Sewage Wastes Flashcards
What does sewage waste comprise of? (8)
Complex Addition Industrial / Human wastes Suspended Solids Pathogens Heavy metals Nutrients Endocrine disrupting systems Oxygen Demand
What are the four ways in which sewage can reach the coastal enviroment?
Coastal Outfalls
Combined sewer outflows
cruise ships
recreations vessels
What issues are caused because of sewage?
Direct environmental effects destruction of habitat aesthetic pollution risks to human health socioeconomic
Explain the effects of aesthetic pollution
The can have large effect on the tourism industry as no one wants to be swimming where there is poop, sewage debris can also be washed back inland and be caught on the swash / backwash cycle causing an issue for surfers (surfers against sewage)
What is the BOD
This is the breaking down of organic compounds by bacteria, which use dissolved oxygen in the process, thus taking oxygen out of the marine system
What occurs at the BOD increases (on a graph)
The dissolved oxygen content decreases, it is the direct opposite curve of the BOD increase.
Give an example of an Acute Pollution event and some facts
Thames 2005 - There were 125 days where DO was less that 30%. Then during 2011 there was a major release of pollutants and 3000 fish died :(
What is the impact of chronic pollution on the marine environment
If the area becomes grossly polluted the it is unsuitable for all macro fauna organisms and can only be occupied by a small number of species. It goes from= Gross Poll - Poll - Transitional - Normal
What is the effect on Coral reefs
As nutrient concentration in the reef rises then eutropfication can occur which means the % cover decreases
How much of global sewage is treated?
<10%
What are the five stages in sewage treatment works (including the pre and post stages)
- Screening
- Primary
- Secondary
- Tertiary
- UV / Chorlification
What occurs in the screening process?
This is the removal of large objects and grit, to allow the rest of the plant to function and prevent blockage
What occurs in primary treatment
Settlement tanks, removal of fine solids (some bacteria) to form sludge
What occurs in secondary treatment
Biochemical degradation, through air-rating the tanks and introducing “good bacteria” which remove viruses, dissolved organics, and nutrients phosphate and nitrogen
What happens in tertiary treatment
further settlement and removal of sludge, removal of more bacteria.
What can be the last stage in sewage treatment
UV light which kills anything living left, or that addition of chemicals such as chlorine, but these can be just as bad for the final receptor
What is sewage sludge?
semi-solid material that is left over from sewage treatment works
What was the former practice for sewage sludge disposal
Offshore dumping, UK had 15 registered sites. But in 1999 UK, 1988 US bans came into place to prevent dumping
How is sludge disposed of now?
Landfill
Incineration (for bio-gas production)
What is sludge reused nowadays?
Agriculture
forestry
land reclamation
Long vs short outflows, BOSTON example, talk through it
The new longer outfall will mean there is a % percent effluence seen closer insure, where as the current one the % seen is higher. Even in summer when its a lot worse
Give three examples of new sea outfalls with their lengths
Brighton - 2.5 km
Sussex - unknown
Newport - 2.5 km
Talk through the Lodz example
This is an example of a sustainable sewage management and treatment, the sludge is used in the formation of willow plantations, which is then converted to biofuel, and wetland construction occurs from purified sewage which then protects from storm events
What may be public concerns with regards to sewage efflence
Surfers against sewage
Health protection authority
Blue flags / tourism industry
Beach watch
