Pre and post-treatment of anaerobic digestion process using hydrodynamic cavitation

Abstract

NaOH for pH adjustment was used and disintegration degree (DD) had 48.4%, HC alone 11.9% and alkaline-only 16.2%. $CH_4$ production was positively influenced with pH increase and the largest amounts of accumulated methane production was 80.7 ml/g $COD_{added}$ at pH 11. However, in such a way that followed by AD, it has the possibility to release high levels of N and P, thus unique status of HC was utilized with struvite precipitation. The highest phosphate removal efficiency was observed at pH 10 with HC, that was twice more than the simple stirring method $(63 mg PO_4^{3-}/L by simple stirring and 150 mg PO_4^{3-}/L by HC)$. It was concluded that HC was both-sided beneficial method when waste sludge needs pre or post-treatments. Livestock wastewater (LW) contains high level of organic compounds and treated by AD. However, high level of ammonia in LW inhibited acidogenesis, resulting in lower digestive ability. Ammonia stripping is one of the positive solution. This process just used for stripping ammonia from the influent, but ammonia stripping combined with HC is expected to provide another benefit. Sludge effectively decomposed by HC (first study), and this method create an atmosphere for intensive ammonia stripping

Low biodegradation of large compounds in hydrolysis step of anaerobic digestion (AD) stands an issue, thus many pretreatments were executed

physical treatments and chemical treatments were adequate to sludge degradation. Hydrodynamic cavitation (HC) was suitable in a powerful and effective manner for sludge disintegration, and performed simultaneously with alkaline catalyst addition

but actually air supply have to be produced. Temperature in liquid increased up to $90^\circ C$ because of continuous cavities collapse. The highest ammonia removal rate was 89% at pH 11 in 90 min, and this result is remarkably improved result compared to other studies. Ammonia also recovered by two successive strong acid bathes. Therefore, application of HC to wastewater treatment both-side profitable method when LW was treated for AD