DEVELOPMENT OF A LAND LIMITED WASTE-WATER TREATMENT-PLANT FOR SMALL AND RURAL COMMUNITIES IN THE TROPICS

The treatment systems for strict and moderate land limited approaches were investigated. Both synthetic glucose and actual wastewater (domestic wastewater) were studied. For the strict land limited approach! a packed entrapped mixed microbial cell (PEMMC) process using cellulose triacetate as the polymer carrier was tested for synthetic wastewater. For the moderate land limited approach, a combined aquatic weed on the water surface and a bio-fixed film in the lower portion of the pond system was investigated for both the synthetic and actual wastewater. The actual domestic wastewater was examined in a single pond system with vertical Bow under the BOD5 loading rate of 135 Kg/ha/day. BOD5 and nitrogen removal efficiencies of more than 85% and 70%, respectively, were received. The glucose synthetic wastewater was examined in it single pond system with horizontal Bow at a BOD5 loading tate of 130 Kg/ha/day. BOD5 and nitrogen removal efficiencies of 92% and 60%, respectively, were received. For the strict land limited treatment approach: it was found that more than 90% and 85% of soluble COD and total COD (including effluent suspended solid), respectively, could he removed at the loading rate of 1.6 g COD/L/day. The hydraulic retention time of 3.5 hours and the influent CBD concentration of 200-250 mg/L were maintained and operated. This is comparable with the process performance of the conventional activated sludge for treating the domestic sewage under the same operational conditions. The PEMMC process also provides the advantages of maintaining a high SRT (Solid Retention Time) without external sludge recycling and a short starting period of less than 10 days. Application of the present two systems will be dependent on the land and/or energy requirement. It is appropriate to use the treatment system of combining the aquatic plant with the bio-fixed Bhn for moderately available land and in tropical areas. A strict land limited treatment system of course, requires additional energy input.