Wastewater Treatment

Municipal Systems … ~75% of Canadians are on these waste water systems Waste leaves your home  enters a service line  enters sewer main  downhill  hits a low point and is pumped up  flows to a central station and treated

The Two Types of Sewers Sanitary Waste water from houses, businesses Sent to treatment facility Storm Rain, snow melt, runoff Usually untreated and released directly to environment

Storm water is often combined with sanitary sewage and overflow is released directly to environment

Sewage Treatment Stage 1  Pretreatment: screening out large debris

Stage 2 1) Primary Treatment  heavy organic solids, sand, gravel settle to bottom of tanks, scum and grease is released

Primary effluent may be released directly to the environment or

Secondary Treatment  “Activated sludge treament”  Anerobic and areobic bacterial digestion of sludge  Effluent is released or

Tertiary Treatment Physcial, chemical and/or biological process Removes suspended or dissolved pollutants, heavy metals, organic chemicals and nutrients (P, N) Remaining sludge is transferred to landfill, incinerated, composted or used as fertilizer

Also… Most waste water in Canada also undergoes a disinfectant process to remove disease- causing micro-organisms Usually use chlorine or Ultra Violet radiation Water that is released after this is cleaner than the natural water it enters

New types of sewage treatment Bioremediation  uses live organisms (bacteria, fungi, plants) Phytoremediation  plants used to improve contaminated soil or groundwater by absorbing contaminants or changing them into non-toxic forms

Phytoremediation - Advantages used to treat organic and inorganic contaminants used by creating artificial wetlands or piping effluent to wetlands easy to initiate and maintain economical (do not need $ equipment or training) low environmental impact decreased waste to landfills

Disadvantages slow affected by climate will not work on contamination below the root zone Plants may absorb toxic amounts of contaminants toxic chemicals may build up in plant tissue contaminants may move up the food chain