As our onsite systems have become complex with more treatment components, the need to regularly monitor performance has increased. Additional pretreatment components, ATUs and media filters all require increased maintenance to ensure performance.

Using more advanced treatment technologies than conventional septic tank-to-soil treatment has allowed systems to be installed in more sensitive environmental areas. Monitoring system performance in these areas is an integral part of protecting the environment and public health. Without systematic monitoring and sampling, the manufacturers, owners nor the environmental agencies know whether the system is performing to the required standard.

As service providers, you already know that many of the advanced treatment systems manufacturers require some type of training course or certification to install or work on their systems. These manufacturers have their own set of monitoring, maintenance and sampling programs. It is important these protocols are followed explicitly because not doing so usually voids any warranty of the system. 

WHAT TO TEST

What needs to be monitored and sampled and the frequency of those activities depends on manufacturers requirements, system location, the environmental or health risk involved, and permitting authority requirements. This applies to all systems where there is an interest in determining if the system is working the way it should.

A less complex example of a regular performance check is the requirement in lakeshore areas to have the septic tank drainfield system checked on a regular schedule. For my own system, the county requires an inspection every three years. The septic tank is accessed through the manhole, sludge and scum levels are measured, and if the total thickness of these layers exceeds one-third the operating depth, the tank is cleaned. The inspection also requires the service provider to inspect the drainfield area for any evidence of effluent at the surface. If surfacing is detected, the homeowner needs to work with an installer to repair or replace the system.

For other types of systems, sampling and monitoring frequency depends on what constituents need to be determined and what the reason for the requirement is. An example is restaurant systems where it is important when effluent to the soil treatment area is lower than 170 mg/L biochemical oxygen demand, 60 mg/L total suspended solids and 20 mg/L fats, oils and grease.

A sampling and observation schedule is put into place to determine whether these levels are accomplished by a series of septic tanks or additional pretreatment by an aerobic treatment unit or media filter. Following installation of the units, the sampling schedule should begin with frequent observations, then lengthening time in between until the long-term sampling and monitoring frequency are established. 

FIVE-PHASE SAMPING

An example five-phase sampling approach would be starting two weeks after system installation, or startup sampling would begin on a weekly basis. If the samples are meeting the required levels after two months, sampling would move to phase two — every other week for two months. After four passing samples, phase three would entail a sample once a month for three months. If the samples pass, a sample would be taken quarterly for a year as phase four. If every sample passes, then the long-term sampling period would go into effect as either annual or semiannual samples throughout the life of the system.

An approach like this provides data on how the system performs from startup through typical operation. It will detect operation differences during different seasons or time periods. System maintenance schedules can be adjusted depending on what the sample data show. With periods of high use or differences due to seasonal temperatures those can be identified and changes in operation can be made.

In environmentally sensitive areas or when an experimental system is installed, additional wastewater constituents such as nitrogen, phosphorus or bacteria may require monitoring. Examples are in areas where there are elevated nitrate levels in the groundwater or where freshwater estuaries on the coast need to be protected. Phosphorus would be sampled along lakeshores or river shoreline to reduce potential for seasonal algal blooms. Fecal coliform bacteria as indicators of potential pathogens would be sampled in areas of rapidly permeable soils or reduced ability to provide adequate separation distance to groundwater.

ADDED SAMPLING

Dissolved oxygen, pH and wastewater flow are additional constituents or characteristics that can be monitored and sampled, which can provide information on whether a system component is operating as intended. An example where DO is important to monitor is for an ATU. To provide oxygen to break down the organic matter in waste, the DO should be higher than 1 mg/L. A reading of less than 1 mg/L indicates a problem that should be investigated.

I have often advocated for always measuring flows, even in residential systems. It is a key component to the performance of any system. Having flow data when troubleshooting a system is essential and relatively easy to obtain with a water meter. It can confirm whether a system is hydraulically overloaded and solutions identified as to whether flow can be reduced or the system has to be enlarged. Research has shown systems operating on average at 80% or more of their design flow are likely to experience problems, so having that information can avoid problems before they arise.

Monitoring and sampling should be a part of our regular system maintenance schedules to ensure systems are operating the way they should to protect the environment and human health.