Análise causal das transformações cíclicas de espécies de nutrientes em séries de lagoas de estabilização.

Abstract

Monitoring data from two series of waste stabilization ponds operated at EXTRABES - UFCG, in the city of Campina Grande (7° 13' 11" south and 35° 52' 31" west, 550m above mean sea level), in the State of Paraiba, Northeast Brazil, previously described by Silva (1982) and de Oliveira (1990), were submitted to the path analysis for a causal model elaboration of the relationships among physical, chemical and biological variables involved in the removal of nutrients (nitrogen and phosphorus). The results demonstrated that shallow ponds are more effective in nutrients removal, being pH and algal biomass the main variables acting in the process. Deep ponds had a different behavior, maintaining more the nutrients and being more affected by both nutrient influent concentration and temperature.