Effects of Temperature and Hydraulic Residence Time (HRT) on Treatment of Dilute Wastewater in a Carrier Anaerobic Baffled Reactor

Objective To examine the effect of hydraulic residence time （HRT） on the performance and stability, to treat dilute wastewater at different operational temperatures in a carrier anaerobic baffled reactor （CABR）, and hence to gain a deeper insight into microbial responses to hydraulic shocks on the base of the relationships among macroscopic performance, catabolic intermediate, and microcosmic alternation. Methods COD, VFAs, and microbial activity were detected with constant feed strength （300 mg/L） at different HRTs （9-18 h） and temperatures （10℃-28℃） in a CABR. Results The removal efficiencies declined with the decreases of HRTs and temperatures. However, the COD removal load was still higher at short HRT than at long HRT. Devastating reactor performance happened at temperature of 10℃ and at HRT of 9 h. HRTs had effect on the VFAs in the reactor slightly both at high and low temperatures, but the reasons differed from each other. Microbial activity was sensitive to indicate changes of environmental and operational parameters in the reactor. Conclusion The CABR offers to certain extent an application to treat dilute wastewater under a hydraulic-shock at temperatures from 10℃to 28℃.

Quantifying the electron-donating and-accepting capacities of wastewater for evaluating and optimizing biological wastewater treatment processes

Biological processes have been widely used for the treatment of both domestic and industrial wastewaters.In such biological processes,pollutants are converted into pollution-free substances by microorganisms through oxidation-reduction reactions.Thus,how to quantify the internal oxidation-reduction properties wastewaters and seek out targeted countermeasures is essential to understand,operate,and optimize biological wastewater treatment systems.So far,no such approach is available yet.In this work,a novel concept of electron neutralization-based evaluation is proposed to describe the internal oxidation-reduction properties of wastewater.Pollutants in wastewater are defined as electron donor substances(EDSs)or electron acceptor substances(EASs),which could give or accept electrons,respectively.With such an electron neutralization concept,several parameters,i.e.,electron residual concentration(R),economy-related index(E and E r),and economical evaluation index(Y and Y r),are defined.Then,these parameters are used to evaluate the performance and economic aspects of currently applied wastewater treatment processes and even optimize systems.Three case studies demonstrate that the proposed concept could be effectively used to reduce wastewater treatment costs,assess energy recovery,and evaluate process performance.Therefore,a new,simple,and reliable methodology is established to describe the oxidation-reduction properties of wastewater and assess the biological wastewater treatment processes.