Alireza Valipour

Constructed wetlands as sustainable ecotechnologies in decentralization practices: a review

Recently, a range of novel and cost-effective engineered wetland technologies for decentralization practices of domestic wastewater treatment have been developed with ecological process modification, the use of functionalized plants, and advanced biofilm formation. However, selecting the one that can be more appreciated for on-site sanitation is still uncertain. This paper reviews the role of plants, media materials, microorganisms, and oxygen transfer in domestic wastewater purification through constructed wetlands (CWs). The effectiveness of traditional and recently developed CWs and the necessity of an induced biofilm attachment surface (BAS) in these systems for the treatment of domestic sewage are presented. This review also elucidates the idea of CWs for domestic wastewater characteristics highly stressed by total dissolved solids and the adaptive strategies in mitigating the cold climate impacts on their efficiencies. Further research needed to enhance the stability and sustainability of CWs is highlighted. By a more advanced investigation, BAS CWs can be specified as an ideal treatment process in decentralization.

Evaluation of Different Wastewater Treatment Processes and Development of a Modified Attached Growth Bioreactor as a Decentralized Approach for Small Communities

This study was undertaken to evaluate the potential future use of three biological processes in order to designate the most desired solution for on-site treatment of wastewater from residential complexes, that is, conventional activated sludge process (CASP), moving-bed biofilm reactor (MBBR), and packed-bed biofilm reactor (PBBR). Hydraulic retention time (HRT) of 6, 3, and 2 h can be achieved in CASP, MBBR, and PBBR, respectively. The PBBR dealt with a particular arrangement to prevent the restriction of oxygen transfer efficiency into the thick biofilms. The laboratory scale result revealed that the overall reduction of 87% COD, 92% BOD5, 82% TSS, 79% NH3-N, 43% PO4-P, 95% MPN, and 97% TVC at a HRT of 2 h was achieved in PBBR. The microflora present in the system was also estimated through the isolation, identification, and immobilization of the microorganisms with an index of COD elimination. The number of bacterial species examined on the nutrient agar medium was 22 and five bacterial species were documented to degrade the organic pollutants by reducing COD by more than 43%. This study illustrated that the present PBBR with a specific modified internal arrangement could be an ideal practice for promoting sustainable decentralization and therefore providing a low wastage sludge biomass concentration.

Wastewater treatment using integrated anaerobic baffled reactor and Bio-rack wetland planted with Phragmites sp. and Typha sp.

The purpose of this study is to examine the potential use of anaerobic baffled reactor (ABR) followed by Bio-rack wetland planted with Phragmites sp. and Typha sp. for treating domestic wastewater generated by small communities (751 mg COD/L, 500 SCOD mg/L, 348 mg BOD5/L). Two parallel laboratory-scale models showed that the process planted with Phragmites sp. and Typha sp. are capable of removing COD by 87% & 86%, SCOD by 90% & 88%, BOD5 by 93% & 92%, TSS by 88% & 86%, TN by 79% & 77%, PO4-P by 21% & 14% at an overall HRT of 21 (843 g COD/m3/day & 392 g BOD5/m3/day) and 27 (622 g COD/m3/day & 302 g BOD5/m3/day) hours, respectively. Microbial analysis indicated a high reduction in the MPN of total coliform and TVC as high as 99% at the outlet end of the processes. The vegetated system using Phragmites sp. showed significantly greater (p <0.05) pollutant removal efficiencies due to its extensive root and mass growth rate (p <0.05) of the plant compared to Typha sp. The Phragmites sp. indicated a higher relative growth rate (3.92%) than Typha sp. (0.90%). Microorganisms immobilized on the surface of the Bio-rack media (mean TVC: 2.33 × 107 cfu/cm2) were isolated, identified and observed using scanning electron microscopy (SEM). This study illustrated that the present integrated processes could be an ideal approach for promoting a sustainable decentralization, however, Phragmites sp. would be more efficient rather than Typha sp.

Performance evaluation of highly conductive graphene (RGOHI–AcOH) and graphene/metal nanoparticle composites (RGO/Ni) coated on carbon cloth for supercapacitor applications

The application of graphene (RGO)-based composites as electrode materials in supercapacitors can be limited by the fabrication complexity and costs, and the non-environmentally friendly nature of the production process. This study examined the effectiveness of a highly conductive graphene material (RGOHI–AcOH) compared to the hydrazine-produced RGO and graphene nanoparticle composite (RGO/Ni) materials on a carbon cloth substrate in supercapacitors. The composites were synthesized at different mass ratios (1 : 1, 2 : 1, 4 : 1, 10 : 1 and 1 : 2) of RGO to Ni nanoparticles. All synthesized samples were characterized using X-ray diffraction, scanning electron microscopy, atomic force microscopy, X-ray photoelectron spectroscopy and Raman spectroscopy. The methylene blue method was used for determining the specific surface area. The RGOHI–AcOH electrode exhibited a higher electrochemical performance (40 F g−1 at 10 mV s−1 and 70 F g−1 at 0.2 A g−1) and stability (∼94%) than the other electrodes examined. Among the prepared composites, the composite with a RGO to Ni nanoparticle mass ratio of 1 : 1 showed a better electrochemical performance (30 F g−1 at 10 mV s−1, and 27 F g−1 at 0.2 A g−1) than the hydrazine-produced RGO and the other composite electrodes. Overall, RGOHI–AcOH as a first priority electrode material (particularly, coated on a carbon cloth substrate) has potential applications in energy storage devices.

Performance evaluation of the electrolysis process for waste sludge stabilization in decentralization practices

AbstractThis study was undertaken to evaluate the potential use of electrolysis process for waste sludge stabilization in decentralization practices by focusing on the operating parameters such as sludge composition, detention time, and electric voltage. The laboratory batch scale results show that the sludge extracted from a packed bed biofilm reactor can reach the minimum concentration of 659 mg/L volatile suspended solids (VSS) merely within 5 h detention time at an applied voltage of 2 V, whereas the most identical level is obtained from activated sludge by 7 h with 3.6 V. The soluble COD in the supernatant phase of the former process would be increased to 297 mg/L by means of 27% VSS reduction. The economical pre-estimation indicates that electrolysis is more sustainable if stand as a preconditioning stage of biological digestion by 70% capital and operating cost reduction. This configuration can also cause occupying 54% lesser footprint area of aerobic digestion with total average reduction of 56% V...

A Review and Perspective of Constructed Wetlands as a Green Technology in Decentralization Practices

Constructed wetlands (CWs) could be an environmentally acceptable option in treating domestic sewage. But, the successful implementation of this technology in decentralization practices is still under debate. Increasing the knowledge regarding the use of CWs in coastal regions where domestic sewage seriously stressed with total dissolved solids (TDS) and cold weather conditions is additionally imperative. A comprehensive review is therefore needed to have a better understanding of this state-of-the-art technology to inspire a sustainable solution for onsite sanitation. This chapter covers the role of plants, media materials, microorganisms, and oxygen transfer in domestic wastewater purification through constructed wetlands (CWs). The pros and cons, operational design variables, and effectiveness of traditional and recently developed CWs, and the necessity of an induced biofilm attachment surface (BAS) in these systems for the treatment of domestic sewage are presented. This chapter also elucidates the ability of CWs to deal with TDS-contaminated wastewater. Adaptive strategies to mitigate the impacts of cold climate on the effectiveness of CWs are also summarized. Future research that needs for enhancing stability and sustainability of wetland systems is highlighted. Overall, by more advanced investigation, the biofilm attachment surface (BAS) CWs can be specified as an ideal treatment process in decentralization. The success of CWs responding to environmental stress can occur by optimum engineering design and operation.