Growth and genetic analysis of Pseudomonas BT1 in a high-thiourea environment reveals the mechanisms by which it restores the ability to remove ammonia nitrogen from wastewater.

Thiourea is widely present in wastewater and can inhibit the nitrification process, inducing the collapse of the nitrification system in sewage treatment plants. Pseudomonas BT1 can restore the ammonia nitrogen removal ability of wastewater treatment processes in which the nitrification system due to thiourea. However, the genetic mechanisms for BT1 are still unclear. In this study, we reported the first genome assembly for Pseudomonas BT1, which has a genome size of 5,576,102 bp and 5,115 predicted genes. Complete C and S metabolic cycles were identified in its genome, and some intersecting intermediate products were found in these cycles. BT1 can grow well and remove ammonia nitrogen at different thiourea concentrations, but it showed a better removal ability in high-thiourea environments. The longest gene activity stage of BT1 was observed in the high-thiourea environments by RNA sequencing, and genes related to maintaining intracellular copper homeostasis were highly expressed during the S metabolism process, which may be the key to restoring the ammonia nitrogen removal ability. Enzymes detected during the N and S cycles showed that BT1 reacts with thiourea to produce hydrogen but not sulphate, suggesting that BT1 may have genes that are involved in thiourea hydrolysis. In conclusion, the high-quality assembly of BT1 provides a valuable resource for analyzing its biological process and molecular mechanisms for thiourea metabolism. BT1 shows great application potential for the removal of thiourea from sewage treatment plants.

Wild Heterotrophic Nitrifying Strain Pseudomonas BT1 Isolated from Kitchen Waste Sludge Restores Ammonia Nitrogen Removal in a Sewage Treatment Plant Shocked by Thiourea.

Thiourea is used in agriculture and industry as a metal scavenger, synthetic intermediate, and nitrification inhibitor. However, in wastewater, it can inhibit the nitrification process and induce the collapse of the nitrification system. In such a case, ammonia-oxidizing bacteria (AOB) lose their ability to remove ammonia. We investigated the nitrification system of a 60,000-t/d municipal sewage treatment plant in Nanjing, which collapsed after receiving 5-15 ppm (5-15 mg/L) thiourea. Ammonia nitrogen removal quickly recovered to more than 95% after inoculation with 10 t high-efficiency nitrification sludge, which was collected from a kitchen waste treatment plant. A heterotrophic nitrification strain was isolated from the inoculated sludge and identified as wild Pseudomonas by 16S rDNA sequencing and named "BT1." Based on thiourea tolerance tests, BT1 can tolerate a thiourea content of more than 500 ppm. For comparison, the in situ process was imitated by the simulation system, and the wastewater shocked by 10 ppm thiourea could still meet the emission standard after adding 1% (V/V) BT1. High-throughput sequencing analysis was applied to study microbial succession during thiourea shock loading. The results showed that Hydrogenophaga and Thiobacillus grew with the growth of BT1. Pseudomonas BT1 was used for a 6,000-t/d printed circuit board (PCB) wastewater treatment system, the nitrification system returned to normal in 15 days, and the degradation rate stabilized at more than 95%.

Polytetrafluoroethylene (PTFE) hollow fiber AnMBR performance in the treatment of organic wastewater with varying salinity and membrane cleaning behavior.

PTFE hollow fiber anaerobic membrane bio-reactor (AnMBR) performance was investigated in the treatment of organic wastewater, with varying salinity and PTFE membrane cleaning behavior. The AnMBR was operated for 226 days, with a total and biological COD removal efficiency of 97.2% and 89.9% respectively, at a NaCl concentration of 35 g L-1. A high number of Proteobacteria (38.2%) and Bacteroidetes (25.9%) were present in the system, with an increase in membrane fouling rate from 1.88 × 1011 to 2.63 × 1011 m-1 d-1 with higher salinity. The effects of soluble microbial products (SMP), extracellular polymeric substances (EPS), low molecular-weight (LMW) carbohydrates, sludge particle size and inorganic element accumulation, were evaluated on membrane fouling. Flux recovery of fouled PTFE membranes reached 91.6% with offline cleaning. Overall, results indicate that PTFE hollow fiber AnMBR provides a promising method for the treatment of saline organic wastewater.