Applicability of zirconium loaded okara in the removal and recovery of phosphorus from municipal wastewater

© 2019 Published under licence by IOP Publishing Ltd. Recently, there is a new trend to consider wastewater as a precious resource. Since phosphorus is a limited non-renewable element, and MAP (Magnesium Ammonium Phosphate - MgNH4PO4.6H2O) is a valuable slow-release fertilizer, the recovery of phosphorous as MAP has received special attention from scientists all over the world. However, the application of this process with municipal wastewater is still a challenge, due to low concentration of phosphorus and high volume of municipal wastewater. This study investigates the potential of reclaiming MAP from municipal wastewater by combination of adsorption and crystallization. Soybean milk residue (okara) was loaded with Zirconium (Zr) to prepare the adsorbent (ZLO). Adsorption and desorption experiments were conducted in a semi-pilot scale ZLO packed colum system. Effects of P: N: Mg molar ratios, chemical sources and temperature on the formation of MAP were examined in an attempt to identify the optimal crystallization conditions. The attained precipitate was characterized using XRD, SEM, FTIR techniques. It was found that the ZLO packed column adsorption-desorption system could pre-concentrate phosphorus from municipal wastewater up to 28.36 times, fitting well the minimum requirement (50 mg P/L) for the economical MAP recovery. Up to 95.19% of dissolved phosphorus in desorption solution was recovered at pH = 9, Mg: N: P molar ratio = 2:2:1, using a combination of MgCl2.6H2O and NH4Cl. The harvested MAP exhibited high purity (92.59%), high P-availability (89% by mass), and extremely low levels of heavy metals. The results prove that it is viable to recover MAP from municipal wastewater by employing ZLO as adsorbent, followed by crystallization. This paves the way for mining phosphorus from municipal wastewater and reducing okara as an agricultural byproduct in a green way

White hard clam (Meretrix lyrata) shells media to improve phosphorus removal in lab-scale horizontal sub-surface flow constructed wetlands: Performance, removal pathways, and lifespan.

This work examined the phosphorus (P) removal from the synthetic pretreated swine wastewater using lab-scale horizontal sub-surface flow constructed wetlands (HSSF-CWs). White hard clam (Meretrix lyrata) shells (WHC) and Paspalum atratum were utilized as substrate and plant, respectively. The focus was placed on treatment performance, removal mechanisms and lifespan of the HSSF-CWs. Results indicated that WHC-based HSSF-CW with P. atratum exhibited a high P removal (89.9%). The mean P efluent concentration and P removal rate were 1.34 ± 0.95 mg/L and 0.32 ± 0.03 g/m2/d, respectively. The mass balance study showed that media sorption was the dominant P removal pathway (77.5%), followed by microbial assimilation (14.5%), plant uptake (5.4%), and other processes (2.6%). It was estimated the WHC-based bed could work effectively for approximately 2.84 years. This WHC-based HSSF-CWs technology will therefore pave the way for recycling Ca-rich waste materials as media in HSSF-CWs to enhance P-rich wastewater purification

Hybrid use of coal slag and calcined ferralsol as wetland substrate for improving phosphorus removal from wastewater

In this study, natural ferralsol (NF) was calcined to enhance its phosphorus (P) adsorption. The NF and calcined ferralsol at the selected temperature (CF500) were characterized by SEM, FTIR, XRD, XRF and other experiments to elucidate changes in morphology and physicochemical properties. CF500 and coal slag (CS) were examined as wetland media individually and combinedly. The applicability of CF500 and CS as the hybrid media in the lab–scale horizontal sub–surface flow constructed wetlands (HSSF–CWs) was evaluated. It was found that 500 °C was the best calcination temperature of NF for P adsorption. The maximum P adsorption capacity of CF500 (19.4 mg/g) was 60.4 ± 2.2 % greater than that of NF. While isotherm data of P sorption by CF500 were fitted both Langmuir and Freundlich models, the kinetic data was better described by Pseudo-second-order model. Thermodynamic parameters revealed the endothermic and spontaneous nature of the P sorption by CF500. The combination of CF500 and CS leveraged the merits of individual substrates while mitigated their demerits. The optimal mixing ratio of CF500 to CS was 1.25:1 by volume. The hybrid CF500–CS substrate HSSF–CWs demonstrated satisfactory P removal efficiency (99.44% ± 0.1) and effluent P concentration (0.08 ± 0.01 mg/L). Application of the mixed substrate in the HSSF–CWs resulted in negligible side effects on their effluent quality. Due to abundant availability of raw materials, simplicity of preparation, as well as efficiency and safety of application, a mixture of CF500 and CS is a promising hybrid substrate in HSSF–CWs for P–rich wastewater decontamination

White hard clam (Meretrix lyrata) shells as novel filter media to augment the phosphorus removal from wastewater.

It is well recognized that filter media play a crucial role in constructed wetlands (CWs) for decontamination of phosphorus (P)-rich wastewater. This study investigates the suitability of raw white hard clam shells (WHC) and white hard clam shells thermally modified at 800 °C (WHC-M800) as potential media to enhance P treatment performance in CWs. The results indicated that both WHC and WHC-M800 displayed appropriate physicochemical properties, such as high porosity, excellent hydraulic conductivity, and rich Ca content. WHC-M800 exhibited a superior P adsorption capacity (38.7 mg/g) to WHC (12.8 mg/g). However, the practical utilization of WHC-M800 as filter media in CWs may be compromised, due to certain limitations, for example: extremely high pH values in the post-adsorption solutions; high weight losses during calcination and adsorption processes; low mechanical strength; and intensive energy consumption. In contrast, the WHC demonstrated significant advantages of reasonably high P adsorption capacity, locally abundant availability, low cost, and marginal side effects. The fractionation of inorganic P of WHC and WHC-M800 revealed that Ca-bounded P was the most dominant binding form, followed by loosely bound P, Fe-P, occluded P, and Al-P. The present study demonstrates that recycling of WHC shells as a potential substrate in CWs provides a feasible method for upgrading P removal in CWs. Additionally, it helps to reduce waste WHC shells in a simple, cheap, and eco-friendly way, thus can double environmental benefits

Resistance mechanisms and genetic relatedness among carbapenem-resistant Pseudomonas aeruginosa isolates from three major hospitals in Hanoi, Vietnam (2011–15)

Background MDR bacteria including carbapenem-resistant Pseudomonas aeruginosa are recognized as an important cause of hospital-acquired infections worldwide. This investigation seeks to determine the molecular characterization and antibiotic resistance genes associated with carbapenem-resistant P. aeruginosa. Methods We conducted WGS and phylogenetic analysis of 72 carbapenem-resistant P. aeruginosa isolated from hospital-acquired infection patients from August 2011 to March 2015 in three major hospitals in Hanoi, Vietnam. Results We identified three variants of IMP gene, among which blaIMP-15 was the most frequent (n = 34) in comparison to blaIMP-26 (n = 2) and blaIMP-51 (n = 12). We observed two isolates with imipenem MIC >128 mg/L that co-harboured blaIMP-15 and blaDIM-1 genes and seven isolates (imipenem MIC > 128 mg/L) with a blaKPC-1 gene from the same hospital. MLST data shows that these 72 isolates belong to 18 STs and phylogenetic tree analysis has divided these isolates into nine groups. Conclusions Our results provide evidence that not only blaIMP-26 but other IMP variants such as blaIMP-15 and blaIMP-51 genes and several STs (ST235, ST244, ST277, ST310, ST773 and ST3151) have been disseminating in healthcare settings in Vietnam. In addition, we report the emergence of two isolates belonging to ST1240 and ST3340 that harboured two important carbapenemase genes (blaIMP-15 and blaDIM-1) and seven isolates belonging to ST3151 of P. aeruginosa that carried the blaKPC-1 gene in Vietnam, which could potentially cause serious restricted availability of treatment options in healthcare settings