Evaluation of airborne transmission risk in university towns based on IEQ surveys

This study aims to evaluate airborne transmission risk in university towns during the COVID-19 pandemic based on surveys of indoor environmental quality(IEQ).Both on-site measurements and questionnaire surveys were carried out in public buildings in university towns in Changsha,China.Air temperature,relative humidity,and CO 2 concentration in one library,ten classrooms,eight canteens,seven restaurants,and sixteen malls were mea-sured.2220 valid questionnaires concerning occupants’sensation on thermal environment,air movement,and indoor air quality were collected.A 3-level evaluation method of airborne transmission risk that is dependent on building type and indoor CO 2 concentration was developed.Excessive CO 2 concentration is found in library(1045 ppm),classrooms(1151 ppm),restaurants(1242 ppm),and malls(1057 ppm).The percentage time of“high risk”accounts for 18-100%in these buildings.The results reveal a serious problem:numerous public buildings in China and probably other resource limited countries are not basically prepared and equipped to cope with airborne transmission.This fact should be taken into account when developing guidelines and formu-lating mitigation measures.Real-time monitoring and displaying IEQ and thus the transmission risk level should be an important way to be widely implemented in public buildings.

Control for Modified University of Cape Town Process Using Oxidation-Reduction Potential in the Second Anoxic Zone

The aim of this work is to evaluate the feasibility of applying the technology of oxidation-reduction potential （ORP） control on the municipal wastewater treatment system for nitrogen and phosphorus removal. Meanwhile the relation between the optimal ORP （ ORPopt ） and influent C/N ratio was evaluated, in which the influent chemical oxygen demand （ COD ） concentration was stabilized at （290 ± 10 ） mg/L, the influent total phosphorus （TP） concentration was stabilized at （7.0 ± 0.5 ） mg/L. The results indicated that： （1） the ORP in the second anoxic zone had effect on nitrogen and phosphorus removal capability, and the average percentages of phosphorus uptake in ANO2 zone （ ηa ） increased with increasing ORP, i. e. , increasing from 12. 0% at - 143 mV to 22.0%,30.0%,37.0%, and45.0% at -123, -111, -105 and -95 mV, respectively; （2） the ORPopt as function of influent C/N ratio could be calculated by the equation： y ffi 252. 73e〈 -x/3.39） _ 131.01 ; the maximum percentage of phosphorus uptake in ANO2 as function of the ORPopt could be calculated by the equation： y ffi -0.49e（x/15.58） ＋ 1. 51. The ORPopt was the important process control parameter that must be optimized for operation of enhanced biological phosphorus removal （ EBPR ） system. Moreover, ORP sensor is very simple, and the industrial applications of this strategy is practical.