page_title: Environmental effects of laundry wastewater
section_title: Environmental harm of surfactants
hierarchical_section_title: Environmental effects of laundry wastewater / Mechanism / Environmental harm of surfactants
caption_attribution_description: English: beta oxidation of LAS biogradation
context_page_description: Wastewater comes out of the laundry process with additional energy, lint, soil, dyes, finishing agents, and other chemicals from detergents. Some laundry wastewater goes directly into the environment, due to the flaws of water infrastructure. The majority goes to sewage treatment plants before flowing into the environment. Some chemicals remain in the water after treatment, which may contaminate the water system. Some have argued they can be toxic to wildlife, or can lead to eutrophication.
context_section_description: Surfactants are surface active agents, as they have both hydrophilic and lipophilic; theseperties
  and are widely used in various washing process. With the lipophilic tails, surfactants are biologically active. Anionic surfactants have the ability of binding to bioactive macromolecules like enzymes, DNA, peptides, causing changes of surface charge and the folding of polyp eptide chain(structure o different. Cationic surfactant can bind to the inner membrane of bacteria, and by this way disorganize the bacteria through their long alkyl chain. Nonionic surfactants are able to bind to both proteins and phospholipid membrane, leading to leakage of low molecular mass compounds by increasing the permeability of membranes and vesicles. This may result in serious damage in cells or even cell death.
  —LAS and its biodegradation
  Linear alkylbenzene sulfonate (LAS) with the formula of C₁₂H₂₅C₆H₄SO₃Na, also known as sodium dodecylbenzene sulfonate, is the most widely used anionic surfactant in laundry detergent because it has minimal environmental impact for its readily biodegradation.
  A complete biodegradation under aerobic conditions consists of two steps, primary biodegradation and ultimate biodegradation. The first step begins from the terminal carbon in the alkyl chain as omega-oxidation, which can start from one or both ends, then is followed by beta-oxidation. After the first step the residual is sulfophenyl(di)carboxylates (SP(d)Cs), a large molecule which can be involved in the second step. The second step occurs only when the required bacteria exist. The ring cleavage of benzene and the further desulphonation of the mono- and dicarboxylic sulphophenyl acids happen. After the two-step biodegradation, LAS is degraded into carbon dioxide, water, inorganic salts and residual biomass. During the biodegradation, several specific bacteria and oxygen are required in both omega-oxidation of the alkyl chain and the benzene ring cleaving process, so this biodegradation can only happen in aerobic conditions.  In anaerobic conditions in treatment process, LAS shows no change. Researchers also prove that biodegradation process is restricted in 20–40 mg/L and even inhibited at a higher concentration, which leads to the incomplete biodegradation of LAS in sewage treatment plants.
caption: Beta-oxidation of LAS biodegradation[5]
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