Experimental study on spraying performance of biological pesticides in aerial rotary cage nozzle

Aviation spraying is one of the most important methods for the treatment of forestry pests and diseases,which has a high operation efficiency and effectiveness.The combination of aviation spray and biological pesticides to reduce the impact of pesticide spray on environment has become an important development in the direction of agricultural aviation.In order to explore the effects of aviation spray parameters on particle size distribution and activity retention of biological pesticide droplets,a system of droplets size test and an activity retention rate test system of biological pesticides were constructed.The related experiments were conducted by changing the structural parameters of the rotary cage nozzle(the diameter of nozzle)and the technical parameters of the operation(rotary speed and flow rate).The results showed that the average relative width S of the droplets of the rotary cage nozzle was close to 1,and the droplet distribution was uniform.The influence factors on the particle size distribution of biological pesticide droplets were rotary speed,nozzle diameter,medium and flow rate in descending order.The rotary speed,nozzle diameter,and medium had a significant influence on droplet size distribution.The average activity retention rate of Bacillus thuringiensis was 88.83%,and the germination rate of Beauveria bassiana was 89.80%.The rotary speed had a significant effect on the activity retention rate of bacterial and fungal biological pesticides,and it was negatively correlated.The rotary speed was between 3000-5000 r/min,and the activity retention rate was higher.The research results can provide guidance for spraying biological pesticides in aerial plant protection operations with rotary cage nozzle.

Occurrence,distribution,and potential influencing factors of sewage sludge components derived from nine full-scale wastewater treatment plants of Beijing,China

Millions of tons of waste activated sludge（WAS） produced from biological wastewater treatment processes cause severe adverse environmental consequences. A better understanding of WAS composition is thus very critical for sustainable sludge management. In this work, the occurrence and distribution of several fundamental sludge constituents were explored in WAS samples from nine full-scale wastewater treatment plants（WWTPs） of Beijing, China. Among all the components investigated, active heterotrophic biomass was dominant in the samples（up to 9478 mg/L）, followed by endogenous residues（6736 mg/L）,extracellular polymeric substances（2088 mg/L）, and intracellular storage products（464 mg/L）among others. Moreover, significant differences（p 〈 0.05） were observed in composition profiles of sludge samples among the studied WWTPs. To identify the potential parameters affecting the variable fractions of sludge components, wastewater source as well as design and operational parameters of WWTPs were studied using statistical methods. The findings indicated that the component fraction of sewage sludge depends more on wastewater treatment alternatives than on wastewater characteristics among other parameters. A principal component analysis was conducted, which further indicated that there was a greater proportion of residual inert biomass in the sludge produced by the combined system of the conventional anaerobic/anoxic/oxic process and a membrane bioreactor. Additionally, a much longer solids retention time was also found to influence the sludge composition and induce an increase in both endogenous inert residues and extracellular polymeric substances in the sludge.