Greywater – the invisible problem…………..

Jay Bhagwan

THIS IS NOT THE CASE IN LOW INCOME AND INFORMAL AREAS!!!

“Our guides told us that the residents of Kanana use this trench as a dumping area for household rubbish – mostly human urine and faeces. One of the guides had just finished working for a group that was cleaning the trench. While they were cleaning people disposed of their urine and faeces chamber in the trench. Some disposed 25 litre buckets and rubbish bags full of faeces…”

Focus is on taps and toilets Legislation limiting

Case of South Africa, sanitation covers grey water

Institutional fragmentation Fragmentation of

responsibilities between Water Services and Roads & Drainage

Ignorance from both community and authority OR Neglect (VALUE)

Resource or waste? Guidelines exists but

ignored

Low density – <500l/ha.day (generally equates to densities of <10 du/ha and plot sizes >800m2). Soakaways installed at water collection points and standpipes should be sufficient to protect water resources and prevent health risks.

Low / Medium density – 500-1500l/ha.day (equates to densities of 10-30du/ha and plot sizes 800-300m2). Soakaways must be installed at tapstands and in-home or yard connections should be connected to an on-site disposal system.

Medium / High density – 1500-2500l/ha.day (equates to densities of 30-50du/ha and plot sizes 300-150m2). If yard connections are supplied as recommended by DWAF, on-site disposal systems should be installed; otherwise formal washing areas with disposal options are required.

High density – >2500l/ha.day (equates to densities of >50du/ha and plot sizes <150m2). There should be off-site disposal of all effluent.

there is no ponding of the greywater (Health)

that the greywater does not get into surface water systems (environmental)

that greywater is not allowed to build up in the soil to such an extent that it becomes a hazard. (salinity)

Return flows in low income areas between 80 to 90%

estimated at just over 600,000m3 per day in South Africa (medium sized dam)

COD (g/day) SS (g/day)

NH4

(g/day)NO3

(g/day)NO2

(g/day) PO4 (g/day) TDS (g/day) Fe (g/day)Total Coliform (cfu/day)

Faecal Coliform (cfu/day)

Minimum 141.86 37.66 0.27 0.24 14.98 0.04 62.97 0.00 9.59E+09 1.28E+08

Maximum 208.00 170.21 3.78 1.27 87.23 2.55 181.18 0.09 1.88E+10 4.25E+10

Median 185.26 69.77 1.48 0.30 35.14 0.25 162.50 0.05 1.42E+10 1.72E+08

Mean 184.16 79.71 1.66 0.45 43.56 0.60 141.45 0.05 1.42E+10 1.52E+09

St. dev 23.35 46.36 1.42 0.40 29.68 0.96 45.39 0.03 6.52E+09 2.36E+09

Summary of monitored grey water loads from 7 households for 1 week

QUALITY IS 10 TO 20 FOLD HIGHER THAN WHAT IS RECORDED FOR DEVELOPED AREAS

VariableThis study (2005)

Eriksson et al

(2002)

Källerfelt &

Nordberg (2004)

Pollution Research

Group (2005)

Stephenson et al (2006)

pH 3.3-10.9 5.0-8.7 6.1-7.0 5.8-6.3 -

Conductivity (mS/m) 28-1763 32-2000 83-132 144-148 -

PO4-P 0.7-769 0.6-68 14.8-56.2 11 0.3-18.9

COD 32-11451

13-549 530-3520 1135 999-1625

Suspended solids - 6.4-330 69.0-1420 - 265.2-1261

Oil & Grease 8-4650 3.1-12 - - -

TKN 0.6-488.0

2.1-31.5 - 24-30 -

Ammonia Nitrogen 0.2-44.7 0.03-25.4

- 20 -

Sodium 96-1700 29-230 - - -

Water parameterUsual range in irrigation

water

Range at which restrictions on use for irrigation are imposed

None Slight to moderate Severe

Electrical conductivity, EC (mS/m) 0 – 300 <70 70 - 300 >300

Total Dissolved solids, TDS (mg/l) 0 – 2000 <450 450 - 2000 >2000

Nitrate Nitrogen, NO3-N (mg/l) 0 – 10 <5 5 - 30 >30

Ammonia Nitrogen, NH4-N (mg/l) 0 – 5 - - -

Phosphate Phosphorous, PO4-P (mg/l)

0 – 2 - - -

Boron, B (mg/l) 0 - 2 <0.7 0.7 – 3.0 >3.0

pH 6.5 – 8.4 - - -

Sodium Adsorption Ratio (me/l) 0 - 15 >2.9 1.3 - 2.9 <1.3

Water quality guidelines for agriculture (Ayers & Westcott, 1994)

The quality of greywater in non-sewered areas differs significantly to the greywater that is generated in higher-income, sewered areas in that there is a greater variation in the concentration of the various pollutants and at its most concentrated it should be considered hazardous.

There is therefore significant risk involved with the on-site disposal of greywater in non-sewered areas.

The focus has been on technology, however the social element is not quite understood.

Fragile community structures unable to shift beyond daily realities

There are many very innovative technical solutions. The question is how appropriate are these?

Greywater is a drainage issue and needs greater attention