Presentation on theme: "Greywater – the invisible problem………….. Jay Bhagwan."— Presentation transcript:
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 – 800m 2 ). Soakaways installed at water collection points and standpipes should be sufficient to protect water resources and prevent health risks. Low / Medium density – l/ha.day (equates to densities of 10-30du/ha and plot sizes m 2 ). Soakaways must be installed at tapstands and in-home or yard connections should be connected to an on-site disposal system. Medium / High density – l/ha.day (equates to densities of 30-50du/ha and plot sizes m 2 ). 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 <150m 2 ). 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 600,000m 3 per day in South Africa (medium sized dam)
COD (g/day)SS (g/day) NH 4 (g/day) NO 3 (g/day) NO 2 (g/day) PO 4 (g/day)TDS (g/day)Fe (g/day) Total Coliform (cfu/day) Faecal Coliform (cfu/day) Minimum E E+08 Maximum E E+10 Median E E+08 Mean E E+09 St. dev E E+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
Variable This study (2005) Eriksson et al (2002) Källerfelt & Nordberg (2004) Pollution Research Group (2005) Stephens on et al (2006) pH Conductivity (mS/m) PO 4 -P COD Suspended solids Oil & Grease TKN Ammonia Nitrogen Sodium Water parameter Usual 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< >300 Total Dissolved solids, TDS (mg/l) 0 – 2000< >2000 Nitrate Nitrogen, NO 3 - N (mg/l) 0 – 10< >30 Ammonia Nitrogen, NH 4 -N (mg/l) 0 – 5--- Phosphate Phosphorous, PO 4 -P (mg/l) 0 – 2--- Boron, B (mg/l)0 - 2< – 3.0>3.0 pH6.5 – Sodium Adsorption Ratio (me/l) > <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