Study on Water Purification Effect and Operation Parameters of Various Units of Wastewater Circulation

Effects of methomyl on the intestinal microbiome and hepatic transcriptome of tilapia, and the modifying effects of mint co-culture

Methomyl (MET) is an oxime carbamate insecticide that can contaminate aquatic systems resulting in toxicological effects. It can harm some fish species possibly through the anti-oxidative, phagosome pathway. Mint is one of the most widely herbal plants exhibiting antioxidant activities. In this study, we investigated the impact of MET on the antioxidant system of Oreochromis niloticus in presence of mint as a floating bed. Results revealed that the superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase, and glutathione S-transferase significantly decreased and the GSH content significantly increased in the intestine. The hepatic peroxisome proliferator-activated receptor (PPAR) signalling pathway, carbon metabolism, renal phosphoinositide 3-kinase (PI3K)-Akt, mitogen-activated protein kinase (MAPK) signalling pathway, and phagosomes were significantly affected. Upon long-term exposure, circadian rhythm and phagosomes were enriched in the liver and kidney. However, mint increased the enriched pathways of Toll-like receptor, PPAR, p53, NF-kappa B, MAPK, oestrogen, and B cell receptor signalling pathways. MET with different concentrations destroyed the balance of gut microbiota, mint decreased Verrucomicrobia and Akkermansia for the maintenance resulted from MET. Cetobacterium had a positive impact on total nitrogen (TN), chemical oxygen demand (CODMn), and glutathione reductase (GR), while Akkermansia had a positive impact on feed conversion ratio (FCR), SOD and CAT, and the abundance of both decreased due to MET exposure. High mint density removed more concentrations of nitrogen and phosphorus in the tilapia cultivation wastewater. Therefore, planting with mint can alleviate the toxicological effects produced by MET, shape the intestinal microbiota, and strengthen the connection between water quality and the metabolic parameters.

Characterization and Adsorption Capacity of Modified Biochar for Sulfamethylimidine and Methylene Blue in Water

In this study, a composite of pond mud and lanthanum- and nano-zero valent iron-modified-biochar was investigated for its ability to adsorb methylene blue (MB) and sulfamethazine (SMZ). La-modified attapulgite and nano-zero valent iron (surface area enhanced by 43.7% via Brunauer-Emmett-Teller analysis) were successfully loaded onto the straw-sediment biochar (BC) surface. With the increase in pyrolysis temperature, the biocompatibility yield, the H, O, and N content, and the ratio of carbon elements decreased, while the pH value, surficial micropores, C element, and ash content increased. The biocarbon small molecules were gradually and tightly ordered, and the organic groups such as hydroxyl, carboxyl groups, and carbon oxygen double bonds were gradually lost or disappeared. The original Fe-BC had more phenolic hydroxyl groups forming an intermolecular hydrogen bond than others with a higher adsorption capacity possibly through the Schiff base reaction. The effect of various pH (2-9), temperature (15-35 °C), and initial concentration (1-25 mg L-1) on adsorption was investigated. pH and temperature were the main factors governing the adsorption process. The maximum adsorption capacity was observed at pH 4. The adsorption performances for MB followed the order Fe-BC > La-BC > BC, and the maximum removal rate was over 98.45% with pH = 7. The three types of BC dosages between 0.2 (6.67 g L-1) and 0.4 g showed a removal rate of 99% for MB. The adsorption capacity of Fe-BC, La-BC, and BC for MB was 2.201, 1.905, and 2.401 mg L-1 with pH = 4, while 4.79, 4.58, and 5.55 mg g-1 were observed with BC dosage at 0.025 g. For SMZ, the higher the temperature, the better the adsorption effect, and it reaches saturation at approximately 25 °C. To further evaluate the nature of adsorption, Langmuir/Freundlich/Temkin models were tested and the adsorption capacities were evaluated on the surface of the BC composite. The three modified materials were physisorbed to SMZ, while MB was chemisorbed. For MB, the adsorption performance of BC is the best < 0.2 g (6.67 g L-1) at pH 7.0 at 35 °C. The Elovich model was more suitable for MB, while the Freundlich and Temkin models could better fit the adsorption process of MB. The preparatory secondary dynamics equation and Langmuir equation were more compliant for SMZ, and the saturated adsorption capacities of straw-modified, La-BC, and Fe-BC reached 5.699, 6.088, and 5.678 mg L-1, respectively.

Effective mechanisms of water purification for nitrogen-modified attapulgite, volcanic rock, and combined exogenous microorganisms

The study tested the water purification mechanism of the combination of microorganisms and purification materials via characteristic, enzymatic, and metagenomics methods. At 48 h, the removal rates of total nitrogen, total phosphorous, and Mn chemical oxygen demand in the combination group were 46.91, 50.93, and 65.08%, respectively. The alkaline phosphatase (AKP) activity increased during all times tested in the volcanic rock, Al@TCAP, and exogenous microorganism groups, while the organophosphorus hydrolase (OPH), dehydrogenase (DHO), and microbial nitrite reductase (NAR) activities increased at 36-48, 6-24, and 36-48 h, respectively. However, the tested activities only increased in the combination groups at 48 h. Al@TCAP exhibits a weak microbial loading capacity, and the Al@TCAP removal is primarily attributed to adsorption. The volcanic rock has a sufficient ability to load microorganisms, and the organisms primarily perform the removal for improved water quality. The predominant genera Pirellulaceae and Polynucleobacter served as the sensitive biomarkers for the treatment at 24, 36-48 h. Al@TCAP increased the expression of Planctomycetes and Actinobacteria, while volcanic rock increased and decreased the expression of Planctomycetes and Proteobacteria. The growth of Planctomycetes and the denitrification reaction were promoted by Al@TCAP and the exogenous microorganisms. The purification material addition group decreased the expression of Hyaloraphidium, Chytridiomycetes (especially Hyaloraphidium), and Monoblepharidomycetes and increased at 36-48 h, respectively. Ascomycota, Basidiomycota, and Kickxellomycota increased in group E, which enhanced the nitrogen cycle through microbial enzyme activities, and the growth of the genus Aspergillus enhanced the phosphorous purification effect.