Preliminary treatability test of a non-conventional industrial wastewater in the wood sector: cod and formalin reduction

Abstract

Industrial activities commonly discharge a broad range of synthetic compounds directly into
water recipients without previous treatment. Despite the existence of available technologies
for industrial wastewater treatment, better understanding of treatment processes is still
required, since these waters are relatively complex and usually contain either persistent or
recalcitrant compounds. Treatment systems with low costs of implementation, operation and
maintenance as well as energy and labor saving processes ought to be developed. Biological
treatment systems are potentially good options to meet these requirements. In this study, a
preliminary investigation in lab scale was carried out with a Sequencing Batch Reactor -SBR
used to treat a non-conventional industrial wastewater generated by a wood-floor industry,
located in Nybro, Sweden. The study focused on: (i) formalin reduction in aqueous phase and;
(ii) COD reduction. The proposed SBR reached a high efficiency in reducing formalin within
the aqueous phase (from 53% to 98%) suggesting the use of formalin by the microorganisms
as a primary carbon source. On the other hand, COD reduction (-34% to 73%) was not
satisfactory, which is probably related with the presence of polymeric compounds with high
molecular weight in the urea-formaldehyde resin, Recommendations for the system
improvement are: (i) effluent recirculation; (ii) longer filling periods during each batch and;
(iii) both primary and secondary settling/ sedimentation. As a result of very high initial COD
contents (ranging between 736-5608 mg L·\ even though a high percentage of reduction is
achieved, the final effluent would still not meet the threshold limits for effluent discharges in
water bodies. Additional treatment options could be advanced oxidative processes such as
ozonation and Fenton.