Sawanya Laohaprapanon

Anaerobic baffled reactor coupled with chemical precipitation for treatment and toxicity reduction of industrial wastewater

This study describes the reduction of soluble chemical oxygen demand (CODs) and the removal of dissolved organic carbon (DOC), formaldehyde (FA) and nitrogen from highly polluted wastewater generated during cleaning procedures in wood floor manufacturing using a laboratory-scale biological anaerobic baffled reactor followed by chemical precipitation using MgCl2·6H2O+Na2HPO4. By increasing the hydraulic retention time from 2.5 to 3.7 and 5 days, the reduction rates of FA, DOC and CODs of nearly 100%, 90% and 83%, respectively, were achieved. When the Mg:N:P molar ratio in the chemical treatment was changed from 1:1:1 to 1.3:1:1.3 at pH 8, the NH4+ removal rate increased from 80% to 98%. Biologically and chemically treated wastewater had no toxic effects on Vibrio fischeri and Artemia salina whereas chemically treated wastewater inhibited germination of Lactuca sativa owing to a high salt content. Regardless of the high conductivity of the treated wastewater, combined biological and chemical treatment was found to be effective for the removal of the organic load and nitrogen, and to be simple to operate and to maintain. A combined process such as that investigated could be useful for on-site treatment of low volumes of highly polluted wastewater generated by the wood floor and wood furniture industries, for which there is no suitable on-site treatment option available today.

Wastewater generated during cleaning/washing procedures in a wood-floor industry: toxicity on the microalgae Desmodesmus subspicatus

In industries based on dry processes, such as wood floor and wood furniture manufacture, wastewater is mainly generated after cleaning of surfaces, storage tanks and machinery. Owing to the small volumes, onsite treatment options and potential environmental risks posed to aquatic ecosystems due to discharge of these wastewaters are seldom investigated. In the present study, the effects of cleaning wastewater streams generated at two wood floor production lines on Desmodesmus subspicatus were investigated. The microalgae was exposed to different wastewater concentrations (100, 50, 25, 12.5 and 6.25% v:v) and the algae growth evaluation was based on in vivo chlorophyll fluorescence, cell density, cell size (number of cells/colony) and cell ratio (length/width). Inhibitory effects of the tested wastewaters on the microalgae were positively related to concentration and negatively related to exposure time. The EC50, 24 h of blade cleaning wastewater (BCW) and floor cleaning wastewater (FCW) were 3.36 and 5.87% (v:v), respectively. No negative effect on cell colony formation was caused by BCW, whereas an increase of 90% unicellular cells was observed in FCW concentrations below 50% (v:v). At the lowest concentration (3.13% v:v) where no growth inhibition was observed, both wastewater streams caused changes in cell dimensions by increasing cell length and width. To conclude, wastewaters generated during cleaning procedures in the wood floor industries can have severe environmental impacts on aquatic organisms, even after high dilution. Therefore, these wastewaters must be treated before being discharged into water bodies.

Electrocoagulation coupled to activated carbon sorption/filtration for treatment of cleaning wastewaters from wood-based industry

The objective of this investigation was to study the use of a coupled treatment (electrocoagulation(EC) and sorption/filtration treatment) with different sequencing to reduce the organic pollutantsm ...