Effect of carbon-to-nitrogen ratio on high-rate nitrate removal in an upflow sludge blanket reactor for polluted raw water pre-treatment application
Document Type
Article
Publication Date
3-25-2021
Abstract
The drinking water treatment plants (DWTPs) in the developing countries urgently need an efficient pre-treatment for nitrate (NO3-) removal to cope with the increasing NO3- pollution in raw water. An upflow sludge blanket (USB) reactor applied for NO3- removal from domestic wastewater may be adopted by the DWTPs. However, studies on the optimal carbon-to-nitrogen ratio (C/N) and operation of USB reactor at short hydraulic retention times (HRT) for high-rate polluted raw water pre-treatment are lacking. In this study, we first investigated the optimal C/N for biological NO3- removal in a sequencing batch reactor (SBR). An USB reactor was then operated with the optimal C/N for pre-treating synthetic raw water contaminated with NO3- (40mgNL(-1)) to monitor the NO3- removal performance and to examine opportunities for reducing the HRT. After operating the SBR with designed C/N of 4, 3 and 2g C g(-1) N, we selected C/N of 3g C g(-1) N as the optimal ratio due to the lower carbon breakthrough and nitrite (NO2-) accumulation in the SBR. The USB reactor achieved complete NO3- and NO2- removal with a lower designed C/N of 2g C g(-1) N due to the longer sludge retention time when compared with that of SBR (10 d). The high specific denitrification rate (18.7 +/- 3.6mgNg(-1) mixed liquor volatile suspended solids h(-1)) suggested a possible HRT reduction to 36min. We successfully demonstrated an USB reactor for high-rate NO3- removal, which could be a promising technology for DWTPs to pre-treat raw water sources polluted with NO3-.
Keywords
Denitrification, Hydraulic retention time, Nitrate contamination, Sequencing batch reactor, Sludge retention time
Divisions
fac_eng
Funders
Ministry of Higher Education Malaysia Fundamental Research Grant Scheme[FRGS/1/2017/TK02/UM/02/10],Ministry of Higher Education Malaysia Fundamental Research Grant Scheme[FP047-2017A]
Publication Title
Sustainable Environment Research
Volume
31
Issue
1
Publisher
BMC
Publisher Location
CAMPUS, 4 CRINAN ST, LONDON N1 9XW, ENGLAND