Wastewater from Industrial Nitrocellulose Production and the Possibility of Their Biological Treatment

Biological denitrification is a widely used technology for the removal of oxidized forms of nitrogen in wastewater treatment plants, but in the case of heavily polluted industrial wastewater its application is not easy and requires a special approach. Biological denitrification has been applied to the treatment of industrial wastewater from nitrocellulose production with high concentrations of nitric and sulphuric acid and the pH value around 1.5. The design of the technology and implementation of this treatment plant was preceded by extensive research that mapped the behavior of denitrifying bacteria, their nutritional requirements and the limits of their use with respect to the efficiency of the process. The problem of the simultaneous occurrence of nitrate and sulphate in the wastewater was solved by the different requirements of denitrifying and sulphate-reducing bacteria for the redox potential of the environment, when denitrification proceeded preferentially. Long-term experiments resulted in finding optimal technological parameters for denitrification of high nitrate concentrations and the procedure for pretreatment and neutralization of acids in wastewater. On this basis, an operational wastewater treatment plant for nitrocellulose production was implemented. During operation, it was necessary to deal with the consequences of the uneven quality and quantity of the wastewater, such as the unfavorable sedimentation properties of the denitrifying sludge and the occurrence of inhibitory conditions caused by the accumulation of nitric oxide. The design and optimization of the control system was based on the responses of probes measuring pH, concentrations of oxidized forms of nitrogen, nitrate and dissolved oxygen. The finding that the optical luminescent oxygen probe is very sensitive to the presence of nitric oxide, which allows early technological intervention in the dosage of organic substrate and thus eliminates severe inhibition conditions, has contributed greatly to the stability of the operation. The production of nitrocellulose as an important product is completely dependent on the quality of its wastewater treatment and requires long-term stable operation of the entire process complex.