The biological control of malodors generated in the pulp and paper industry and anaerobic processes.

摘要

Pulp and paper mills are facing intense problems generated by anaerobic bacteria with the implementation of closed circuit water systems, and recycled fiber use. Propagation of volatile fatty acids (VFAs) and hydrogen sulfide (H2S) produced by anaerobic bacteria in the process stream has been one of the most significant problems caused by microorganisms. Temperature, pH, and redox potential have substantial influence on VFAs and H2S production and subsequent odor generation. Several possible techniques (biocides, aeration, adjustment of pH, etc.) are reported in the literature to overcome the odor problems; however, most of these methods are expensive, corrosive, toxic or not practical. This research proposes a unique strategy that applies a combination of electron acceptors (nitrate and perborate) to effectively control these malodorous compounds. Nitrate and perborate offer both economical and effective means of VFAs and H2S control. A product based on these electron acceptors was developed and named NT product.; Laboratory experiments showed that the NT product is a non-biocidal solution that prevents the formation of VFAs and H2S by modifying the metabolism of anaerobic bacteria rather than inhibiting the microorganisms producing them.; The NT product was applied on-site in different anaerobic processes. These experiments were performed in pulp and paper, wastewater treatment, compost and water refining mills. The application of low concentrations of NT product on-site yielded, in most cases, more than 80% reduction of VFAs and H2S.; Laboratory experiments were performed to assess the behavior of anaerobic bacteria treated with NT product. The laboratory studies defined and showed the modification of anaerobic metabolism due to the addition of NT product that did not permit the reduction of sulfate by sulfate reducing bacteria to form H2S responsible for malodors. The addition of the NT product did not favor the accumulation of VFAs. This research is the first study to describe this combination of perborate and nitrate in controlling VFAs and H2S anaerobic malodors. This study is the first to propose a model of anaerobic modified pathway using NT product that controls both VFAs and H2S malodors. Other than controlling malodors, the NT product protects human lives by preventing the formation of H2S gas and increases the longevity of the system by preventing hydrogen sulfide induced corrosion.