Can It Recover?

Drainfield rejuvenation can be an iffy process, but when properly applied, it helps homeowners and bolsters the onsite industry.

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Septic system repair and rejuvenation has become more common for many contractors since the economic downturn. Many others have been doing it for some time. More and more pretreatment products are being marketed for drainfield rejuvenation, and many excellent recovery techniques have been developed around the country. If you are considering such work, there are a number of issues to address.

The first may well be legal: Does the local code allow the type of repair needed? For example, you may be troubleshooting a ponded drainfield that could be recovered physically but is non-compliant for vertical separation. Some jurisdictions may allow portions of a system to meet an older code, while others may require all system components to be updated if any one component is updated or repaired.

The nature of the repair will drive the decision process. Control panel problems, leaking risers, broken lids, missing baffles and such are typically straightforward. Drainfield recovery is more complex than a new installation because many variables can be involved.

Many questions

A common belief is that if system clogging is biological, it can be recovered biologically. How do you know? If it is clogged, why is it clogged? Is it simply a matter of years of use? Or has its loading exceeded capacity?

If you suspect the system has been overloaded, is it flow? Waste strength? Both? What if the problem is only too much water? What if the problem is only too many suspended solids? What if the issue is short periods of heavy loading, like a 6-week season at a resort or camp?

What about construction problems? Are the tanks properly sized? Are they watertight? Is the drainfield level? Is the pump strong enough to properly dose the field? All of these issues can lead to ponding and hydraulic failure that cannot necessarily be solved only with drainfield rejuvenation products.

Some repair experts have found the most certain way to determine if clogging is biological is to sample the biomat for percentage of organic content. If the organic (volatile) percentage is high enough, a biological repair should be successful. In other words, if 60 percent of the clogging mat is biological, that is the maximum amount of capacity that could be recovered. But if successful, would that provide enough capacity for your customer?

What's the current loading?

It is also important to determine the current loading of a system. We used to be surprised at how strong residential waste can be, but not anymore. The fast-growing use of household products and pharmaceuticals has changed the nature of waste compared to 40 or even 20 years ago. It is not uncommon to have BOD5 well over 300 mg/L in residential septic tank effluent at troubled sites. COD can also be extremely high due to cleaners, sanitizers and similar products.

Restaurant systems that we once expected to generate BOD5 in the 600 to 800 mg/L range now commonly produce 1,200 to 1,800 mg/L. One recent report indicated that quaternary ammonia – commonly used in food service facilities – can have a nine-day residence time in plumbing. Degreasers are extremely effective at moving grease from plumbing, but then the grease can potentially reach the drainfield.

What's the upside?

Also, it is important for your customer to know what degree of success to expect with the recovery procedure, and what can be done if it is unsuccessful. It might be that it's best to build a new system. If pretreatment were to be selected as part of a replacement system anyway, then installing a pretreatment component that can help rejuvenate the system could be a good option, even if your confidence in recovery is not high.

Sometimes, because of its condition, a system cannot be recovered. For example, if drainfield rock is full of sand, installing aerobic treatment will not re-establish proper flow.

Drainfield rejuvenation provides great value to many septic system owners. Properly applied, it is also a benefit to our industry.



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