Solid particle sedimentation is assumed to be a complex procedure in water and wastewater treatment plants. There is great interest in applying and developing different simulation and optimization methods to design primary sedimentation tanks (PSTs). In traditional techniques, mechanical and physical parameters are set by sequential error loops. This study proposes a hybrid method based on the response surface methodology, efficient metaheuristics, and scenario building methods using different experimental methods to eliminate the disadvantage of existing techniques. This novel framework creates a robust and sustainable design for the PSTs. First of all, the parameters of the considered PST, based on the economic, improve process and tank efficiency scenarios are tuned and optimized by the central composition design and response surface methodology. To forecast an efficient response value for these scenarios, different metaheuristic algorithms, including the genetic algorithm (GA), pattern search algorithm (PSA), and simulate annealing algorithm, are applied. Results demonstrated that PSA, GA, and PSA with 0.02, 0.032, and 0.063 compared to experimental practices have the best calibration for predicting response in economic, improved process and tank efficiency scenarios, correspondingly. Finally, experimental tests have proven that the optimum Retention Time is equal to 2 h based on the biological oxygen demand and the total suspended solids eliminations in the laboratory-scale setup. 

/pdf/an-efficient-design-of-primary-sedimentation-tanks-using-a-1tobqmoy.pdf

An efficient design of primary sedimentation tanks using a combination of the response surface, metaheuristic, and scenario building methods

Wastewater treatment plants require long installation and start-up times. In this study, a compact package-type down-flow hanging sponge (DHS) operating system based on the trickling filter principle using polyurethane sponge media was designed and installed at a sewage treatment site in Thailand. The DHS system was installed within 14 d of material arrival and operated for 81 d without seed sludge inoculation. The T-BOD concentration of the DHS effluent reached 2.2 mg·L−1 after 6 d of operation. High nitrification activity of the DHS reactor, when operated with a hydraulic retention time of 3.7 ± 0.9 h, was observed after 13 d of operation. In addition, the DHS effluent achieved the discharge standard within 14 d of operation. The DHS reactor rapidly initiated the removal of organics and nitrogen and exhibited COD, TSS, and ammonia removal efficiencies of 58% ± 10%, 76% ± 21%, and 66% ± 32%, respectively. Parallel 16S rRNA gene sequencing of sludge revealed the rapid growth of nitrifying bacteria. The abundance of ammonia-oxidizing bacteria Nitrosomonas spp. ranged from 0.1% to 1.8% on day 18, indicating that the DHS sponge media effectively retained slow-growth nitrifying bacteria that were affected by the rapid start-up process. Nitrite-oxidizing Nitrospira sp. was mainly detected at the bottom of the reactor. These results show that the compact package-type DHS system is a novel and practical easy-contract sewage treatment method. 

Performance evaluation of quick and compact package-type down-flow hanging sponge system for domestic sewage treatment

A sponge moving bed membrane bioreactor (SMB‐MBR) was developed for high‐rate biological purification of polluted surface water for nonpotable utilization purposes. The SMB‐MBR contains polyurethane sponge cubes (10% v/v) and submerged hollow fibre membranes in a solid separation compartment and operated under a short hydraulic retention time of 1 h. High organic (96% biochemical oxygen demand [BOD], 85% soluble chemical oxygen demand [COD] and 84% COD) and nitrogen (99% ammonium nitrogen [NH4+], 98% total Kjeldahl nitrogen [TKN] and 87% total nitrogen [TN]) removals were achieved. In the SMB‐MBR, the suspended and attached biomass were allowed to develop under no sludge wastage operation. The co‐existence of heterotrophs, nitrifiers and denitrifiers in the biomass was confirmed under a high oxygen environment. Sustainable operation of SMB‐MBR could be achieved by maintaining stable membrane flux without chemical cleaning for 60 days. This research demonstrates the technical feasibility of applying the SMB‐MBR for clean water production when the polluted surface is the only raw water source.

Purification of polluted surface water by sponge moving bed membrane bioreactor with short hydraulic retention time operation

Moringa oleifera (MO), also known as drumstick tree, has gained worldwide attention among researchers and policy makers, for showing its remarkable potential in environmental management. Recently, MO seed or press cake (a by-product of oil extraction industry) powder has also emerged as an alternative and promising coagulant for environmental remediation. In this view, attempts have been made in this study to evaluate the efficacy of MO seed and press cake powder (MSP & PCP) for the treatment of municipal wastewater. Both MSP and PCP are characterized by using swelling ratio, scanning and transmission electron microscopy analysis. The effect of various operational parameters such as coagulation–flocculation pH (2–10), coagulant dosage (0.1–1 g L−1), and sedimentation time (0–180 min), etc., is investigated to understand the potential of MSP and PCP. At optimized operational conditions, sedimentation kinetics is also performed suggesting that the treatment process is being governed by the second-order kinetic model. The chemical and biological oxygen demand removals at optimized conditions are observed as follows: ≈38 and ≈73% for MSP and ≈47 and ≈85% for PCP. Overall, the results of the present study elucidated that PCP can be employed as a promising alternative of MSP for municipal wastewater with improved treatment efficiencies. 

Municipal Wastewater Treatment using
 Moringa oleifera
 Seed and Press Cake Powder: A Comparative Analysis

In order to understand the mechanisms of microbial growth on waste polyurethane sponge materials, their effectiveness as biomass carriers in domestic sewage with increased ammonium nitrogen content treatment was assessed. Comparative experiments were carried out in microreactors under steady conditions of batch culture, which allowed for an assessment of different carriers, in the form of flexible foams, rigid foams, and flexible foams placed in full casings. In the studies conducted in continuous cultures, biomass carriers selected in batch culture were used as fillings in the column model. The structure of the microbial community inhabiting the spongy material was determined and the pollutant-removing process from real domestic sewage was assessed. Analyzes using the Illumina sequencing technique allowed for demonstrating that Nitrosomonas and Nitrospira were the predominant nitrifiers in the biomass carrier in the form of waste polyurethane foams (PUF). It was found that anammox bacteria, the presence of which—as unidentified Planctomycetes—was confirmed in the polyurethane sponge material, were also responsible for the high removal of N-NH4+. Burkholderia and Sphingopyxis phyla were identified as the dominant denitrifying bacteria involved in the treatment of domestic sewage with increased content of ammonium nitrogen. The biomass carrier in the form of waste PUF placed additionally in full casings proved to be more beneficial for the proliferation of bacteria involved in nitrification and denitrification processes. On the other hand, waste foams without casings proved to be more suitable for the growth of microorganisms known to perform partial denitrification and may accumulate nitrites (Staphylococcus, Dokdonella). Additionally, the presence of Devosia and Pseudonocardia, which participated in the phosphorus removal process, was found in the waste PUR foams.

https://www.mdpi.com/1996-1944/16/2/619/pdf?version=1673248665

Waste Polyurethane Foams as Biomass Carriers in the Treatment Process of Domestic Sewage with Increased Ammonium Nitrogen Content

Down-flow hanging sponge (DHS) reactor that is sponge-based trickling filter was considered to be an alternative aerobic treatment system for low strength sewage treatment under tropical conditions...

Efficiency of High Rate Treatment of Low-strength Municipality Sewage by a Pilot-scale Combination System of a Sedimentation Tank and a Down-flow Hanging Sponge Reactor.

Watcharapol Khotwieng

Papers

Efficiency of High Rate Treatment of Low-strength Municipality Sewage by a Pilot-scale Combination System of a Sedimentation Tank and a Down-flow Hanging Sponge Reactor.