Greywater Treatment. What is greywater? Not blackwater Kitchen water is sometimes treated with blackwater due to its high solids content.

Greywater Treatment

What is greywater?

• Not blackwater

• Kitchen water is sometimes treated with blackwater due to its high solids content

What about black water?

• Don’t make it black in the first place and save yourself the trouble of dealing with it.

• And if you do, don’t mix it with the grey water, at least until after its treated.

What is in greywater that needs to be treated?

• Mainly we are dealing with: fats, oils, detergents, soaps, food, hair.

• Potentially may contain contaminants such as bacteria, protozoa, fungi and parasites.

• In general it is pretty clean though, as long as you don’t store it.

What sort of volumes are we dealing with?

• Varies hugely• From 220 litres per person per day - Luxury homes with insinkerators, high volume shower , bedays, etc• Down to 100 litres for households with

compost toilets or re-used flush water(numbers from A.R.C.)• The average per person is 180L (nth shore)

Average Household Water Use

Some more numbers to get a feel for where that water comes from

• A toilet flush is usually either 11 L/5.5 L or 6 L/3 L

• The average is 5 flushes per person per day, - 11L flush = 55litres x 4 people = 220 L/day = 80300 L / year

Washing machines• Average use between 100 & 200 Litres per

wash.

Dishwasher• 40L per load

Bath• 150 – 200L

Shower75L for every 5 minutes

Remember that water from rinsing her nappies will contain fecal matter

What are the benefits of on-site greywater treatment?

What are the drawbacks?

What are the onsite treatment options?

Septic tanks are most common.

Standard disposal field

Benefits and drawbacks of septic tanks

• Benefits• Proven technology with a wide range of suppliers • Low or no power consumption • Inexpensive • Three-yearly pump-outs only • Drawbacks• Council may be resistant, especially on smaller sections and the

system relies upon the soil for completion of treatment • Require sufficient land area and larger setbacks from ground and

surface water • Dependent on the (sustained) treatment capacity of the soil • Nutrient loss off property

Aerated septic tanks

Benefits and drawbacks of aerated septic tanks

• Benefits• Wide range of off-the-peg systems • ‘All-in-one’ packaged plants • Relatively economical to purchase • When operating well can produce a high quality effluent which

makes disposal easier. • Well accepted by council • Drawbacks• Significant power consumption, expensive operation • Can be noisy • Maintenance can be costly (replacement pumps, etc) • Cope poorly with fluctuations in input (whether up or down) so less

well suited to holiday homes, etc

Vermicomposting

Benefits and drawbacks of vermicompost system

• Benefits• Probably cope better than other systems with a garbage grinder

and even some chemical use • Produce a reasonable quality effluent • Low (or no) power consumption • Can be quite compact units • Can be used with drip irrigation (some systems) • Drawbacks• Poor nutrient reduction (nitrogen/phosphorous) (may be OK or

even a benefit if water is used appropriately in a low-sensitivity receiving environment)

• Some councils accepting of well designed systems, others are less so.

Taking Multi tasking to the next level