One-Step Reverse Osmosis Based on Riverbank Filtration for Future Drinking Water Purification

The presence of newly emerging pollutants in the aquatic environment poses great challenges for drink-ing water treatment plants.Due to their low concentrations and unknown characteristics,emerging pol-lutants cannot be efficiently removed by conventional water treatment processes,making technically,economically,and environmentally friendly water purification technologies increasingly important.This article introduces a one-step reverse osmosis(OSRO)concept consisting of riverbank filtration(RBF)and reverse osmosis(RO)for drinking water treatment.The OSRO concept combines the relatively low-cost natural pretreatment of river water with an advanced engineered purification system.RBF pro-vides a continuous natural source of water with stable water quality and a robust barrier for contami-nants.With the pre-removal of particles,organic matter,organic micro-pollutants(OMPs),and microbes,RBF becomes an ideal source for a purification system based on RO membranes,in comparison with the direct intake of surface water.OSRO treatment removes almost 99.9%of the particles,pathogens,viruses,and OMPs,as well as the vast majority of nutrients,and thus meets the requirements for the chlorine-free delivery of drinking water with high biostability.The OSRO treatment is cost effective com-pared with the standard conventional series of purification steps involving sprinkling filters,softening,and activated carbon.Artificial bank filtration(ABF),which functions as an artificial recharge in combi-nation with a sand filtration system,is proposed as an alternative for RBF in the OSRO concept to supply drinking water from locally available resources.It is also suggested that the OSRO concept be imple-mented with wind power as an alternative energy source in order to be more sustainable and renewable.An OSRO-based decentralized water system is proposed for water reclaiming and reuse.It is suggested that future water treatment focus on the combination of natural and engineered systems to provide drinking water through technically efficient,financially feasible,resource reusable,and environmentally relevant means.

Seasonal variations in dissolved organic matter concentration and composition in an outdoor system for bank filtration simulation

Dissolved organic matter(DOM)in surface waters can vary markedly in character depending on seasonal variations such as rainfall intensity,UV radiations and temperature.Changes in DOM as well as temperature and rainfall intensity over the year can affect the biochemical processes occurring in bank filtration(BF).Identification and characterization of DOM in the surface water could help to optimize the water treatment and provide stable and safe drinking water.This study investigated year-long variations of DOM concentrations and compositions in a surface water of a circulated outdoor pond(research facility)connected to a BF passage.DOM was dominated by humic substances and a changing pattern of DOM in surface water was observed throughout the year.A significant increase of DOM(~38%)in surface water was noted in August compared to November.The fluorescent DOM showed that DOM in summer was enriched with the degradable fraction whilst non-degradable fraction was dominated in winter.A constant(1.7±0.1 mg/L)effluent DOM was recirculated in the system throughout the year.DOM removal through BF varied between 4%to 39%and was achieved within a few meters after infiltration and significantly correlated with influent DOM concentration(R^(2)=0.82,p<0.05).However,no significant(p>0.05)change in the removal of DOM was observed in two subsurface layers(upper and lower).This study highlights the presence of a constant non-degradable DOM in the bank filtrate,which was not affected by temperature,redox conditions and UV radiations.