Effects of acidic and neutral biochars on properties and cadmium retention of soils

In this study, an acidic biochar and a neutral biochar were applied at 5 wt% into two soils for an 11-month incubation experiment. One Ferrosol soil (Ba) was slightly acidic with low organic matter and the other Dermosol soil (Mt) was slightly alkaline with high organic matter. The acidic (pH = 3.25) wood shaving (WS) biochar had no marked impact on nutrient levels, cation exchange capacity (CEC), pH and acid neutralisation capacity (ANC) of either soil. By contrast, the neutral (pH = 7.00) chicken litter (CL) biochar significantly increased major soluble nutrients, pH, ANC of soil Ba. In terms of C storage, 87.9% and 69.5% WS biochar-C can be sequestrated as TOC by soil Ba and Mt, respectively, whereas only 24.0% of CL biochar-C stored in soil Ba and negligible amount in Mt as TOC. Biochars did not have significant effects on soil sorption capacity and sorption reversibility except that CL biochar increased sorption of soil Ba by around 25.4% and decreased desorption by around 50.0%. Overall, the studied acidic C rich WS biochar held little agricultural or remedial values but was favourable for C sequestration. The neutral mineral rich CL biochar may provide short-term agricultural benefit and certain sorption capacities of lower sorption capacity soils, but may be unlikely to result in heightened C sequestration in soils. This is the first study comprehensively examining functions of acidic and neutral biochars for their benefits as a soil amendment and suggests the importance of pre-testing biochars for target purposes prior to their large scale production

Influence of supporting media in suspension on membrane fouling reduction in submerged membrane bioreactor (SMBR)

In this study, the SMBR was compared in terms of membrane fouling with and without the addition of suspended medium in the membrane reactor. The effectiveness of medium in suspension in submerged membrane bioreactor (SMBR) was evaluated at different filtration flux. The SMBR was operated at a flux of 5-30L/m2h (corresponding hydraulic retention time of 10-1.7h) with and without suspended medium. The suspended medium used in this study was granular activated carbon (GAC; particle size 300-600mm) at air scouring (aeration) rates of 0.5-1.5m3m-2 membrane areah-1. At higher aeration rate of 1.5m3/m2 membrane areah, the effect of flux on membrane resistance was found to be negligible. The reduction of aeration rate from 1.5 to 1.0m3m-2 membrane areah-1 resulted in a sudden rise of TMP. The addition of suspended medium prevented a sudden rise of TMP (total membrane resistance reduced from 51×1011 to 20×1011m-1). The organic removal efficiency remained high irrespective of flux. The molecular weight distribution (MWD) and excitation emission matrix (EEM) analysis of SMBR effluent showed a range of organic (composed of amino acids, biopolymers, humics and fulvic acids type substances) removed by the GAC both by scouring and adsorption mechanisms. © 2011 Elsevier B.V

Influence of hydraulic retention time on the nature of foulant organics in a high rate membrane bioreactor

The influence of hydraulic retention time (HRT) in a submerged hollow fibre membrane bioreactor was studied by conducting experiments at four different HRTs (4, 2, 1.3 and 1h) at room temperature of 25°C. It was found that a shorter HRT led to a higher development of trans-membrane pressure. The highest sludge cake and pore-blocking resistances of 4.02×10 11m -1 and 0.77×10 11m -1 respectively were noted for the shortest HRT (of 1h) application. UV and fluorescence spectroscopy analyses showed that the nature of organics in the biomass and sludge cakes were different. The organic fraction analysis by liquid chromatography with organic carbon detector (LC-OCD) showed a significant amount of biopolymers and a lower amount of humics for longer HRT. © 2011 Elsevier B.V

Removal of organic micro-pollutants by conventional membrane bioreactors and high-retention membrane bioreactors

The ubiquitous presence of organic micropollutants (OMPs) in the environment as a result of continuous discharge from wastewater treatment plants (WWTPs) into water matrices—even at trace concentrations (ng/L)—is of great concern, both in the public and environmental health domains. This fact essentially warrants developing and implementing energy-efficient, economical, sustainable and easy to handle technologies to meet stringent legislative requirements. Membrane-based processes—both stand-alone or integration of membrane processes—are an attractive option for the removal of OMPs because of their high reliability compared with conventional process, least chemical consumption and smaller footprint. This review summarizes recent research (mainly 2015–present) on the application of conventional aerobic and anaerobic membrane bioreactors used for the removal of organic micropollutants (OMP) from wastewater. Integration and hybridization of membrane processes with other physicochemical processes are becoming promising options for OMP removal. Recent studies on high retention membrane bioreactors (HRMBRs) such as osmotic membrane bioreactor (OMBRs) and membrane distillation bioreactors (MDBRs) are discussed. Future prospects of membrane bioreactors (MBRs) and HRMBRs for improving OMP removal from wastewater are also proposed