Domestic Septic Tanks

Phil House

Consider

Aerobic Anaerobic Biochemical oxygen demand

(BOD) Effluent Scum Sludge Sewage

Septic Tanks

Primary Treatment• Separation of liquids and solids

• Does not purify sewerage

Septic tanks depend on two kinds of bacteria

Anaerobic – living or occurring without oxygen

Aerobic - organisms & processes that require oxygen

B.O.D

Biochemical Oxygen Demand

The amount of oxygen consumed by chemical process and micro-organisms to break down organic matter in water over a five day period, measure in milligrams per litre (mg/L)

1. 10/10/10 water quality standard indicating an effluent quality of <10mg/L

Biochemical Oxygen Demand <10mg/L suspended solids and <10mg/L E.coil

cfu/100mL.this water quality is the standard required for grey water to be recycled to a

dwelling for toilet flushing and for the use in the washing machine. It may also be used

for surface and sub-surface irrigation.

2. 20/30 water quality standard indicating an effluent quality of 20mg/L Biochemical

Oxygen Demand and 10mg/L suspended solids. This water quality standard is

applicable for surface and sub-surface irrigation.

3. 20/30/10 water quality standard indicating an effluent quality of <20mg/L

Biochemical Oxygen Demand <30mg/L suspended solids and <10mg/L E.coil This

water quality standard is applicable for surface and sub-surface irrigation.

Explained next slide

biochemical oxygen demand . The amount of oxygen required

by aerobic micro-organisms

Suspended solids refers to small solid particles which remain

in suspension in water as a colloid or due to the motion of the

water. It is used as one indicator of water quality.

E. coli (Escherichia coli) is one of several types of bacteria that

normally inhabit the intestine of humans and animals

(commensal organism). Some strains of E. coli are capable of

causing disease under certain conditions when the immune

system is compromised or disease may result from an

environmental exposure.

Reln Plastic Tank