npj Clean Water

The 2018 edition of the United Nations World Water Development Report stated that nearly 6 billion peoples will suffer from clean water scarcity by 2050. This is the result of increasing demand for water, reduction of water resources, and increasing pollution of water, driven by dramatic population and economic growth. It is suggested that this number may be an underestimation, and scarcity of clean water by 2050 may be worse as the effects of the three drivers of water scarcity, as well as of unequal growth, accessibility and needs, are underrated. While the report promotes the spontaneous adoption of nature-based-solutions within an unconstrained population and economic expansion, there is an urgent need to regulate demography and economy, while enforcing clear rules to limit pollution, preserve aquifers and save water, equally applying everywhere. The aim of this paper is to highlight the inter-linkage in between population and economic growth and water demand, resources and pollution, that ultimately drive water scarcity, and the relevance of these aspects in local, rather than global, perspective, with a view to stimulating debate.

High molecular weight (10⁶–3 × 10⁷ Da) polyacrylamide (PAM) is commonly used as a flocculant in water and wastewater treatment, as a soil conditioner, and as a viscosity modifier and friction reducer in both enhanced oil recovery and high volume hydraulic fracturing. These applications of PAM can result in significant environmental challenges, both in water management and in contamination of local water supplies after accidental spills. This paper provides a short review of current applications of high molecular weight PAM, including the potential for PAM degradation by chemical, mechanical, thermal, photolytic, and biological processes. Methods for treating wastewater containing partially degraded PAM are then discussed along with issues related to the potential toxicity and mobility of PAM in the environment after disposal or accidental release.

Pepper mild mottle virus (PMMoV) was recently found to be the most abundant RNA virus in human feces, and is a plant virus belonging to the genus Tobamovirus in the family Virgoviridae. When in human feces, it is of dietary origin from peppers and their processed products, and is excreted from a large proportion of healthy human populations, but rarely found in animal feces. Over the past decade, this virus has been increasingly attracting research attention as a potential viral indicator for human fecal pollution in aquatic environments and water treatment systems. Results presented in the literature reveal that PMMoV is globally distributed and present in various water sources in greater abundance than human pathogenic viruses, without substantial seasonal fluctuations. Several studies report that increased concentrations of PMMoV tend to be correlated with increased fecal contamination in general, along with more frequent detection of pathogenic enteric viruses. PMMoV also exhibits remarkable stability in water under various environmental conditions. Here, we review recent advancements in our understanding of the occurrence and persistence of PMMoV in natural and engineered water systems and discuss its advantages and limitations as a viral indicator for improved microbial water quality management.

For communities in developing countries, the majority of drinking water-related issues are due to pathogens from poor sanitation, resulting in infection and diarrhea. One cause of this is that these communities often do not have access to centralized water treatment facilities. Point-of-use (POU) systems are key solutions for treating water in developing communities; they are typically user-friendly, low cost, low maintenance, and grid-independent. Importantly, they treat and reduce the number of pathogens in water supplies, and many POU systems have been deployed and used by these communities, improving their livelihood. This review focuses on POU systems that cater to households or communities, with the aim to examine and evaluate technologies that have been implemented in POU systems in the past decade.

The chemical regeneration process has been extensively applied to reactivate biochar, supporting its reusability and leading to significant operating cost reduction. However, no recent review discusses the effectiveness of biochar chemical regeneration. Thus, this article comprehensively reviews the chemical regeneration of biochar contaminated with organic and inorganic pollutants. Performance of the chemical regeneration depends on adsorption mechanism, functional groups, adsorbent pore structure, and changes in active adsorbent sites. Secondary contamination is one of the challenges facing the sustainable adaptation of the chemical regeneration process in the industry. The paper discusses these challenges and draws a roadmap for future research to support sustainable wastewater treatment by biochar.

Ion exchange (IEX) processes are a promising alternative to remove and recover nutrients from municipal wastewater. To assess the feasibility and viability of IEX processes for full-scale application, this study aimed at providing an evaluation of performance and economics on upscaling these processes for two different configurations in a 10,000 population equivalent wastewater treatment plant (WWTP) and compared them with a traditional biological nutrient removal (BNR) plant. The IEX processes were designed based on existing pilot-scale data, and after aerobic or anaerobic carbon removal stages. The nutrients were recovered from spent regenerants in the form of (NH₄)₂SO₄ and hydroxyapatite Ca₅(PO₄)₃(OH), allowing regenerant reuse. The 40-year whole life cost (WLC) of IEX coupled with traditional activated sludge processes was estimated to be ~£7.4 M, and WLC of IEX coupled with anaerobic membrane process was estimated to be £6.1 M, which was, respectively, 17% and 27% less than the traditional BNR based WWTP. Furthermore, ~98 tonnes of (NH₄)₂SO₄ and 3.4 tonnes of Ca₃(PO₄)₂ could be recovered annually. The benefits of lower costs, reduction in greenhouse gas emissions and nutrient recovery aligned with circular economy, illustrated that IEX processes are attractive for nutrient removal and recovery from municipal wastewater.

Nhân loại đang phải đối mặt với thách thức toàn cầu về tài nguyên nước ngày càng cạn kiệt và tình hình trở nên nghiêm trọng hơn do dân số tăng lên dẫn đến ô nhiễm nước quá mức. Nanofiltration là một công nghệ dựa trên màng quan trọng trong việc sản xuất nước sạch và nước uống cho các hoạt động sinh hoạt và công nghiệp. Các màng nanofiltration composite màng mỏng polyamide siêu liên kết (HCPA-TFC-NF) đã được tạo ra bằng cách sử dụng amin đa chức năng 1 (có hai nhóm -NH₂ chính và hai nhóm -NH thứ cấp) và clorua terephthaloyl hai chức năng 2 (TPC) thông qua quá trình polymer hóa giao diện. Cấu trúc mạng polyamide siêu liên kết đã được xác nhận thành công bằng phương pháp NMR carbon-13 rắn (CP-MAS), XPS, AFM, FT-IR, phân tích bản đồ nguyên tố và phân tích EDX. Các đặc tính của màng như hình thái bề mặt và tính ưa nước đã được xác định qua các phép đo FE-SEM và góc tiếp xúc với nước. Phân tích FE-SEM đã tiết lộ sự hình thành lớp hoạt động polyamide đồng nhất trên bề mặt hỗ trợ PS/PET, và cấu trúc lỗ của các màng đã được điều chỉnh bằng cách nghiên cứu ảnh hưởng của nhiệt độ làm cứng và thời gian làm cứng. Các màng nanofiltration đã từ chối hiệu quả một loạt các muối hai hóa trị bao gồm MgCl₂, CaCl₂, Na₂SO₄, MgSO₄, và NaCl bằng cách sử dụng thiết lập lọc dòng chéo. Dựa trên hiệu suất lọc dòng chéo, các điều kiện tốt nhất cho việc chế tạo màng được tìm thấy là nhiệt độ làm cứng 80 °C với thời gian làm cứng 1 h. Tỷ lệ từ chối muối cao nhất được quan sát trong trường hợp MgCl₂ đạt giá trị 98.11% trong trường hợp HCPA-TFC-NF@M3 và được tìm thấy là 97.45% trong trường hợp HCPA-TFC-NF@M2 trong khi mức độ từ chối MgCl₂ đã giảm xuống 94.59% trong trường hợp HCPA-TFC-NF@M1. HCPA-TFC-NF@M2 cho thấy tỷ lệ từ chối NaCl đạt 87.36%. Việc xử lý bằng axit hydrofluoric của HCPA-TFC-NF-M2 đã tăng cường lưu lượng nước trong khi vẫn giữ mức độ từ chối cao. HCPA-TFC-NF@M2 cho thấy tỷ lệ từ chối lớn hơn 99% với EBT và lưu lượng thẩm thấu đạt 75 LMH.

In this study, an electrohydrodynamic atomization or electrospraying technique is used for the uniform deposition of carbon nanotubes (CNT) on a commercially available PTFE membrane and employed for Membrane Distillation (MD) process. Modified PTFE-CNT membrane was characterized for water contact angle, liquid entry pressure (LEP), pore size distribution, and surface morphology. The electrospray coating of CNT on the PTFE membrane enhances the turbulence and thereby the temperature polarization coefficient (TPC). The pore size of the micropatterned PTFE-CNT membrane has been reduced and pore size distribution has been narrowed compared to the PTFE membrane. Field-effect scanning electron microscopy images of the membranes were observed before and after the MD process. Functionally graded PTFE-CNT membrane showed superior desalination performance compared to the PTFE membrane with less amount of cake layer formation on the membrane surface. Water vapor flux remained constant during 24-h continuous MD process operation with 99.99% rejection of inorganic salts.

Heavy metals (HMs) are highly toxic water pollutants abundant in industrial wastewater. Herein, a bis[3-(trimethoxysilyl)propyl]amine (BTMSPA) cross-linked multiwalled carbon nanotube (MWCNT) nanomaterial (CQACNT) was synthesized by silanization of MWCNT-OH followed by grafting of positively charged quaternary ammonium groups (glycidyl trimethyl ammonium chloride (GTMAC)) by an epoxide ring-opening reaction. The composite membranes were prepared by the incorporation of CQACNT into the poly(ether sulfone) (PES) polymer matrix. The CQACNT-6 composite membrane exhibited a 3.5-fold increase in pure water permeability (PWP; 312.8 L m⁻² h⁻¹ bar⁻¹) as compared to the pristine PES (CQACNT-0) membrane (89.6 L m⁻² h⁻¹ bar⁻¹). Moreover, the CQACNT-6 composite membrane showed high HM removal rates (Pb: 89.53%; Ni: 90.42%; Cu: 91.43%; Zn: 91.86%) as compared to the CQACNT-0 membrane (Pb: 39.73%; Ni: 40.32%; Cu: 42.52%; and Zn: 43.91%). After 9 treatment cycles, the CQACNT-6 membrane retained up to 87%, and 94% of its initial PWP and initial Cu²⁺ rejection, respectively, compared to only 58%, and 54%, respectively for pristine CQACNT-0. The positively charged quaternary ammonium groups enhanced the surface features of PES and MWCNTS, resulting in competitive HM removal rates due to the electrostatic repulsion between the HM and the porous membranes, as well as high PWP.