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.

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.

Phytoconstituents and Biological Activities of Panax vietnamensis (Vietnamese Ginseng): A Precious Ginseng and Call for Further Research-A systematic review

Panax vietnamensis Ha et Grushv., a Vietnamese ginseng, is a well-known plant, naturally distributed in the Ngoc Linh and Hoang Lien Son mountain areas in Vietnam. It is used as a tonic and medicinal food in traditional folk medicine because it possesses wondrous health benefits. To support its functional attributes, various investigations have been carried out to find out its anti-inflammatory, anti-cancer, anti-stress, anti-nociception, psychomotor and sedative-hypnotic effects and anxiolytic activities. Also similar to other ginsengs, Vietnamese ginseng is a rich source of saponins and it has higher content of protopanaxadiol-, protopanaxatrial- and ocotillol-type saponins compared to other ginsengs in the world. Majonoside R2 is a main saponin in Vietnamese ginseng but this compound does not exist in Panax ginseng. Based on this systematic review, we discussed for future prospects and suggest that thorough scientific scrutiny is necessary in future researches.