COMPARATIVE STUDY BETWEEN ADHERED AND SUSPENDED GROWTH REACTORS AFTER SEPTIC TANKS TREATING DOMESTIC WASTEWATER

Abstract

The removal efficiency of BOD5, COD, TSS and SSV were studied in two anaerobic reactors which received semiequaled effluent of a septic tank, one being adhered growth (R1, with bed of gravel Nº. 4) and the other dispersed growth (R3, without support material for microbial growth). This system was installed in the Student Residence at UFPB in João Pessoa-PB. The sewage came from two bathrooms that attended to a theoretical population of 4 inhabitants. Eleven samples of the effluent from the septic tank and from the reactors 1 and 3 were collected in the period between 28/02/2013 and 10/12/2013. Temperature and pH of the reactors ranged from 24.5 to 28.1 ° C and from 7.3 to 8.1, respectively, which are adequate for the anaerobic treatment of sewage. The BOD5 removal
efficiencies (32.8 and 27.1% in R1 and R3, respectively), COD (43.4 and 33.0% in R1 and R3, respectively), SST (56.2 and 48.0% in R1 and R3, respectively) and VSS (54.7 and 46.2% in R1 and R3, respectively) were high. It demonstrates a good applicability of these low-cost housing units, which are devoid of collective sewage system in the reduction of pollution load discharged in water bodies systems. Analysis of variance showed no significant difference at the level of 5% between the average of the corresponding parameters of the two reactors, suggesting that reactor that receives discharges from the attenuation peaks, there is no need of support bed, which may represent a reduction in costs involved.

Key Words: household sewage, sewage treatment, anaerobic reactor, attached growth, suspended growth.