Community onsite treatment of cold strong sewage in a UASB-septic tank

Abstract This paper presents bench scale experimental results on the electrolysis of raw domestic wastewater. Studies carried out with consumable electrodes are discussed. A mathematical model of a small electrolytic sewage treatment unit for individual household application is developed. The energy consumption and cost of such a device are discussed. Electrolysis can be described as a process in which chemical reactions are induced at each electro-liquid interface by applying an external electrical energy source to a system of electrodes immersed in a liquid. This paper deals only with electrolysis where a direct current power supply is used as the energy source. The process is governed by Faraday' s two laws on electrochemistry. The fundamental process parameter is the electrical charge density, measured as coulombs per litre (c/1) of wastewater treated. There are two basic types of electrolysis depending on the choice of anode material. When the anode is made of dissolvable metallic material such as iron, stainless steel and aluminum, the metal dissolves and goes into the sewage as metallic ions and forms hydrated metallic oxides which act as flocculating agents. The amount of metal dissolved is proportional to the quantity of electrical charges supplied to the system. Results from a series of batch experiments showed that electrolysis with consumable electrodes is capable of removing significant amounts of organic pollutants. Total organic carbon (TOC) removal was found to be a function of charge density. Phosphate removal efficiency of 90 percent or higher was achieved at a relatively low charge density of 240 coulombs per litre with either iron or stainless steel anodes. A mathematical model was derived in the conceptual design of a household electrolytic treatment unit. The model incorporates variables such as decomposition voltage of the electrodes and electrical conductivity of the wastewater as well as the physical configuration of the electrolytic cell. The energy requirement of such a unit can be calculated from the model. It is suggested in this paper that an electrolytic waste treatment unit could be an alternative to the septic tank and tile bed system in areas where the latter is not applicable due to poor soil and terrain conditions.

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An improved small sewage treatment plant for biological purification of wastewater

Water Science & Technology ◽

10.2166/wst.1994.0575 ◽

1994 ◽

Vol 29 (12) ◽

pp. 23-29 ◽

Cited By ~ 3

Author(s):

G. Voigtländer ◽

E.-P. Kulle

Keyword(s):

Energy Supply ◽

Sewage Treatment ◽

Sewage Treatment Plant ◽

Treatment Plant ◽

Septic Tank ◽

Additional Energy ◽

Anaerobic Reactor ◽

Step Process ◽

Operational Costs ◽

Aerobic Reactor

The paper presents a small sewage treatment plant (package plant) operating without additional energy. Purification of sewage is achieved in a three-step process: sedimentation tank, anaerobic reactor and wastewater pond or aerobic reactor. The efficiency of the anaerobic reactor - in contrast to the efficiency of a common septic tank - is significantly increased by using fixed biomass systems. Further degradation of sewage compounds by adhering microorganisms occurs in pond or aerobic reactor. The bed for the aerobic biomass is made of a semipermeable plastic film and arranged in order to ensure simultaneous supply of oxygen. The three pilot plants are showing different results. The main aims of research i.e. lowering of operational costs, energy supply, minimizing of maintenance expenditure and cleaning work, reliability of degradation efficiency have been achieved so far for the anaerobic reactor.

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