WASTEWATER TREATMENT PLANT DESIGN
Term Paper 1
ALTERNATIVE METHOD FOR ONSITE SEWAGE DISPOSAL
March 2nd, 2012
TABLE OF CONTENTS
3.1 Soil Absorption System in a septic tank
3.2 Soil Failures
3. ALTERNATIVE METHODS FOR ONSITE TREATMENTS
AND SYSTEMS OF DISPOSALS
4.4 Alternative method for soil treatment and disposal systems
8 4.5 Alternative treatment devices
4.6 In-house alteration of wastewater
4. REGULATION OF ALTERNATIVE ONSITE SYSTEMS
6.7 Funding of existing state onsite programs
6.8 Operation and maintenance
6.9 Failing systems
6.10 Water Conservation
List of Figures
Nearly 30% of the homes in the United States of America depend on onsite wastewater treatment and disposal. This percentage remained constant for the last two decades and is also estimated to be constant in the coming future. It is estimated that up to one half of the septic tanks do not perform perfectly or may even fail even before their expected life. The risk of contamination of ground water and surface water quality increases with the failing of an onsite system. These result in degradation of water quality, health hazards, outbreak of diseases and lowered property values. Nationally septic tank leachate is the most frequently reported cause for the contamination of the ground water and consumption of contaminated ground water is responsible for over 50% of all reported outbreaks of waterborne diseases. Lack of affordable and effective onsite sewage disposal is a national issue. Less than 35% of the land in the United States of America is suitable for conventional septic tank soil absorption systems. These limitations and requirements have resulted in developing many alternatives for onsite technologies. This study discusses recent research on alternative onsite technologies.
2.1 Soil Absorption System in a Septic Tank
The soil absorption system in a septic tank is one of the most common treatment systems onsite. This soil absorption system consists of a septic tank, a water tight container which is usually large, and a field of soil absorption. It also contains a series of perforated pipes that are buried in the soil. This system performs two functions, the treatment of wastewater and the disposal. The septic tank provides biological treatment by removing large solids and greases. Further treatment followed by the final disposal is provided by the soil absorption field.
A septic tank is made up of a large container which is water tight (usually 1000gal). This container is generally buried slightly below the ground and also adjacent to the building to which it is serving. The greases and fats are collected in a layer on the upper liquid surface whereas the solids settle to the bottom of the tank. For the liquid to be discharged from the layers between the solids and the scum, an outlet is constructed in the septic tank. For approximately every three years, the solids and scum are pumped from the tank. The treatment or stabilization of contaminants in the wastewater are treated by anaerobic microorganisms. This process occurs in the absence of O2.
The soil absorption field consists of a series of pipes. These pipes are placed in trenches which are usually 2 to 3 feet wide and 2 to 4 feet deep. These pipes are perforated. The pipes are placed in Gravel and it is covered with top soil. The effluent from the septic tank first flows down to the pipes, then out of the perforations and finally is absorbed by the adjacent soil. The microorganisms in the soil below the trenches absorb and treat the organic material in the effluent. This treated water percolates into...
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