William Angliss Institute
Certificate IV in Food Technology
Lesson Two
Waste Water Treatment
Solids
Plastics, Metals, sand, clay
Wood; Plant mater, cars, bodies etc.
Biodegradable Soluble material
Carbohydrates
Petroleum
Other organic compounds
Non- Biodegradable soluble material
Recalcitrant molecules
Dioxans
Heavy Metals
Anions
Treatment Process
esRead about sewage treatmet systems on the Seven Trent Web page
http://www.severn-trent.com/schools/sewage.htm
Primary Treatment
Secondary Treatment
PRODUCING INOCUOUS PRODUCTS
CO2, H2O, NO2-, SO4=
Producing smelly products
Ammonia, H2S, CH4
Eg:
Large diesel/gas engines burn mainly methane and drive generators
It si possible to make enough electricity to supply all the needs of the treatment plants and still have enough left over to sell to the grid.
If all the sewage and solid waste from a city was digested anaerobically there would be enough methane to generate all the electrical needs of the city. The burning of the methane produces CO2, which is a green house gas. But the total CO2 produced is no more than any other method of waste disposal. All organic mater ends up as CO2 wether it is digested under ground, under sea, or in an aerated tank or lagoon.
If waste were used to generate electricity we would not need to burn the fossil fuels like coal and oil that we now use. This means wed could halve the present production of CO2 from power and waste treatment.
Home Work:
Read the following hyperlink about treating wastewater:
Outline over all process of wastewater treatment
Examine the Yarra Valley Water Web Page by clicking on the hyperlink below. When finished return here by clicking on your "Back Button"
Yarra Valley Water http://www.yvw.com.au/corporate/infopubs/sewage/sewageTreatment.html
Can you describe the changes that occur during Primary, Secondary and Tertiary Treatment of sewage?
Consider the option of "direct chemical oxidation" to reduce B.O.D. by reading the next hyperlink:
The Direct Chemical Oxidation Option
Is this Secondary or tertiary?
Go to Lesson One