In Ohio, 980,000 households dispose of their wastewater in septic systems. Periodic pumping of septic tanks is essential to the long-term operation of septic systems. The material pumped out of the tank is called septage. What happens to the septage after it is removed is often a mystery to the homeowner.
Septage disposal has varied across the nation and even across Ohio. With new regulations (40CFR503) adopted in 1993 by the U.S. Environmental Protection Agency, more uniform requirements for septage management are being adopted nationwide.
In Ohio, approximately 100 million gallons of septage are pumped each year. While not the largest waste disposal concern for the state, septage disposal affects people in every county. Because of the unlikelihood of sewer lines and treatment plants being constructed to serve every Ohio residence, management of septage will continue to be a concern for many years to come.
Safe, practical, and acceptable use and disposal of septage is the goal in septage management. This bulletin guides pumpers and regulatory officials in developing a local septage management program.
Septage is the liquid and solid material periodically removed from a septic tank, cesspool, or portable toilet. Septage is similar to other wastes, such as sewage sludge and swine manure (Table 1). Septage is from 96 percent to 99 percent water and low in heavy metals, nitrogen, and phosphorus.
| Table 1. Characteristics of septage, sewage sludge, and swine manure | |||
|---|---|---|---|
| Waste characteristics (mg/l) | |||
| Septage | Sewage sludge | Swine manure | |
| Total suspended solids | 15,000 | 30,000 | 12,950 |
| Volatile suspended solids | 10,000 | 23,100 | 10,000 |
| BOD5 | 7,000 | 18,500 | 3,700 |
| Total nitrogen | 700 | 750 | 613 |
| Total phosphorus | 250 | 480 | 212 |
| Grease | 8,000 | - | - |
| pH | 6 | - | - |
| Metal content mg/kg (dry basis) | |||
| Arsenic | 4 | 10 | - |
| Cadmium | 3 | 7 | 0.002 |
| Chromium | 14 | 120 | - |
| Copper | 140 | 740 | 0.11 |
| Lead | 35 | 130 | 0.007 |
| Mercury | 0.15 | 5 | - |
| Molybdenum | - | 4 | 0.002 |
| Nickel | 15 | 43 | - |
| Selenium | 2 | 5 | - |
| Zinc | 290 | 1,200 | 0.45 |
| Source: ASAE Standards. D384.1 and U.S. EPA Domestic Septage Regulatory Guidance. | |||
Specific characteristics of septage should be considered when handling, treating, and disposing of it to avoid nuisance and public health violations. Untreated septage has an offensive odor. Septage usually contains higher levels of grit and grease than sludge or livestock manure. When agitated, septage tends to foam and is difficult to dewater. Disease-causing organisms in untreated septage are also an important concern.
Materials pumped from commercial and industrial wastewater treatment systems are not considered septage. Restaurant grease traps; dump stations at campgrounds, RV parks, and marinas; or wastes from industrial facilities should not be mixed with septage.
The organic matter in septage makes it valuable as a soil conditioner. Some nutrients found in septage may be used as crop fertilizer. The nutrient content of the septage should be considered when developing an overall nutrient management plan.
To minimize the aspects of septage that are a nuisance, it is often incorporated into the soil. Lime may also be added to septage to reduce odors. Both tilling the soil and adding lime to septage may benefit crop production.
Several successful approaches use septage safely. Careful land application and incorporation into soil on a non-public access site maximizes the value of septage while minimizing the odors and the exposure of humans to disease-causing organisms.
Adjusting septage pH is another way to reduce or eliminate odors and disease-causing organisms before land application.