Effect of lactose as a co-substrate in the biodegradation of an anionic surfactant "LAS" by anaerobic digestion

Sodium alkylbenzenesulfonate (LAS) is the most widely used anionic surfactant in the manufacture of commercial detergents due to its excellent detergent properties and low cost. However, they are highly polluting products due to their chemical composition, causing a serious problem of pollution and eutrophication in natural bodies of water, if the amount dumped and the frequency with which they are dumped is taken into account. In addition, damage to health and ecosystems by remaining in the environment for a long time, is a relevant issue of immediate attention. This article presents the results found when using lactose as a co-substrate on the simultaneous biodegradation of the LAS surfactant in an arrangement of UASB-type anaerobic reactors in two stages; with a hydraulic retention time of 0.25 days in the acidogenic reactor in which two surfactant concentration rates were evaluated: 200 f 0.49 mg/L with an organic load of 5.92 f 0.5 KgCOD/m3.d 3. d (experiments II, III and V) and 300 f 0.05 mg/L with organic loading. of 6.8 f 0.11 KgCOD/m3.d 3. d (experiment VI) and of one day, in the methanogenic reactor. The results showed that the acidogenic reactor was able to eliminate COD by 42.24% and biodegrade LAS by 86.65% (experiment V). At 300 mg/L (experiment VI), these values are reduced to 36.6 and 55% respectively. For its part, the methanogenic reactor fed with the effluent of the acidogenic reactor (experiment V) with a lower concentration of COD, LAS and organic load, showed a COD removal and LAS biodegradation efficiency of 83.17 and 13.85% respectively.