The Engineering of Septic Tank Pumping

septic tank engineering

 

A septic tank is usually made up of concrete, plastic, or fiberglass where sewage flows in to undergo primary treatment. It is an underground chamber that is used in regions that do not have sewerage systems. The treated effluent that has undergone treatment is then released to the septic drain field, subjected to further treatment. Biofilters and aerobic systems are onsite wastewater treatment units incorporated with septic tanks to induce aeration artificially. Septage accumulation rate usually supersedes the decomposition rate; thus, the fecal sludge needs to be removed after some time by a vacuum truck.

Septic tanks are usually underground chambers of concrete, plastic, or fiberglass where sewage flows in to undergo primary treatment. An inlet wastewater pipe usually drains into the septic tank, while an outlet pipe at the other end usually drains into a septic drain field. The T pipe connections generally allow the liquid to flow in and out of the system without disrupting the crust’s surface. Wastewater flows in through the inlet pipe into the septic tank, giving room for solids to settle at the bottom while the scum floats. Further settlement usually takes place in this second chamber. One needs to conduct a percolation test to ascertain the soil’s porosity is adequate to act as a seepage field before installing the septic tank.

Desludging is the process of siphoning out fecal sludge from a septic system by a vacuum truck. Several health authorities prefer tanks to be emptied at certain times while others prefer an inspector’s decision. Various systems need to be pumped after several years, whereas others persevere for up to ten to twenty years before being pumped again. Anaerobic decomposition is usually ignited when a tank becomes full. You should not empty the tank as some settled solids need to be left behind to preserve the microbial populations to continue the process of anaerobic degradation.

how the septic tank works

How the septic system works

An inlet wastewater pipe usually drains into the septic tank, while an outlet pipe at the other end usually drains into a septic drain field. The T pipe connections generally allow the liquid to flow in and out of the system without disrupting the crust’s surface. Wastewater flows in through the inlet pipe into the septic tank, giving room for solids to settle at the bottom while the scum floats. Anaerobic digestion usually acts on the settled solids reducing their volume while the liquid proceeds on to the next chamber through the dividing wall.

Further settlement usually takes place in this second chamber. The remaining relatively clear liquid drains away into the septic drain field through the outlet pipe. One needs to conduct a percolation test to ascertain the soil’s porosity is adequate to act as a seepage field before installing the septic tank.

The excess contaminated substances are destroyed in the soil. The excess water is abolished through soil percolation, evaporation, and absorption by plants’ roots and is eventually abrogated either through transpiration or accessing groundwater or surface water. A trench filled with stones then distributes the wastewater all over the seepage field through drainage holes. The volume of sewage is directly proportional to the seepage field’s size, with the drainage field’s porosity being inversely proportional to the field’s size.

The entire system can function by gravity. However, where topographic considerations require, a lift pump can be used. Several tank models need siphons or other technologies to hasten the volume and the outflow’s speed to the seepage field. This, in turn, will evenly fill the drainage pipe and increase the field’s functionality by evading premature bio clogging. A two-stage septic system in which the sludge is digested in a different chamber is known as an Imhoff tank. This prevents the combination of digested sludge with fresh sewage. A second stage is introduced in specific septic tank models; the initial stage’s effluent undergoes aeration before being released into the drain field.

An odor free septic tank is usually deemed to be an effective operating system. Apart from timely inspections and desludging, the septic tank is generally expected to last for several decades, with few repairs being done to it.

desludging a septic tank

Desludging

During desludging, the fecal sludge is usually siphoned out by a vacuum truck. The solids’ input, the indigestible solid’s amount, and the ambient temperature usually detect how often the tank needs to be emptied. System characteristics, usage, and a guideline of the relevant authority also dictate how often the tank needs to be desludging. Several health authorities prefer tanks to be emptied at certain times while others prefer an inspector’s decision. Various systems need to be pumped after several years, whereas others persevere for up to ten to twenty years before being pumped again. Anaerobic decomposition is usually ignited when a tank becomes full.

It would be best if you did not empty the tank as some settled solids need to be left behind to preserve the microbial populations to continue the process of anaerobic degradation. Also, empty tanks are usually prone to destruction by hydrostatic pressure resulting in the tank partially ‘floating’ from the ground. This is typically common during floods or too wet conditions.

Maintenance

Some of the forms of neglect that may damage the septic system include:

  • User’s behavior
  • Drainage clogging is positively contributed by cooking oils and grease being drained into the system. They are usually hard to undergo degradation, thus resulting in odor issues and difficulties during desludging. Also, Flushing of inorganic waste products such as cotton swabs, condoms, menstrual hygiene products, or cigarette butts clogs the septic tank causing it to fill faster. You are being advised not to flush such materials into the septic tank. Doing food wastes into the system tends to exhaust the system with solids making the system more susceptible to destruction.
  • Some chemicals tend to destroy the septic tank’s components and eliminate the bacteria required in the septic tank to operate optimally. Such chemicals include herbicides, pesticides, paints, solvents, and materials containing excessive bleach or caustic soda concentrations.
  • Brine discharge emanating from water softeners potentially destroys the bacteria needed for wastewater breakdown. The excess wastewater usually mixes with the brine to reduce its effect on the septic system.

Other factors

  • Trees and shrubbery usually have roots that tend to protrude on top of the tank or seepage field, blocking or rupturing this tank. Trees surrounding the septic tank pose a risk to potentially penetrate the system as time goes by, resulting in the concrete developing small leaks and cracks. Such roots usually cause adverse flow issues due to clogging of the drainage pipes. Also, trees tend to grow tremendously due to the readily available nutrients from the septic system.
  • Storage buildings and playgrounds also pose a threat to the septic system. Such structures are usually surrounded by impervious surfaces such as parking areas, which adversely affect the system’s efficiency and eventually destroy the tank and the absorption system.
  • Exhaustion of the system by excessive water flowing into the system. Floods, unprecedented melting of snow, high rainfall may disrupt the operations of a seepage field. Such conditions may cause a black flow, disrupting the tank’s normal functions. High winter water tables may also cause the groundwater to flow back into the septic tank. Eventually, biofilms will form on the pipes of the seepage resulting in blockage. Such a failure can be referred to as “biomat failure.”

Nutrients in the effluent

Environmental impacts

Odor and toxic gas emissions

Wastewater usually consists of sulfates, which, under normal anaerobic conditions, get reduced to hydrogen sulfide, a smelly and hazardous gas. Ammonia is also formed as a result of the reduction of nitrates and organic nitrogen compounds. Traces of methane gas may also be released. Fermentation usually takes place due to anaerobic conditions that end up releasing carbon (IV) oxide together with methane.

Nutrients in the effluent

A septic tank’s operations alone cannot effectively eliminate nitrogen compounds capable of causing algal blooms in waterways to which water from the septic system flows. The use of a nitrogen-reducing technology, or ensuring citation of the seepage field, is carried out effectively to eliminate any effluent risks flowing directly into water bodies. The fermentation process results in the septic tank’s contents to be rendered anaerobic with reduced redox potential. This results in the preservation of the phosphates in a soluble form. Phosphates released from the septic tank into the physical surroundings can ignite plants’ incredible growth, such as algal blooms. Such plants usually constitute blooms that potentially contain toxic cyanobacteria.

The soil usually can retain phosphorus, which is large enough to manage the wastewater via an average residential septic tank. There is typically an exception when the seepage fields are found in sandy or coarser soils in an area close to a water body. Due to the decreased particle surface area, such soils tend to be saturated with phosphate, which will then proceed past the treatment area, threatening the eutrophication of surface waters.

Groundwater pollution

In areas having enormous population densities, the threat of groundwater pollution is always increasing. To minimize residential growth that might boost the demand for an expensive centralized sewerage system, the option of constructing moratoriums and subdivision property limitations is often imposed. Keeping track of the existing septic tanks is usually helpful but only for a short time. It usually tends to become less effective as a basic remediation plan as the population density increases.

Surface water pollution

Regions close to water bodies filled with fish meant for human consumption, septics that re-inefficiently maintained increases pollution levels that can force harvest restrictions and recreational harvest closure

Points to Consider

Some of the forms of neglect that may damage the septic system include the user’s behavior. This is because drainage clogging is positively contributed by cooking oils and grease being drained into the system. They are usually hard to undergo degradation, thus resulting in odor issues and difficulties during desludging. Some chemicals also tend to destroy the septic tank’s components and may even eliminate the bacteria required in the septic tank for it to operate optimally. Brine discharge emanating from water softeners potentially destroys the bacteria needed for wastewater breakdown.

Trees surrounding the septic tank pose a risk to potentially penetrate the system as time goes by, resulting in the concrete developing small leaks and cracks. I saw a really bad split septic tank when doing septic tank pumping Eustis FL.  The tree roots had wrapped around the tank like an anaconda and the pressure made it split open. Playgrounds and storage systems are usually surrounded by impervious surfaces such as parking areas that adversely affect the system’s efficiency and eventually destroy the tank and the absorption system. To minimize residential growth that might increase the demand for an expensive centralized sewerage system, the option of constructing moratoriums and subdivision property limitations is often imposed. A septic tank’s operations alone cannot effectively eliminate nitrogen compounds capable of causing algal blooms in waterways to which water from the septic system flows.

A vacuum truck is always used to siphon out the settled solid wastes. A septic tank’s location in a community or even at home should be constructed away from water sources. Untreated wastewater usually contains harmful chemicals that end up polluting such water sources. Whenever water sources are contaminated with such toxic substances, people using the water from such sources stand a chance of contracting water-borne diseases. In areas where the population is considered high, enough considerations need to be put to ensure that the appropriate size and number of septic tanks are constructed to accommodate them.

Conclusion

Before you build a septic tank, you need to consider the location of water bodies around, the community it is going to serve, the structures and plants in the area you plan to construct the tank, and the weather conditions experienced in the area. Flood water and high winter water tables have been known to overpower the septic tank’s normal operations, causing a backflow disrupting the system’s operational capabilities. Just one wrong move when building the septic tank will not only jeopardize your health but the health of others. Technologies put in place to try and decontaminate water bodies should contamination occur is usually very expensive so we are advised to kindly preserve our water sources.