated by the water becoming less blue.

I then have crew members go to distant ends of the golf course and start running water, either through sprinklers or a lake-fill line. (If they are filling a lake, they run a sprinkler immediately upstream to watch for blue dye). When the blue dye (and copper) arrive, the crew clearly sees the blue streams flowing from the sprinklers. At that point, the mainline to that location is filled and we turn off the lake fill and/or sprinklers. The crew members then go to each clock and operate each valve until they see blue flowing from each sprinkler. At that point, all mainlines and laterals are filled with copper solution.

The higher the flow velocity the better for flushing protozoa or snails (dead or alive) from the walls of pipes.

While the sprinkler venting is taking place I am at the wet well monitoring the flow from the hose and adding copper and dye to maintain a near-constant color. I could, I suppose, rig a pump injector to do a more precise introduction of copper/dye. It even could be automated by a variety of techniques, however, being the dinosaur I am and as cheap as I am, my manual method works. Once all valves are turned off, it’s time to let the copper do its deadly job on the protozoa.

Flushing the system

When the exposure is completed it’s time to flush the piping system. If you used copper, it’s hoped that any protozoa in the pipes are now corpses. If you used potassium permanganate, it will not only be dead, but at least partially vaporized (it never gets it all). Eventually, though more likely sooner than later, the dead protozoa will break loose from the pipe walls and flow along with the water. It can be a bad day when large quantities end up in the sprinkler filters. If you are lucky enough to have remote lakes with large fill valves, you can use them to your advantage. Before you run any water through the sprinklers, open the lake-fill valves completely. The objective is to get a high enough flow velocity through the piping system to tear the dead protozoa from the pipe walls and blow them out into the lakes. You may have to do some creative mainline valve strategy to ensure that water is routed throughout all of the mains.

Maintenance treatments

I follow the above procedure when the system is infected enough that performance suffers, along with the suffering of the crew members assigned to clean filters. One treatment hits it hard but probably doesn’t completely wipe out the bad guys. In that case, it may be beneficial to retreat the system one to two weeks later to finish off the survivors. Eventually the corpses that don’t flush away will rot away. However, as we discussed above, more protozoa inoculum will constantly enter the system, quickly reestablish the population and leave you with the same problem.

Recognizing that protozoa in some amount always will be in the system, the maintenance object is to periodically kill the protozoa before the population gets large enough to create a problem. In the South, that likely will be monthly during the warm months when the organisms are most active. During the cooler months, a three-month interval may be appropriate.

When protozoa are flushed from the interior walls of your pipes they end up in sprinkler filters.

Aside from protozoa, a few other unwanted organisms in pipes haunt superintendents. Those are usually mollusks (snails or clams). Snails in particular can be at least as crippling as protozoa. Fortunately, mollusks are also sensitive to copper. In most cases, 1 ppm of copper will be lethal to mollusks, so a protozoa treatment also will cure your mollusk problem. If you find worms in your sprinkler filters, you may or may not have a public health issue. In my earlier superintendent days, we used effluent that was not sufficiently sanitized. My sprinkler repairman brought me a cup with worms to show what he had been finding in the filters. I immediately recognized them from freshman zoology as Ascaris, a human parasite. If you find worms in the filters, consult your public health department for identification. But before you do, consider the public relations problem that may follow if the worms happen to be the wrong ones.

Collateral copper effects

I’ve never witnessed copper toxicity on turf from the above treatments, but somewhere, someone will try hard to make that happen. One item is more concerning. Some species of fish, such as carp, may be killed with copper concentrations as low as 1 ppm. Though the copper you flush from the pipes into a lake will become extremely diluted, it’s a thought to keep in the back of your mind.

Effect of sulfur burners on protozoa

Agricultural endeavors (including turfgrass culture) are most successful when the soil pH is approximately 7. In some regions, particularly arid regions, soils are usually way above pH 7 and can benefit by correction. A popular method for lowering the soil pH is to lower the pH of the irrigation water you apply. Eventually, the soil chemistry (including the pH) will become a reflection of the irrigation water.

The most favored method of acidifying irrigation water today uses sulfur burners. These ingest dry sulfur pellets and convert them into sulfuric acid. However, water continuously is pumped through the burner and fed back into the reservoir, carrying the acid with it. So neither concentrated acid nor its hazards exist.

There is an interesting collateral effect from using a sulfur burner. Lakes became much cleaner and algae is greatly reduced, even when using effluent. I don’t know if anyone has fully explained this phenomenon, but it has long been observed that cleaner lakes greatly reduce protozoa problems. So if you want to lower pH for agronomic reasons, acidifying the irrigation reservoir may be the method of choice if issues of protozoa and poor reservoir water quality can also be cleaned up.

Lake aeration

In addition to a sulfur burner, perhaps the single most fruitful method for improving the water quality in a reservoir lake is the use of bubblers for water aeration. You typically use one ¾-hp air compressor to blow bubbles through four bubble emitters placed on the lake bottom. The misconception is that their purpose is to bubble oxygen into the water. In reality, effective oxygen exchange naturally happens at the water surface. However, lakes tend to develop layers of water that do not mix readily. Water at the surface layer has a high oxygen content and is relatively warm, whereas water in the lower layers is cooler and may be oxygen deprived. It is in these oxygen-deprived layers that undesirable organisms exist and negatively impact the water quality.

Bubble emitters create a column of rising water, much like a thunderstorm does in the atmosphere. The rising column brings the cool, oxygen-deprived water to the surface, where it exchanges gasses with the atmosphere. These same emitters are widely used in most sewage-treatment plants. The digestion tank of a plant I recently visited had hundreds of these emitters. Any effort that results in cleaner reservoir water will translate to fewer protozoa problems. Don’t overlook the effective and cost-efficient results of bubblers.

Chip Howard, Ph.D., CGCS, is president of Phoenix, Ariz.-based Turfscience, Inc. and is a certified professional agronomist and a certified crop advisor. Reach him at turfsci@cox.net or at www.turfscience.net.

Photos: Mike Huck and Chip Howard