The Effect of Different Sludge Pretreatment Methods on Microalgae Performance and the Release of Pollutants in Hydrolysis Acidification Solutions

Abstract

Waste-activated sludge disposal has now become a serious global problem. After pretreatment, sludge was hydrolyzed and acidified to release nutrients. The effects of different sludge pretreatments on microalgal growth and contaminants in a hydrolysis acidification solution were compared. Alkalinization (NaOH), ultrasound (US), and combined pretreatment techniques (US-NaOH) all promoted contaminants’ release from the sludge by triggering microbial cell wall rupture and extracellular polymer dissolution. The organics released from the pretreated sludge were more readily and rapidly consumed due the presence of abundant microorganisms. The US group was more capable of releasing contaminants than the NaOH group, while the US-NaOH group overrode both. The growth characteristics, photosynthetic performance, and effluent treatment properties of Chlorella were observed in all group. In the untreated group, Chlorella exhibited higher algal density, maximum photochemical quantum yield, and effluent treatment capacity. The results demonstrated that sludge pretreatment could facilitate the release and rapid consumption of pollutants. Additionally, the NaOH pretreatment could remove the refractory organics to a higher degree, and could also accumulate more photosynthetic pigments. This study demonstrated the feasibility of Chlorella being used in practical scenarios such as hydrolytic acidification solutions for different sludge treatment methods, providing data for wastewater treatment and resource utilization.