Teleseismic waves reveal anisotropic poroelastic response of wastewater disposal reservoir

Connecting earthquake nucleation in basement rock to fluid injection in basal,sedimentary reservoirs,depends heavily on choices related to the poroelastic properties of the fluid-rock system,thermo-chemical effects notwithstanding.Direct constraints on these parameters outside of laboratory settings are rare,and it is commonly assumed that the rock layers are isotropic.With the Arbuckle wastewater disposal reservoir in Osage County,Oklahoma,high-frequency formation pressure changes and collocated broadband ground velocities measured during the passing of large teleseismic waves show a poroelastic response of the reservoir that is both azimuthally variable and anisotropic;this includes evidence of static shifts in pressure that presumably relate to changes in local permeability.The azimuthal dependence in both the static response and shear coupling appears related to tectonic stress and strain indicators such as the orientations of the maximum horizontal stress and faults and fractures.Using dynamic strains from a nearby borehole strainmeter,we show that the ratio of shear to volumetric strain coupling is~0.41 which implies a mean Skempton's coefficient of A=0.24 over the plausible range of the undrained Poisson's ratio.Since these observations are made at relatively low confining pressure and differential stress,we suggest that the hydraulically conductive fracture network is a primary control on the coupling between pore pressure diffusion and elastic stresses in response to natural or anthropogenic sources.

Photothermal-photocatalytic thin-layer flow system for synergistic treatment of wastewater

The integration of the photocatalytic effect into solar steam is highly desirable for addressing freshwater shortages and water pollution.Here,a ternary film structure for the adsorption and photothermal and photocatalytic treatment of wastewater was designed by combining the technique of self-assembled carbon nano paper with a nitrogen composite titanium dioxide(N-TiO_(2))deposited on the surface of carbon nanotubes(CNT)using polyvinylidene fluoride(PVDF)as a substrate.The photogeneration of reactive oxygen species can be promoted by rapid oxygen diffusion at the three-phase interface,whereas the interfacial photothermal effect promotes subsequent free radical reactions for the degradation of rhodamine B(93%).The freshwater evaporation rate is 1.35 kg·m^(-2)·h^(-1)and the solar-to-water evaporation efficiency is 94%.Importantly,the N-TiO_(2)/CNT/PVDF(N-TCP)film not only effectively resists mechanical damage from the environment and maintains structural integrity,but can also be made into a large film for outdoor experiments in a large solar energy conversion device to collect fresh water from polluted water and degrade organic dyes in source water simultaneously,opening the way for applications in energy conversion and storage.

Application of Liquid Solid Semi-moving Bed to Fractionation of Cesium Ion in Wastewater

A liquid solid semi-moving bed with non-mechanical particle transport system is proposed and used for fractionation of cesium ion in wastewater. The particle transport system, which consists of a suction chamber, a mixing chamber, a nozzle and a riser tube, is designed to be controlled completely by hydraulic force. Experiments show that continuous feeding and discharging of resin can be realized by the transport system. The removal of cesium ion from wastewater is realized, The concentration of cesium ion in effluent liquid remains below 0,1g·L^-1 （the initial concentration is 5,3g·L^-1） during the 73 hours＇ experiment. The average exchange capacity of resin discharged from the bed is 0.57mmol,（g dry resin）^-1, which is close to the saturated capacity of 0.65mmol·g^-1. And it is also proved that the non-homogeneity of particle vertical velocity along the radial direction can seriously influence the ion-exchange process.

Growing seismicity in the Sichuan Basin and its association with industrial activities

In the Sichuan Basin,seismic activity has been low historically,but in the past few decades,a series of moderate to strong earthquakes have occurred.Especially since 2015,earthquake activity has seen an unprecedented continuous growth trend,and the magnitude of events is increasing.Following the M5.7 Xingwen earthquake on 18 Dec.2018,which was suggested to be induced by shale gas hydraulic fracturing,a swarm of earthquakes with a maximum magnitude up to M6.0 struck Changning and the surrounding counties.Questions arose about the possible involvement of industrial actions in these destructive events.In fact,underground fluid injection in salt mine fields has been occurring in the Sichuan Basin for more than70 years.Disposal of wastewater in natural gas fields has also continued for about 40 years.Since 2008,injection for shale gas development in the southern Sichuan Basin has increased rapidly.The possible link between the increasing seismicity and increasing injection activity is an important issue.Although surrounded by seismically active zones to the southwest and northwest,the Sichuan Basin is a rather stable region with a wide range of geological settings.First,we present a brief review of earthquakes of magnitude 5 or higher since 1600 to obtain the long-term event rate and explore the possible link between the rapidly increasing trend of seismic activity and industrial injection activities in recent decades.Second,based on a review of previous research results,combined with the latest data,we describe a comprehensive analysis of the characteristics and occurrence conditions of natural and injection-induced major seismic clusters in the Sichuan Basin since 1700.Finally,we list some conclusions and insights,which provide a better understanding of why damaging events occur so that they can either be avoided or mitigated,point out scientific questions that need urgent research,and propose a general framework based on geomechanics for assessment and management of earthquake-related risks.

Quantifying and managing regional greenhouse gas emissions: Waste sector of Daejeon, Korea

A credible accounting of national and regional inventories for the greenhouse gas （GHG） reduction has emerged as one of the most significant current discussions. This article assessed the regional GHG emissions by three categories of the waste sector in Daejeon Metropolitan City （DMC）, Korea, examined the potential for DMC to reduce GHG emission, and discussed the methodology modified from Intergovernmental Panel on Climate Change and Korea national guidelines. During the last five years, DMC＇s overall GHG emissions were 239 thousand tons C02 eq./year from eleven public environmental infrastructure facilities, with a population of 1.52 million. Of the three categories, solid waste treatment/disposal contributes 68%, whilst wastewater treatment and others contribute 22% and 10% respectively. Among GHG unit emissions per ton of waste treatment, the biggest contributor was waste incineration of 694 kg CO2 eq./ton, followed by waste disposal of 483 kg CO2 eq./ton, biological treatment of solid waste of 209 kg CO2 eq./ton, wastewater treatment of 0.241 kg CO2 eq./m3, and public water supplies of 0.067 kg CO2 eq./m3. Furthermore, it is suggested that the potential in reducing GHG emissions from landfill process can be as high as 47.5% by increasing landfill gas recovery up to 50%. Therefore, it is apparent that reduction strategies for the main contributors of GHG emissions should take precedence over minor contributors and lead to the best practice for managing GHGs abatement.