Development of microbial fuel cell integrated constructed wetland (CMFC) for removal of paracetamol and diclofenac in hospital wastewater.

Hospital wastewater management has become a significant concern across the globe due to the presence of pharmaceutically active compounds (PhACs) and other toxic substances, which can potentially disrupt ecosystems. The presence of recalcitrant PhACs in hospital wastewater increases the difficulty level for conventional wastewater treatment systems. Furthermore, incorporating advanced oxidation-based treatment systems increase capital and operation costs. To reduce treatment costs, low-cost innovative technology, i.e., composite constructed wetland and microbial fuel cell system (CMFC), has been developed for higher treatment efficiency of PhACs in hospital wastewater along with simultaneous bioelectricity generation as an additional outcome. In this study, influencing operating parameters, such as initial chemical oxygen demand (COD), electrode spacing, and substrate-to-water-depth ratio, were optimized for two plant species: water hyacinth (WH) and duckweed (DW). The optimized systems were run in batch and continuous mode for WH-CMFC and DW-CMFC to treat synthetic hospital wastewater with paracetamol and diclofenac, and the bioelectricity generation was monitored. DW-CMFC system depicted better treatment efficiency and voltage generation as compared to WH-CMFC. In continuous mode, the DW-CMFC system exhibited a removal of 95.3% COD, 97.1% paracetamol, and 87.5% diclofenac. WH-CMFC and DW-CMFC achieved power densities of around 21.26 mW/m2 and 42.93 mW/m2, respectively. The fate of PhACs during and after treatment and toxicity analysis of the transformation products formed were also carried out. Higher bio-electricity generation and efficient wastewater treatment of the DW-CMFC make it a sustainable option for hospital wastewater management.

Application of a new baffled horizontal flow constructed wetland-filter unit (BHFCW-FU) for treatment and reuse of petrochemical industry wastewater.

The shortage of water resources and generation of large quantum of wastewater has posed a significant concern to the environment and public health. Recent research on wastewater treatment has started to focus on reusing wastewater for different activities to reduce the stress on natural water resources. Constructed wetland (CWs) is a low-cost wastewater treatment option. However, some drawbacks include large areal requirements and the need for tertiary treatment units for reusable effluent. In this study, a novel composite baffled horizontal flow CW filter unit (BHFCW-FU) was developed to overcome the drawbacks of the conventional CW. The BHFCW-FU planted with Chrysopogon zizanioides provided a nine times longer flow path, and the adjoined variable depth dual media filter reduced the total area requirement and served as a polishing unit. On average, the BHFCW-FU with horizontal sub-surface flow regime could efficiently remove around 93.93%, 87.20%, and 66.25% of turbidity, phenol, and COD, respectively, from real petrochemical wastewater (initial turbidity: 29.6 NTU, phenol: 4.52 mg/L, and COD: 381 mg/L) and rendered the effluent quality reusable for irrigation, industrial, and other environmental purposes. In synthetic wastewater (initial turbidity: 754 NTU, phenol: 10.87 mg/L, and COD: 1691 mg/L), the removal efficiency of turbidity, phenol, and COD were 99.50%, 93.73%, and 87.05%, respectively. In-depth substrate characterization was done to study the removal mechanism. The developed BHFCW-FU required less space and maintenance, provided reusable effluent, and overcame the drawbacks of conventional CWs. Hence, it may show immense potential as an effective wastewater treatment.

A review on the treatment of septage and faecal sludge management: A special emphasis on constructed wetlands.

The global concern of the pollution of freshwater resources is associated with faecal sludge (FS) disposal, which is an inevitable component of onsite wastewater management mostly in developing countries. The difficulties with its treatment facilities lies in its higher organic content and low dewaterability of various available treatment systems. Moreover, the higher variability in characteristics and quantity of FS generated at different locations creates hindrances in designing the treatment system. Among the several treatment options, the constructed wetlands (CW) are an organic/green approach towards sanitation of FS with low cost and higher efficiency. The present study is an in-depth literature review on the quality and quantity of FS and septage (stabilized FS) in different regions attributed to the wide variability of its characteristics. This paper highlights the treatment of FS in different systems with a special emphasis on CW systems. Different mechanisms and factors affecting the FS treatment efficacy in CW, such as DO/aeration, macrophytes, substrate, CW configuration, and other environmental parameters, have been studied meticulously. The cost analysis revealed CW to be an economic system, and it can enable hybridization with other technologies to develop a complete treatment system with pronounced efficiencies. Several process modifications, such as augmentation with aeration, recirculation, micro-organisms, and earthworms, can enhance the treatment efficacies of CWs. The present review exhibited that the widely used plant species is Phragmites, and the optimum solid loading rate (SLR) range is 50-250 kg TS/m2/yr. The various factors to construct an optimized CW system for FS treatment were attempted, which may bolster the necessary guidelines for field-scale applications.

A review on treatment of petroleum refinery and petrochemical plant wastewater: A special emphasis on constructed wetlands.

Petroleum refinery and petrochemical plants (PRPP) are one of the major contributors to toxic and recalcitrant organic polluted water, which has become a significant concern in the field of environmental engineering. Several contaminants of PRPP wastewater are genotoxic, phytotoxic, and carcinogenic, thereby imposing detrimental effects on the environment. Many biological processes were able to achieve chemical oxygen demand (COD) removal ranging from 60% to 90%, and their retention time usually ranged from 10 to 100 days. These methods were not efficient in removing the petroleum hydrocarbons present in PRPP wastewater and produced a significant amount of oily sludge. Advanced oxidation processes achieved the same COD removal efficiency in a few hours and were able to break down recalcitrant organic compounds. However, the associated high cost is a significant drawback concerning PRPP wastewater treatment. In this context, constructed wetlands (CWs) could effectively remove the recalcitrant organic fraction of the wastewater because of the various inherent mechanisms involved, such as phytodegradation, rhizofiltration, microbial degradation, sorption, etc. In this review, we found that CWs were efficient in handling large quantities of high strength PRPP wastewater exhibiting average COD removal of around 80%. Horizontal subsurface flow CWs exhibited better performance than the free surface and floating CWs. These systems could also effectively remove heavy oil and recalcitrant organic compounds, with an average removal efficiency exceeding 80% and 90%, respectively. Furthermore, modifications by varying the aeration system, purposeful hybridization, and identifying the suitable substrate led to the enhanced performance of the systems.

Influence of Ultrasonic Irrigation and Chloroform on Cleanliness of Dentinal Tubules During Endodontic Retreatment-An Invitro SEM Study.

BACKGROUND: Ultrasonic irrigation has been proved for its remarkable cleaning efficiency in the field of endodontics. But its role in endodontic re-treatment has been understated. There is not much data available to understand the effect of ultrasonic irrigation for the evaluation of cleanliness of dentinal tubules when it is used with or without chloroform, a gutta percha solvent during endodontic retreatment. AIM: To compare the influence of ultrasonic irrigation with syringe irrigation on cleanliness of dentinal tubules after gutta perch removal for endodontic retreatment with or without the use of chloroform a gutta percha solvent using scanning electron microscope (SEM). MATERIALS AND METHODS: Freshly extracted 45 human mandibular premolar teeth for periodontal and orthodontic reasons were taken and were occlusally adjusted to a working length of 19 mm. The root canals of all teeth were prepared chemo mechanically to a master apical file size 40 and were divided in various groups. In Group 1 (n = 5; control group), the canals remained unfilled. In Groups 2 and 3 (n = 20 each), the canals were filled using lateral compaction with gutta-percha and AH plus sealer, removal of root fillings was undertaken after 2 weeks using Gates Glidden drills and H files without chloroform in Group 2 and with chloroform in group 3. The specimen of Group 2 and 3 were further divided into two subgroups I and II (n=10). In subgroup I, irrigation was done using side vented needles and sodium hypochlorite. In subgroup II irrigation was done using passive ultrasonic irrigation with sodium hypochlorite. Thereafter, the roots were split and the sections were observed under SEM. The number of occluded dentinal tubules /total number of dentinal tubules were calculated for the coronal, middle and apical third of each root half. Statistical analysis was performed using one-way ANOVA followed by Tukey's test using standardized technique. RESULT: Results indicated that the cleanest dentinal tubules were found in the control group (Group 1 where the canals were unfilled) followed by the non chloroform group with ultrasonic irrigation (Group 3 subdivision II) followed by chloroform group with ultrasonic irrigation (Group 2 subdivision II), the non chloroform group with syringe irrigation (Group 3 subdivision I) and least cleanliness was found in the chloroform group with syringe irrigation (Group 2 subdivision I). CONCLUSION: Under the limitations of this study it could be concluded that both ultrasonic and syringe irrigation showed cleaner canals when chloroform was not used. Irrigation when done with ultrasonics leads to cleaner tubules than syringe irrigation. Hence, mechanical methods of retrieval in conjunction with use of passive ultrasonic irrigation should be a part of retreatment protocol.