BIOLOGICAL INHIBITION OF SULFIDE TO IMPROVE POLYMER VISCOSITY INSTEAD OF FORMALDEHYDE DISINFECTANT

Sulfate-reducing bacteria (SRB) are ubiquitous in oilfield wastewater systems. The sulfur ions produced by SRB metabolism lead to viscosity loss of polymer solution during dilution and polymer solution preparation of sewage. To avoid the disadvantages of poor stability and short effective distance in using formaldehyde to sterilize and stabilize viscosity, biological competition method was adopted. Denitrifying inhibitors and functional bacteria were added. Viscosity stability of polymer solution prepared with wastewater after biological treatment were evaluated in the lab. The mechanism of viscosity stabilization was analyzed. The results of lab experiments showed that 30 days after biological treatment, the viscosity of the polymer solution prepared with wastewater was still above 34 mPa.s, and the retention rate of the viscosity was more than 80%, which was similar to that of the polymer solution after sterilization. It could be seen in the analysis of microbial community structure that biological treatment could restrain the activity of SRB and prevent the degradation of polymer by sulfur ion produced by SRB through activating denitrifying bacteria, which could compete with SRB for nutrient substrates. Biological inhibition of sulfur could completely replace bactericidal method in viscosity stabilization of polymer solution.