Aim Factors affecting faecal indicator bacteria (FIB) and pathogen survival/persistence in sand remain largely unstudied. This work elucidates how biological and physical factors affect die-off in beach sand following sewage spills. Methods and Results Solar disinfection with mechanical mixing was pilot-tested as a disinfection procedure after a large sewage spill in Los Angeles. Effects of solar exposure, mechanical mixing, predation and/or competition, season, and moisture were tested at bench scale. First-order decay constants for Escherichia coli ranged between −0·23 and −·102 per day, and for enterococci between −0·5 and −1·0 per day. Desiccation was a dominant factor for E. coli but not enterococci inactivation. Effects of season were investigated through a comparison of experimental results from winter, spring, and fall. Conclusions Moisture was the dominant factor controlling E. coli inactivation kinetics. Initial microbial community and sand temperature were also important factors. Mechanical mixing, common in beach grooming, did not consistently reduce bacterial levels. Significance and Impact of the Study Inactivation rates are mainly dependent on moisture and high sand temperature. Chlorination was an effective disinfection treatment in sand microcosms inoculated with raw influent.

In western North America, massive infrastructure systems convey water over hundreds of miles to support cities, farms and economic growth. The systems were twentieth-century solutions to seasonal water scarcity, but today imported water supplies are strained. Cities are looking to water conservation and local sources of supply as future solutions. But integrated planning remains a challenge. Here, we assess economic implications of transitioning to local water supply reliance. We enhance an integrated model (Artes) of urban water management in Los Angeles County (LA County) with annualized costs for water supply sources (local and imported) and water conservation. We model cost-effective options for mitigating the effects of imported water cuts affecting nine million people within a hundred agencies, and denote associated policy options. The approach allows for a more holistic assessment that improves upon current studies, which typically compare nominal and annualized prices of different options. The concept of urban water supply trains, which include the multiple steps of acquiring, treating, distributing, and discharging or reusing water, is presented to understand emerging cycles of water supply. The analysis enhances current studies that often emphasize single agency perspectives, but also shows how existing assumptions and infrastructure shape what appear to be cost-effective options.Systematic studies of urban water management necessarily include many aspects of operations [1][2][3][4] . Engineered pipe and channel networks move surface water and runoff. Water supply utilities build and maintain systems to keep taps running. Complex networks of agencies oversee the acquisition, distribution and use of urban water and wastewater 5,6 . Landscapes and outdoor water use are especially important drivers of water demand in California, as half of urban water use goes to irrigation and trees [7][8][9][10] . Economics and social attitudes shape the expectations of residents and utilities for water supply. In many cities across the globe, climate change and population growth will test operating assumptions in the current systems 11 .Los Angeles County is an immense laboratory for exploring the future of urban water in seasonally dry climates (Fig. 1). The county currently receives 55-60% of its annual water supplies from imported sources, which include northern California through the Sacramento-San Joaquin Delta, the Colorado River basin, and the higher-altitude Owens Valley. The remainder comes from local sources, including groundwater pumping, recycled water (nonpotable or indirect recharge) and stormwater capture 5,12,13 . Of the water imported to southern California by the giant Metropolitan Water District of Southern California (MWD), Los Angeles County agencies receive approximately 40%. The City of Los Angeles receives additional imports from the Owens Valley. A shift to becoming primarily reliant on local sources is significant in a region famous for its efforts to import water [14][15][16] .Previously, to u...

Los Angeles, which relies on large infrastructure systems that import water over hundreds of miles, faces a future of reduced imports. Within Los Angeles and its hundreds of water agencies, the capacity to adapt to future changes is influenced by laws, institutions, and hydrogeology. This paper presents a systems analysis of urban water management in metropolitan Los Angeles County to assess opportunities for increasing local water reliance. A network flow model was developed to investigate management tradeoffs across engineered, social, and environmental systems. With an aggressive regional demand target, increased stormwater capture (300%), and prioritized water reuse from existing facilities, imported water supplies can be cut by 30% while maintaining landscapes, economic productivity, and groundwater resources. Further reducing imports (by 40-50%) is possible through actions to promote additional reuse, recharge, conservation, and groundwater access. Reducing imported water without significant conservation results in likely groundwater overdraft. Fragmented networks of agencies in Los Angeles create an uneven landscape of vulnerability to water shortages. The paper discusses model applications, research needs, and policy implications of results for dry-climate cities.

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The LEGaTO project leverages task-based programming models to provide a software ecosystem for Made in-Europe heterogeneous hardware composed of CPUs, GPUs, FPGAs and dataflow engines. The aim is to attain one order of magnitude energy savings from the edge to the converged cloud/HPC, balanced with the security and resilience challenges. LEGaTO is an ongoing three-year EU H2020 project started in December 2017.

Acute water shortages for large metropolitan regions are likely to become more frequent as climate changes impact historic precipitation levels and urban population grows. California and Los Angeles County have just experienced a severe four year drought followed by a year of high precipitation, and likely drought conditions again in Southern California. We show how the embedded preferences for distant sources, and their local manifestations, have created and/or exacerbated fluctuations in local water availability and suboptimal management. As a socio technical system, water management in the Los Angeles metropolitan region has created a kind of scarcity lock-in in years of low rainfall. We come to this through a decade of coupled research examining landscapes and water use, the development of the complex institutional water management infrastructure, hydrology and a systems network model. Such integrated research is a model for other regions to unpack and understand the actual water resources of a metropolitan region, how it is managed and potential ability to become more water self reliant if the institutions collaborate and manage the resource both parsimoniously, but also in an integrated and conjunctive manner. The Los Angeles County metropolitan region, we find, could transition to a nearly water self sufficient system. Keywords Water scarcity • Socio-technical systems • Integrated water management • Water self-reliance

Reducing energy consumption for urban water management may yield economic and environmental benefits. Few studies provide comprehensive assessments of energy needs for urban water sectors that include both utility operations and household use. Here, we evaluate the energy needs for urban water management in metropolitan Los Angeles (LA) County. Using planning scenarios that include both water conservation and alternative supply options, we estimate energy requirements of water imports, groundwater pumping, distribution in pipes, water and wastewater treatment, and residential water heating across more than one hundred regional water agencies covering over 9 million people. Results show that combining water conservation with alternative local supplies such as stormwater capture and water reuse (nonpotable or indirect potable) can reduce the energy consumption and intensity of water management in LA. Further advanced water treatment for direct potable reuse could increase energy needs. In aggregate, water heating represents a major source of regional energy consumption. The heating factor associated with grid-supplied electricity drives the relative contribution of energyfor-water by utilities and households. For most scenarios of grid operations, energy for household water heating significantly outweighs utility energy consumption. The study demonstrates how publicly available and detailed data for energy and water use supports sustainability planning. The method is applicable to cities everywhere.

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