Impact of sonication on activated sludge properties and consequences on PAH partitioning

Abstract

Sonication is an efficient sludge disintegration technique that can be used for reducing the excess sludge produced in water treatment. The effects of activated sludge sonication on its physicochemical properties and their consequences on the partitioning of hydrophobic polycyclic aromatic hydrocarbons (PAH) are reported. Ultrasound treatment led to an increase in dissolved and colloidal matter in the aqueous phase, with a predominance of proteins compared to the initial supernatant. This transfer of DCM was found to be directly correlated to the energy applied, and resulted in proportional transfer of PAHs from the particulate phase to the aqueous fraction. The PAH aqueous fraction, initially ranging from 0.012 g/g (pyrene) to 0.19 g/g (naphthalene), reached between 0.25–0.37 g/g when a specific energy of 40 000 kJ/kgTS0 was applied. For the raw sludge, the logarithm of the equilibrium constant varied between 3.0–4.3, depending on the hydrophobicity of the molecule, but when sonication was applied, the affinity for particles decreased significantly, resulting in a narrow distribution (log KG = 2.8–3.0 after 40 000 kJ/kgTS0 was applied). PAH partition is governed by molecule hydrophobicity (log Kow) for raw sludge and by sonication intensity for sonicated sludge.

Contemporary Techniques for Remediating Endocrine-Disrupting Compounds in Various Water Sources: Advances in Treatment Methods and Their Limitations

“…The initial primary phase is configured to eliminate the suspended, gross, and floating solids from raw wastewater from its source. It also involves screening to confine solid objects and removal of suspended solids through sedimentation by gravity [ 71 ]. The secondary treatment contains activated sludge, which employs an aeration tank or dispersed-growth reactor containing microorganisms (consuming the organic matter and converting it into carbon dioxide (CO 2 ), water, and energy to enhance reproduction and development), mixed liquor, and a suspension of wastewater.…”

“…Recently, several approaches for the elimination of EDCs from wastewater, including potable water, have been reported. These include the conventional treatment method, adsorption process, biological treatment based on enzymatic degradation, photocatalysis degradation, ozonation and oxidation processes, use of membrane filtration technique, and hybrid systems [24,43,71,72].…”

Nitrite accumulation inside sludge flocs significantly influencing nitrous oxide production by ammonium-oxidizing bacteria

“…Half of the 5.0 mL filtered sample was stored for liquid phase N 2 O measurement using a gas chromatograph (Agilent GC7890A, Agilent Technologies, Santa Clara, California, USA) while the other half for bulk NO 2 -, NH 4 + and NO 3 analyses. The remaining 2.5 mL of the mixed liquor sample was firstly treated with sonication using Branson Sonifier 250 at the maximum amplitude output of as high as 100% for 3 min consistently to release substances accumulating inside sludge flocs to the liquid phase (Mozo et al 2016, Salsabil et al 2009. The…”