Recycling nutrients from urban to rural areas in Thailand
Nanette Levanius Schouw, D. of Environmental Sci. and Eng. Technical U. of Denmark, Denmark
Somtip Danteravanich, F. of Environmental Management, PSU.
Hans Mosbaek, D. of Environmental Sci. and Eng. Technical U. of Denmark, Denmark
Jens Christian Tjell, D. of Environmental Sci. and Eng. Technical U. of Denmark, Denmark
Jens Loenholdt, D. of Environmental Sci. and Eng. Technical U. of Denmark, Denmark
Corresponding e-mail : nls@imt.dtu.dk
Presented : The 5th International Symposium on Environmental Geotechnology and Global
Sustainable Development, Belo Horizonte Minas, Gerais, Brazil, August 17-23,
2000
Key words : solid organic waste, wastewater, excreta, nutrient flow, waste characteristic, waste generation rate, recycling
The potential nutrient flow back to agriculture in waste from urban/suburban areas in southern Thailand is being identified and quantified. Three model areas serve as background for this study.
The areas are Kuan Lang and Prik in the province of Songkhla, and Muang Phattalung in the province of Phattalung. Samples of solid organic waste and grey wastewater were collected at representative sources : households, restaurants, schools, hospitals, slaughterhouses, industries and fresh food markets. All waste samples were characterised physically and chemically (N, S, P, K, Ca, Mg, Cu, Zn,Ni, Hg, Cd and Pb). Charts are set up for total flows of organic solid waste and wastewater.
It is found that nutrients in the organic solid waste usually end up at the disposal sites or is recycled as animal feed within the areas. The ratio between disposed and recycled waste is highly dependent on the local collection service system. In the areas with very low public collection service, approx. 75% solid organic waste is recycled, whereas those with high service standards only has
20% recycling. Thus a good part of the nutrients in the solid waste is lost in the existing system. The generation rate is 155-270 g wet organic solid matter/capita/day. The grey wastewater is presently discarded next to the house. This means that nutrients in the grey wastewater are mainly lost into groundwater, into open gutter systems or into nearby watercourses. The generation rate is 0.08-0.14
m3/capita/day. Water flushed toilets are installed in approx. 95% of all households, and underground septic pits are used for storing and preliminary clarification of the toilet water before discharge of the liquid fraction to the gutters or underground drainage. The solid fraction of the excreta settles in the septic pits where biological degradation takes place. The tanks are rarely emptied (5-10 years). Thus most of the nutrients in the excreta are continuously transported with the liquid phase and end up in
the underground aquifer or watercourses, and are considered a lost resource in the present system.
The possibility of recycling nutrients from each of the three waste fraction is discussed.
BACK