Are You Ready for Some Tough Jobs?

In this onsite challenge triple play, we review strategies to handle wastewater produced in three uncommon settings onsite installers may encounter

Are You Ready for Some Tough Jobs?

Sara Heger collects water samples at a Minnesota rest stop during a study of several of the roadside facilities. 

Controlling water softener-related chlorine levels in public bathrooms

Chloride levels in Minnesota surface water and groundwater resources are increasing, and maximizing efficiency of commercial water softening can reduce chloride discharge to the environment. A study was conducted to evaluate water softener settings and functionality at five Minnesota Department of Transportation rest area sites and to compare chloride levels in their septic systems. Sites included Marion Rest Area (RA), Blue Earth Westbound RA, Oakland Woods RA, Fuller Lake RA and Central Minnesota Travel Information Center.

Water treatment professionals inspected water softeners, and samples were collected to evaluate chloride levels in septic system lift stations. Additionally, water-quality tests were conducted to characterize drinking water iron, hardness and chloride levels. Water softener efficiency and chloride contributions from softeners and other major sources were estimated for each site based on water use and salt use records.

Chloride levels in the septic system lift stations were found to range from 488 to 1,730 mg/L (Figure 1), with the highest chloride levels found at sites with the lowest estimated softener efficiency. The highest wastewater chloride levels were observed in Blue Earth Westbound RA, where the water softener meter was broken and the softener was set to regenerate every few days instead of on demand. Water softeners were estimated to contribute between 77% and 92% of the chloride measured across the site septic systems, with the remaining chloride coming from human waste and drinking water chloride concentrations (Figure 1).

Brine from water softener discharge has very high chloride levels, and previous research has found that elevated chloride levels may have an inhibitory effect on microorganisms in septic tanks. The chloride levels observed across the rest area sites were high, indicating they may be impacting septic system performance and treatment. Reducing chloride discharge from softeners by increasing salt use efficiency is beneficial to septic systems.

Recommendations to maximize commercial softening efficiency include using demand-based, twin-tank softeners; periodically servicing softeners to check settings and functionality; keeping records of salt purchases and use; using iron filters in areas with high iron levels and routing discharge away from the septic system; and using results of laboratory water-quality tests to establish water softener settings. If a home or facility has a water softener, it is wise to ensure it uses as little salt as needed or to direct the softener discharge away from the septic system.

Properly handling the wastewater load at a slaughterhouse operation

Slaughterhouse wastewater is not covered under most state septic regulations, as septic system sizing is based on research of typical flows and wastewater characteristics from domestic residences.

For small slaughtering facilities a decentralized onsite option for treating its wastewater may be the most cost-effective — particularly if connection to a wastewater treatment plant is not feasible.

A septic system receiving slaughterhouse waste is considered by the U.S. Environmental Protection Agency to be a Class V injection well system. Depending on the requirements of your state, county and/or local authorities, wastewater can be treated in various ways. Keep in mind that there is no one “best” wastewater treatment system. Different processors have different needs. Finding the right wastewater treatment system for the facility will depend on a number of variables.

1. First you will need to determine what type of activities will occur at the facility:

  • Slaughtering
  • Cut and wrap
  • Value-added processing
  • Sales room
  • Worker showers and/or laundry

Each of these activities will add additional loading to the system.

2. Identify which species are being processed: hogs, sheep, goats, poultry, wild game, etc. 

3. Estimate or measure the volume of wastewater output each day and wastewater characteristics. Measure or estimate the pH, total suspended solids, biological oxygen demand and FOG levels. For existing facilities, flow measurements should always be obtained. Tables (Figure 2) show flow estimates and wastewater characteristics gathered by the Niche Meat Processor Assistance Network. It should also be determined if processing will be consistent or seasonal in nature.

Option 1: In general, if it is possible to connect to a municipal wastewater treatment plant, this is often a good option. If the facility is located within reach of these services, it will likely be worth paying the initial connection fees and monthly sewer costs rather than building and managing a small onsite wastewater treatment system. Before this decision is made, the facility should contact the local public works or municipal wastewater treatment facility to find out about connection fees and estimated monthly charges. With smaller towns or undersized wastewater treatment plants, the additional loading from a larger slaughterhouse may be a challenge.

Option 2: For smaller facilities, installing a holding tank that is pumped may be an option. The holding tank waste could be land-applied or taken to a wastewater treatment plant. This is also a good option for phased growth, where the system can start as a holding tank and then an onsite wastewater treatment system can be installed once the business is more established. The holding tank should have an alarm to indicate when it is 75% full.

Option 3: A typical/conventional septic system with only a septic tank and drainfield will not work for meat processing plants because of the high levels of BOD, TSS and FOG in the wastewater. If it is a larger facility, building an anaerobic digester, pond or lagoon system may be a good option, but for smaller facilities, a septic system with advanced treatment could be a good solution. The most likely design solution would be installation of an aerobic treatment unit after settling and oil and grease removal in septic tanks. With high-strength wastewater, flow equalization with time dosing should be considered, and flow monitoring is essential for proper management. 

Other recommendations include:

  • It is best to separate the animal processing wastewater from human domestic wastewater for bathrooms, showers and laundry. The domestic wastewater will need to meet all the local/state septic regulations, whereas the remaining wastewater will likely be governed by an industrial- or agricultural-related program.
  • Use of cleaning chemicals should be kept to a minimum. Septic systems can deal with small amounts of cleaning chemicals, but if the amount is above typical domestic usage, system performance may be impacted.
  • If animals are killed in the facility, all blood should be caught separately and used, rendered or taken to a treatment facility.
  • All solid material should be dealt with as a solid waste. Fine grates should be put on all floor and sink drains to catch any small particles and hair.
  • A commercial-size effluent filter (designed for high-strength waste) should be placed on the outlet of the last septic tank. A manhole should be located over this filter, as there will be a need for frequent maintenance and cleaning.
  • A maintenance contract should be in place with a licensed onsite professional to assure the proper operation and maintenance of the treatment system.

After treatment, the remaining item for consideration is where the dispersal will occur. Depending on the quality of the effluent, size and climate, irrigation may be an option. In some areas, a subsurface drainfield may be a better option. 

Developing a treatment plan for dog kennel and vet clinic wastewater flows

Wastewater from dog kennels and veterinary clinics is not included in most septic regulations. Septic system sizing in state and local regulations is based on research of typical flows and wastewater characteristics from domestic residences. In some jurisdictions, waste from these types of facilities may be covered under animal waste regulations or prohibited from going into a septic system.

A septic system receiving animal waste is considered a Class V system by the EPA. There are no specific EPA rules dealing with animal facilities whose wastewater goes into a septic system, although the EPA does require a Class V inventory form to be completed and mailed to appropriate agencies. State codes, along with local ordinances administered by counties, cities and townships, may have provisions regarding these facilities and must be consulted.  

In rural areas, often the only option for treating the washdown water from these facilities is through a septic system. This wastewater typically has high levels of ammonia nitrogen from urine, along with large amounts of hair and sanitizer, all of which are challenging for septic systems.

Property owners should be encouraged to consider the following options:

Option 1: All waste could go into a holding tank and either be land-applied or taken to a wastewater treatment plant.

Option 2: Use an onsite septic system to treat the wastewater. If this is being done, consider following the recommendations below.

Keep human waste from the facility separate in case there are problems related to the animal waste.

A flowmeter should be installed to determine the design flow. Flow data should be collected at representative times (trying to target busy days) and over several months. If no facility exists or an expansion is planned, estimates should be made based on maximum occupancy, cleaning schedule and gallons used per washdown, and then include a safety factor (approximately 1.5 times estimated flow). A flowmeter should be installed to verify estimates.

If existing septic tanks are in place, samples should be taken to determine the quality of the effluent. These samples should be taken from either the outlet baffle of the last septic tank or a pump tank if one exists. This effluent should be sampled for BOD, TSS and ammonia. If these levels come back high, a pretreatment unit should be designed to lower the levels to normal domestic strength levels. Typical normal levels of sewage leaving a septic tank are:

  • BOD less than 220 mg/L
  • TSS less than 65 mg/L
  • Ammonia less than 60 mg/L 

If no septic tanks exist or if it is a new facility, the wastewater characteristics must be estimated. Wastewater characteristics are hard to predict and should be sampled once the facility has been in operation for three months, and pretreatment should be designed to deal with known levels. It is critical that no hazardous waste enter any onsite septic system.

The operators of the kennel or vet clinic should try to prevent medicine from entering the septic system, and the use of cleaning chemicals should be limited, including antibacterial soaps and quaternary ammonia. Onsite septic systems can deal with a small amount of cleaning chemicals, but if the amount is above typical domestic usage, the performance of the system may be impacted.

  • All solid dog waste should be dealt with as a solid waste. This could be composted or landfilled.
  • Fine grates or screens should be put on all floor and sink drains to catch any small particles and hair.
  • Extra septic tank capacity should be installed (four times the design flow) to try to catch hair that will make its way through the system.
  • A commercial-size effluent filter (designed for high-strength waste) should be placed on the outlet of the last septic tank. A manhole or hatch should be located over this filter, as there is a high potential for maintenance at this location.
  • If pressure distribution is used to distribute wastewater, 1/4-inch orifices should be designed with a minimum of 5 feet of head.
  • Clean-outs should be provided at the ends of gravity and pressure distribution lines in the event that hair does make it out to the distribution system. The lines should be evaluated at least once per year. Also, in the soil treatment area, inspection pipes should be finished above the ground surface and should be observed annually (at a minimum) for ponding.
  • Provide space for a future ATU and additional soil treatment area.
  • Recommend that the system be used under an operating permit.
  • A maintenance contract should be in place with a licensed onsite professional to assure the proper operation and maintenance of the treatment system. 



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