DISINFECTION OF SECONDARY EFFLUENTS BY INFILTRATION-PERCOLATION

Irrigation reuse is an adequate strategy to dispose of the effluents o f conventional wastewater treatment plants everywhere a chronic shorta ge of water resources is experienced. The most attractive usages of re claimed water are irrigation of public parks, sports fields, golf cour ses an edible crops, These uses require disinfection of wastewater so as to comply with relevant regulations. Conventional disinfection proc edures are fairly effective; but, in Mediteranean countries, low techn ology techniques, such as lagooning and infiltration-percolation, are often more reliable. The cost of drained infiltration-percolation faci lities is highly dependant on the volume of their filtrating sand bed. Therefore, relationship among hydraulic load, sand depth and disinfec tion efficiency are of great importance. A circular drained dune sand infiltration percolation filter, 1.5 m sand deep, with a surface of 56 5 m(2), was constructed in Vall-Llobrega, Catalonia, Spain. The filter was fed with activated sludge effluent using a pivot irrigation syste m equipped with low-pressure bubbles, The plant worked for two years, the hydraulic load ranging from 0.165 to 0.35 m per day of infiltratin g surface. Physico-chemical parameters, total and faecal coliforms con tents were monitored. A pivot irrigation system can be considered a ma jor technological improvement. Copyright (C) 1996 IAWQ. Published by E lsevier Science Ltd.