Comparative study of the effect of rice husk-based powders used as physical conditioners on sludge dewatering

Application of skeleton builders to sludge dewatering and disposal: A critical review

With the development of cities and population, the production of sludge is increasing annually. It has become an unavoidable challenge to achieve sludge dewatering and disposal by a cost-effective, efficient and safe process. In this work, firstly, the factors limiting sludge dewatering are reviewed in terms of moisture distribution, sludge concentration, organic matter content, electronegativity, floc strength, and extracellular polymers (EPS). Subsequently, focusing on the dewatering technology about the skeleton builder, the recent progress of it is detailed in terms of mechanism, evaluation indicators, influencing factors, and technology coupling. In addition, the impact of skeleton builders on the sludge disposal stage is concluded. Finally, the challenges faced by sludge dewatering and skeleton builders are prospected. This review will provide some theoretical basis and technical guidance for subsequent experiments and practices regarding skeleton builders.

Application of coffee ground-based skeleton builder with FeCl3 for conditions of pre-dewatered sludge toward further deep dewatering

Skeleton builders are essential for achieving deep sludge dewatering. In this study, a novel spent coffee ground (SCG)-based skeleton builder was developed to attain deep sludge dewatering by combined conditioning with FeCl3, and possible mechanisms were examined. Through different surface analysis techniques, it was demonstrated that at a pyrolysis temperature of 300 °C, the spent coffee ground biochar (SCGB-300) has an intact pore structure, a rigid carbon skeleton, and large oxygen-containing functional groups, making it the best skeleton builder for sludge dewatering. When combined with FeCl3 for conditioning, the structure of SCGB-300 remained intact under high pressure and played important role. The rich porous structure facilitated water drainage. During the sludge conditioning, small amount of positive charge on the surface of SCGB-300 further increased the zeta potential of sludge through charge neutralization. At the same time, the adsorption of SCGB-300 removed viscous hydrophilic substances and further improved the dewatering performance. At an optimum dosage of 6% (dry solid, DS) FeCl3 and 30% SCGB-300 (DS), the moisture content of sludge was reduced from 85.47% to 63.35%, and the dewatering rate was increased from 46.08% to 70.03%. Therefore, SCGB is a promising skeleton builder for sludge conditioning and deep dewatering.

New biopolymer from biomass for conditioning and dehydration of sewage sludge: application on the sludge of Bouira WWTP

Sewage treatment plants in Algeria produce huge quantities of sludge expressed in tons annually. This sludge produced is unfortunately contaminated because of the use of synthetic polyelectrolytes. Recently several kinds of research have been carried out on natural flocculants for sludge conditioning, because of several advantages they present such as their renewable source and their non-toxicity. This work aims to evaluate the potential use of protonated pectin extracted from orange waste of N'GAOUS juice factory as an eco-friendly flocculant in the chemical conditioning of sludge. Protonated pectin effectiveness was compared with synthetic cationic anionic and ionic polyelectrolytes (SUPERFLOC 8396, AF400, NF102). In this context, raw sludge samples from Bouira WWTP were tested. Specific resistance to filtration (SRF), cakes dry solid content were analyzed to determine filterability, dewatering capacity of conditioned sludge, and the optimum dose of each conditioner. So that our goal was to obtain greater dryness, which is the case with the addition of protonated pectin and even the addition of Superfloc, which allowed us to obtain dryness of 33.01% and 29.19%, respectively, for the same doses that gave the lowest SRF. Based on the results found and the analysis of the specific resistance to filtration (SRF) and the dryness, and compared with the values observed for the dewatered sludge by the method used in the Bouira WWTP. Band filters (18-22%) and raw sludge (4.8-5.7%).

Community Composition and Function of Bacteria in Activated Sludge of Municipal Wastewater Treatment Plants

Municipal wastewater treatment plants (WWTPs) use functional microorganisms in activated sludge (AS) to reduce the environmental threat posed by wastewater. In this study, Illumina NovaSeq sequencing of 16S rRNA genes was performed to explore the microbial communities of AS at different stages of the two WWTP projects in Shenzhen, China. Results showed that Proteobacteria, Bacteroidetes, Acidobacteria, Firmicutes, and Nitrospirae were the dominant phyla in all the samples, with Proteobacteria being the most abundant and reaching a maximum proportion of 59.63%. There was no significant difference in biodiversity between the two water plants, but Stage 1 and Stage 2 were significantly different. The Mantel test indicated that nitrate, total nitrogen (TN), chemical oxygen demand (COD), and nutrients were essential factors affecting the bacterial community structure. FAPROTAX analysis emphasized that the leading functional gene families include nitrification, aerobic nitrite oxidation, human pathogens, and phototrophy. This study reveals changes in the community structure of AS in different treatment units of Banxuegang WWTP, which can help engineers to optimize the wastewater treatment process.