Abstract
With population surge, industrialization and urbanization; use of
surfactants has increased manifold (Das et al., 2019). After their use
in households and industries, surfactants either end up in sewerage
systems or are directly discharged into surface waters. They can hence
be found dispersed in water phase or adsorbed onto aquatic sediments and
sewage sludge. Due to limited metabolic pathways, most of the common
surfactants are not degradable in anaerobic conditions that generally
prevail in sewage ingressed water bodies so sludge accumulated in these
water bodies after the anaerobic digestion process is rich in
surfactants (Ying, 2006). Sediment is a complex mixture of organic
(bacteria, proteins, humic and fulvic acids, humin, etc.) and inorganic
(silica, minerals, metal oxides and hydroxides, aluminosilicates)
components. Absorptivity of surfactant depends on the sorbent
composition and also on the type of surfactant (Ishiguro & Koopal,
2016).
A crucial question related to surfactant absorption is its
reversibility- as to whether the surfactant can desorb. The knowledge of
this can be beneficial in understanding the environmental fate of
surfactants. The presence of surfactants in water bodies can form foams.
Generally, foaming in surface water is a result of a mixture of
surfactants from various sources (Schilling & Zessner, 2011). However,
contribution of sediment as a source of surfactant in a foaming water
body has not been studied adequately. Also, existence of surfactants in
water, beyond certain concentrations not only induces unpleasant taste
and odor, but also causes undesirable changes in the ecosystem. Thus, it
becomes imperative to study the ratio of the surfactant associated with
water, to the extent of surfactant associated the sorbent such as
sediment/sludge to understand the environmental risk associated with
surfactant.
This study aims to understand a foaming urban lake which foams only
after heavy rainfalls. This study tests the hypothesis that surfactants
accumulate in the lake sediment in significant proportions and desorbs
upon dilution occurring due to addition of rainwater into the lake. This
when churned by heavy runoff causes large quantities of stable foam.
This paper aims at analyzing the role of lake sediment in foaming of a
lake.