Effect of bacterial additives on the performance of septic tanks for wastewater treatment in the upper egypt rural area

Abstract EN

The experimental work was executed on 6 septic tanks represent two modified types located in villages of the Upper Egypt.

Three of them receiving waste with medium organic load, while the others receiving waste with high organic load.

Mixture of five selected, adapted, enzyme active producer, bacillus bacterial species has been used as additive to the septic tanks under investigation in order to test its ability to improve the effluent quality as well as increase the efficiency.

Regarding the septic tanks receiving the medium load, a slight improvement in the effluent wastewater quality was achieved few days after the addition of the bacteria.

At the 6th day, the effluent showed gradual increase in the percentages of removal in the examined parameters reaching the maximum values at day 30 and showed ranges for removal percentage(%) reaching : 91.3-94.4, 93-95.8, 90-91.7, 75-87, and 99.95 – 99.99 for COD, BOD5, TSS, oil & grease and total coliforms, respectively.

After 36 days a gradual decrease in percentages of removal was observed, showing higher values than that achieved in the absence of bacterial additives.

At the end of the experimental period (60 days) the effluent of the septic tanks that supported with cultured bacteria had the following characteristics : COD ; 77.2-104.8 mg O2 / l, BOD5 ; 44.1-58.7mg O2 / l ; TSS ; 52.9-70.6 mg / l, Oil & Grease ; 4.1-15 mg / l and total coliform 104-106 MPN / 100ml.

It is important to mention that at the same time, septic tanks without bacterial additives were able to show removal percentages (%) ranged as : 79.3-88.5, 80 - 85.5, 75.1- ,41.7-28,83 and 98.5 - 99.85 for COD, BOD5, TSS, oil & grease and total coliforms, respectively.

Regarding the other three septic tanks that receiving influent with high load of pollutants, again the actual improvement in the effluent quality appeared at the 6th day with maximum removal after 36 days, and may extend to 42 days, after addition of bacteria.

During this period, the removal percentages for COD, BOD5, TSS, oil & grease and total coliform were ranged as 93.8- 97.2, 94.5-97.0, 94.0-97.9; 64.0-93.8; 99.81-99.99, respectively.

Septic tanks without bacterial additives showed percentages of removal efficiency ranged as 64.7 – 87.2, 73.4 – 89.6, 56.7 86.9, 34.6 – 45, and 92.8 – 99.28–, for COD, BOD5, TSS, oil & grease and total coliforms, respectively.

Although, the removal efficiency of septic tanks with bacterial additives was higher in case of those receiving the high load of pollutants than those receiving medium load, the pollutants residual in the final effluent (after 60 days) of the first case are higher.