Improving Water Quantity and Quality Supply Security by Managed Artificial Recharge Technologies in the Lower Llobregat Aquifers Integrated into a Conjunctive Surface and Groundwater Management Scheme for Barcelona,Spain

The large concentration of human population,industry and services in the Metropolitan Area of Barcelona has to confront scarce water resources,serious seasonal and inter-annual variations and quality deficiencies in the sources.A large fraction of these water resources are in the medium-size Llobregat River basin and the remaining ones correspond to a surface water transfer,seawater desalination and wastewater reclamation.Groundwater dominated water resources availability before 1950.Afterwards,water supply has evolved progressively to integrated water resources management,which includes serious water quality concerns to deal with population density,river pollution,seawater intrusion in the main aquifer,and brine generation in the mid Llobregat basin due to old mining of saline minerals.The role of the alluvial aquifers has progressively evolved from being the main water source to reserve storage to cope with seasonal and drought water resources availability.River-enhanced recharge and artificial recharge are needed to assure enough groundwater storage before surface water becomes scarce and/or suffers a serious temporal loss of quality.Enhanced river recharge started in 1950.Treated river water injection in dual-purpose wells was put into operation in the early 1970s.Basin and pond recharge was added later,as well as a deep well injection barrier along the coast to reduce seawater intrusion and to allow increased groundwater abstraction in moments of water scarcity.There is a progressive evolution from solving water quantity problems to consideration of water quality improvement during recharge,with attention to emergent concern pollutants in river water and in reclaimed water to be considered for artificial recharge.Improvement of artificial recharge operation activities has been introduced and research is being carried out on the difficult behavior to degrade organic pollutants during infiltration and in the terrain.This paper presents the different activities carried out and presents the research activities,and comments on the economic,social and administrative issues involved as well.

新型水循环之海水冲厕的可持续应用

水安全日益严重地威胁着全人类的健康和福祉。因此,寻找可持续替代的水资源已成为一个亟待解决的问题。尽管海水淡化和污水回用在一定程度上可以缓解城市的用水紧张,但是这两项技术的高能耗和高费用阻碍了它们的广泛应用。其实,城市用水中20%30%是用于冲洗厕所,经过简单处理后的海水完全可以达到冲厕用水的水质要求。当然海水冲厕和再生水冲厕一样需要配备单独的管道系统。本文通过生命周期评估和敏感性分析方法,在与常规淡水系统进行比较的基础上,系统地研究了海水冲厕、海水淡化以及污水回用这三种替代水资源的方法,在城市水系统中的相对节约淡水的潜力、对环境的影响以及广泛应用的前景。结果表明,海水冲厕具有环境可持续性,其应用主要取决于城市的有效人口密度和距海岸的距离。在有效人口密度超过3000人·km–2及距海岸30 km以内的沿海城市,海水冲厕所带来的总环境影响明显低于其他两个替代水资源。如进一步结合应用适合含盐污水处理的硫酸盐还原、自养反硝化和综合硝化(sulfate reduction,autotrophic denitrification,and nitrification integrated,SANI)处理技术,海水冲厕的潜在应用范围可以扩大到距海岸60 km的沿海城市。对于符合这些要求的沿海城市,建议将海水冲厕纳入城市水系统,从而促进城市水循环的可持续发展。

A “Seawater-in-Sludge” approach for capacitive biochar production via the alkaline and alkaline earth metals activation

Sewage sludge is a potential precursor for biochar production,but its effective utilization involves costly activation steps.To modify biochar properties while ensuring cost-effectiveness,we examined the feasibility of using seawater as an agent to activate biochar produced from sewage sludge.In our proof-of-concept study,seawater was proven to be an effective activation agent for biochar production,achieving a surface area of 480.3 m^(2)/g with hierarchical porosity distribution.Benefited from our design,the catalytic effect of seawater increased not only the surface area but also the graphitization degree of biochar when comparing the pyrolysis of sewage sludge without seawater.This leads to seawater activated biochar electrodes with lower resistance,higher capacitance of 113.9 F/g comparing with control groups without seawater.Leveraging the global increase in the salinity of groundwater,especially in coastal areas,these findings provide an opportunity for recovering a valuable carbon resource from sludge.

In situ coagulation-electrochemical oxidation of leachate concentrate:A key role of cathodes

To efficiently remove organic and inorganic pollutants from leachate concentrate,an in situ coagulation-electrochemical oxidation(CO-EO)system was proposed using Ti/Ti_(4)O_(7)anode and Al cathode,coupling the“super-Faradaic”dissolution of Al.The system was evaluated in terms of the removal efficiencies of organics,nutrients,and metals,and the underlying cathodic mechanisms were investigated compared with the Ti/RuO_(2)-IrO_(2)and graphite cathode systems.After a 3-h treatment,the Al-cathode system removed 89.0%of COD and 36.3%of total nitrogen(TN).The TN removal was primarily ascribed to the oxidation of both ammonia and organic-N to N_(2).In comparison,the Al-cathode system achieved 3-10-fold total phosphorus(TP)(62.6%)and metal removals(>80%)than Ti/RuO_(2)-IrO_(2)and graphite systems.The increased removals of TP and metals were ascribed to the in situ coagulation of Al(OH)_(3),hydroxide precipitation,and electrodeposition.With the reduced scaling on the Al cathode surface,the formation of Al^(3+)and electrified Al(OH)_(3)lessened the requirement for cathode cleaning and increased the bulk conductivity,resulting in increased instantaneous current production(38.9%)and operating cost efficiencies(48.3 kWh kg_(COD)^(−1)).The present study indicated that the in situ CO-EO process could be potentially used for treating persistent wastewater containing high levels of organic and inorganic ions.

Evaluation of the relationship between two different methods for enumeration fecal indicator bacteria: Colony-forming unit and most probable number

Most probable number （MPN） and colony-forming unit （CFU） estimates of fecal indicator bacteria （FIB） concentration are common measures of water quality in aquatic environments. Thus, FIB intensively monitored in Yeongsan Watershed in an attempt to compare two different methods and to develop a statistical model to convert from CFU to MPN estimates or vice versa. As a result, the significant difference was found in the MPN and CFU estimates. The enumerated Escherichia coli concentrations in MPN are greater than those in CFU, except for the measurement in winter. Especially in fall, E. coli concentrations in MPN are one order of magnitude greater than that in CFU. Contrarily, enterococci bacteria in MPN are lower than those in CFU. However, in general, a strongly positive relationship are found between MPN and CFU estimates. Therefore, the statistical models were developed, and showed the reasonable converting FIB concentrations from CFU estimates to MPN estimates. We expect this study will provide preliminary information towards future research on whether different analysis methods may result in different water quality standard violation frequencies for the same water sample.