Applying novel methods in conventional activated sludge plants to treat low-strength wastewater

Pilot-scale investigation of performance and microbial community in a novel system combining fixed and suspended activated sludge

The conventional activated sludge (CAS) process is a widely used method for wastewater treatment due to its effectiveness and affordability. However, it can be prone to sludge abnormalities such as sludge bulking/foaming and sludge loss, which can lead to a decrease in treatment efficiency. To address these issues, a novel bag-based fixed activated sludge (BBFAS) system utilizing mesh bags to contain the sludge was developed for low carbon/nitrogen ratio wastewater treatment. Pilot-scale experiments demonstrated that the BBFAS system could successfully avoid the sludge abnormalities. Moreover, it was not affected by mass transfer resistance and exhibited significantly higher nitrogen removal efficiency, surpassing that of the CAS system by up to 78%. Additionally, the BBFAS system demonstrated comparable organic matter removal efficiency to CAS system. 16S rRNA gene high-throughput sequencing revealed that the bacterial community structure within the BBFAS system was significantly different from that of the CAS system. The bacteria associated with ammonium removal were more abundant in the BBFAS system than in the CAS system. The abundance of Nitrospira in the BBFAS could reach up to 6% and significantly higher than that in the CAS system, and they were likely responsible for both ammonia-oxidizing and nitrite-oxidizing functions. Clear stratification of microbial communities was observed from the outer to inner layers of the bag components due to the gradients of dissolved oxygen and other substrates. Overall, this study presents a promising approach for avoiding activated sludge abnormalities while maintaining high pollutant removal performance.

PacBio next-generation sequencing uncovers Apicomplexa diversity in different habitats

The phylum Apicomplexa comprises a large group of intracellular protozoan parasites. These microorganisms are known to infect a variety of vertebrate and invertebrate hosts, leading to significant medical and veterinary conditions such as toxoplasmosis, cryptosporidiosis, theileriosis, and eimeriosis. Despite their importance, comprehensive data on their diversity and distribution, especially in riverine environments, remain scant. To bridge this knowledge gap, we utilized next-generation high-throughput 18S rRNA amplicon sequencing powered by PacBio technology to explore the diversity and composition of the Apicomplexa taxa. Principal component analysis (PCA) and principal coordinate analysis (PCoA) indicated the habitat heterogeneity for the physicochemical parameters and the Apicomplexa community. These results were supported by PERMANOVA (P < 0.001), ANOSIM (P < 0.001), Cluster analysis, and Venn diagram. Dominant genera of Apicomplexa in inlet samples included Gregarina (38.54%), Cryptosporidium (32.29%), and Leidyana (11.90%). In contrast, outlet samples were dominated by Babesia, Cryptosporidium, and Theileria. While surface water samples revealed 16% and 8.33% relative abundance of Toxoplasma and Cryptosporidium, respectively. To our knowledge, the next-generation high throughput sequencing covered a wide range of parasites in Egypt for the first time, which could be useful for legislation of the standards for drinking water and wastewater reuse.

Effect of freshwater and wastewater irrigation on buildup of toxic elements in soil and maize crop

Untreated wastewater is routinely used for agricultural activities in water-stressed regions, thereby causing severe ecological risks by various pollutants. Hence, management strategies are needed to cope with the environmental issues related to wastewater use in agriculture. This pot study evaluates the effect of mixing either freshwater (FW) or groundwater (GW) with sewage water (SW) on the buildup of potentially toxic elements (PTEs) in soil and maize crop. Results revealed that SW of Vehari contains high levels of Cd (0.08 mg L^-1) and Cr (2.3 mg L^-1). Mixing of FW and GW with SW increased soil contents of As (22%) and decreased Cd (1%), Cu (1%), Fe (3%), Mn (9%), Ni (9%), Pb (10%), and Zn (4%) than SW "alone" treatment. Risk indices showed high-degree of soil-contamination and very-high ecological risks. Maize accumulated considerable concentrations of PTEs in roots and shoot with bioconcentration factor > 1 for Cd, Cu, and Pb and transfer factor > 1 for As, Fe, Mn, and Ni. Overall, mixed treatments increased plant contents of As (118%), Cu (7%), Mn (8%), Ni (55%), and Zn (1%), while decreased those of Cd (7%), Fe (5%), and Pb (1%) compared to SW "alone" treatments. Risk indices predicted possible carcinogenic risks to cow (CR 0.003 > 0.0001) and sheep (CR 0.0121 > 0.0001) due to consumption of maize fodder containing PTEs. Hence, to minimize possible environmental/health hazards, mixing of FW and GW with SW can be an effective strategy. However, the recommendation greatly depends on the composition of mixing waters.

Prevalence of enteric viruses in wastewater in Egypt after the COVID-19 pandemic

People's hygienic habits greatly affect the spreading rate of enteric viruses. After the COVID-19 pandemic, many people followed announced precautions and improved their hygienic status to protect themselves from SARS-CoV-2 infection. Here, we studied if this indirectly affected the prevalence of enteric viruses in Egypt. A total of 21 samples (one sample per week) were collected from the Zenin wastewater treatment plant (WWTP) through the period between August 2021 and March 2022. Detection of adenovirus, hepatitis A virus (HAV), and rotavirus showed their presence in 66, 14.3, and 9.5% of the collected samples, respectively. Comparing those percentages to previously published data concerned with the detection of the same viruses from the same WWTP or others revealed a remarkable decrease in the prevalence of the three viruses after the COVID-19 pandemic. This allows the conclusion that safety precautions against SARS-CoV-2 lead indirectly to a reduction of adenovirus, HAV, and rotavirus prevalence rates.