Excreta Disposal and Wastewater Treatment: A Comprehensive Guide
Excreta Disposal and Wastewater
Indicators of Civilization
The level of civilization of a community can be measured by different indicators, one of which is the quantity and quality of sewage collection systems.
Satisfactory sewage removal involves:
- An annual volume of half a ton per person.
- Treatment for transporting waste harmlessly or at least to avoid ingestion or food contamination.
- Household facilities and sewage disposal systems that meet established technical requirements.
Excreta Disposal Systems
Urban
Sewage
This system consists of impermeable pipes that flow underground from home installations.
Zigzag states at different levels prevent reflux and allow a slow, regular stream, avoiding collector failure.
The pipes dispose of waste into the sea, rivers, lakes, or treatment plants. In Chile, the collection system is unitary, collecting both sewage and rainwater.
About 85 to 90% of consumption in urban communities reaches sewage systems. Its final composition is 1% solids, and 99% liquids and gases.
Final Disposition of Sewage
Disposal systems consist of:
- Sea: 33%
- Rivers and lakes: 64%
- Treatment plants: 3%
Discharge into rivers and lakes must meet aesthetic requirements and pose no risk of disease transmission.
The system works well only if conditions for auto dilution and natural purification are met, a process that involves physical, chemical, and bacteriological aspects.
Objectives of Wastewater Treatment
- Avoid the risk of disease and epidemics caused by sewage.
- Allow clean water to irrigate thousands of hectares devoted to farming.
- Decrease infectious diseases caused by consuming vegetables irrigated with sewage.
- Obtain savings by improving the economic and social health of the population.
- Promote the tourism industry by having decontaminated channels.
- Allow people to enjoy their habitat, river estuaries, and beaches.
- Maintain plant and animal life.
- Promote Chilean products in international markets, ensuring they are free of contamination.
- Secure the quality of surface water sources used for drinking water.
Sewage Treatment
It consists of two stages:
- Primary treatment: Corresponds to the sedimentary material.
- Secondary treatment: Targets non-sedimentable material, i.e., finely divided or colloidal matter in solution.
Treatment accelerates the destruction of organic matter, including germs, and the final product can be used as fertilizer (compost).
99% of the liquid undergoes filtration and chlorination.
Septic Tank
A vault of solid material, plastered inside, with variable size depending on the number of people served.
- Sewage flows from the home through a T-shaped pipe, discharging vertically, and water exits through a T placed at the opposite end.
- Most suspended solids decant and undergo anaerobic digestion with dissolution, liquefaction, and volatilization of organic matter.
- The amount of sludge buildup is small but must be removed periodically through a suction pump.
- Methane gas accumulation is avoided by leaving room for it and providing an elimination route.
- The final disposition of the waters can be made to:
· Absorbent well system
· Drainage system
Allowing the slow and deep incorporation of liquids into the ground.
Rural Areas
Without Water Trawling
1. Black Pit Latrine About Health
It consists of two parts:
- Pit
- Stand or sanitary latrine
Hole or Well
- Features:
Excavation at a distance of 20 meters from any wheel, well, spring, or other water source, preferably downstream of these sources and no more than 12 meters from the house.
To prevent water pollution, it is preferred that the excavation finish 1.5 meters above the ground layer.
- Function:
Isolating and storing human waste.
- Dimension: Will be determined according to the terrain and the number of people served.
- Shape: Square, rectangular, or circular.
- A well casing should be placed to prevent wall collapse. It can be made of stone, brick, reeds, bamboo, etc.
- Duration or time it takes to fill: Depends on its capacity and the number of people it serves.
- The more time passes without replacement, the more effective the health protection and the lower the cost per person/year.
- Anaerobic decomposition begins the moment feces fall into the pit, leading to debulking (chemical conversion, gasification, liquefaction).
- When full, the well should be covered with a layer of lime and soil, and a new one built elsewhere.
Latrine or Sanitary Units
Allows isolation and protects the user.
Both pit latrines and sanitary units are built according to standards set by the Health Services System. They must have adequate ventilation through wooden pipes, asbestos cement, or other cost-effective materials.
Latrine with Septic Tank
- Features:
Device consisting of concrete or brick with a minimum of 1m3 and a depth of 1 meter, for a family of 6 persons.
- Function:
Feces enter and liquefy. The process is improved by adding some water.
Settleable solids undergo anaerobic bacterial digestion, decant, and the supernatant liquid flows out, connecting to a well system or a drainage system that allows its incorporation into the ground.
A cup and a sanitary latrine are built on top. Initially, it must be filled with water and emptied daily. Cleaning is required every 2 or 3 years.
Latrine with Chemical Pool
- Features:
Corrosion-resistant steel pond with a capacity of 400 to 500 liters, with a cup and stand on top.
The pond may also be a portable container of 40 to 50 liters, used in mobile homes, planes, and trains.
- Function:
Based on the action of a disinfectant dissolved in water, which liquefies solids, kills bacteria, and destroys worm eggs.
It uses 12 kg of caustic soda in 40 to 55 liters of water, a solution that remains active for 6 months.
At the end, it should be drained or emptied.
It can be connected to an absorbent or drainage hole, which reduces the amount of disinfectant, which is then placed every 2 months.