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Proper control of phytosterols in pulp mill effluents is necessary before disposal into receiving environments because they have been suspected to be hormonally active to aquatic life. This study provides an insight into the adsorptive behavior of sterols and the role of secondary sludge in their removal during secondary treatment. The kinetics of sterol adsorption, extent of sterol adsorption onto inactivated secondary solids, adsorptive capacity of secondary solids, and the relative contribution of the adsorption mechanism in the overall removal of sterols during secondary treatment have been investigated in this study. Isotherm modeling revealed two different adsorption regimes for each sterol. The results show that adsorption plays a major role in the secondary treatment of pulp mill effluents and that secondary sludge serves as an efficient adsorbent to remove phytosterols. The obtained information is important to improve system design and optimize the operation of pulp mill effluent treatment facilities. [ABSTRACT FROM AUTHOR]

The Dujiangyan Project is a World Cultural Heritage Site with relevance to water conservancy. It has been operated for more than 2,260 years and still plays an important role in irrigation, urban, and industrial water supply, flood control, and tourism. This paper discusses the hydraulic principles of the project, focusing on the reasons for the longevity of the project. In particular, two aspects of the project are reviewed; namely, the practical engineering design of the project and its outstanding historical significance and time-based maintenance. The project ingeniously used the topography of the terrain in the design of weir structures. The tasks of water diversion, irrigation, and flood control were achieved using a two-step approach. The first step was achieved by utilizing the shifting of streamlines and the bend of flow from the town of Guankou to Fish Mouth (a diversion embankment). The discharge of flow and sediment was further optimized by using the second step of combined control of Feishayan (a sediment and flow spillway) and Baopingkou (an irrigating gate). The bend of flow within the Inner River forces the surface water to flow into Baopingkou, whereas the bottom sediments and pebbles discharge from Feishayan. Dynasties throughout history attached great importance to the management and maintenance of the project. Retrofitting and time-based renovation prevented the abandonment of the project due to sediment accumulation and aging of building materials. Because the maintenance and operation costs were far lower than the economic, social, and ecological benefits the project had brought, the Dujiangyan Project was sustainable over the long term. The study of the engineering design and maintenance rules of the Dujiangyan Project has value for the design and construction of modern hydraulic projects. [ABSTRACT FROM AUTHOR]

The Government of Canada has endorsed a policy to promote water conservation in an attempt to reduce environmental impacts of water use. Nonetheless, total water intake, consumption, and gross water use in the business sector have increased in the period 1981–1996. Water intake intensities, measured in cubic meters of intake water per dollar of production, however, have fallen by 4%. To better understand these changes in intensities, we decompose them into separate composition and technique effects. We show that changes in the composition of business activity have lead to an expansion of water intensive industries. However, changes in techniques and production processes have more than offset this. Overall, water intake intensities have fallen by 7%, after accounting for changes in the relative growth of sectors. These reductions are even stronger when we include recirculated water where technological and process changes have reduced gross water intensities by 18%. At the same time, though, firms have increased their consumption of water so that, on average, consumption intensities rose 17%. Hence, firm level changes in techniques and processes may have increased the impact of economic activity on the environment rather than having reduced it. [ABSTRACT FROM AUTHOR]

This study investigated the applicability of maghemite (γ-Fe2O3) nanoparticles for the selective removal of toxic heavy metals from electroplating wastewater. The maghemite nanoparticles of 10 nm were synthesized using a sol–gel method and characterized by X-ray diffraction (XRD) and transmission electron microscopy (TEM). The surface area of the nanoparticles was determined to be 198 m2/g using the Brunauer–Emmett–Teller method. Batch experiments were carried out to determine the adsorption kinetics and mechanisms of Cr(VI), Cu(II), and Ni(II) by maghemite nanoparticles. The adsorption process was found to be highly pH dependent, which made the nanoparticles selectively adsorb these three metals from wastewater. The adsorption of heavy metals reached equilibrium rapidly within 10 min and the adsorption data were well fitted with the Langmuir isotherm. Regeneration studies indicated that the maghemite nanoparticles undergoing successive adsorption–desorption processes retained original metal removal capacity. Mechanism studies using TEM, XRD, and X-ray photoelectron spectroscopy suggested that the adsorption of Cr(VI) and Cu(II) could be due to electrostatic attraction and ion exchange, and the adsorption of Ni(II) could be as a result of electrostatic attraction only. [ABSTRACT FROM AUTHOR]

A market-based water supply problem is modeled as an optimization problem maximizing net benefit from water use such that all the concerned parties use an economically optimal allocation considering damages due to total dissolved solids (TDS) and institutional constraints. These institutional constraints include water supply requirements under international treaty and historical allocations of water to agriculture. The income from water in municipal use, based on the concept of consumer surplus, is utilized in the objective function along with benefit from agricultural uses, supply costs, and damage costs due to poor quality water, which are estimated using available data. The research assesses the impact that system-wide optimal allocation of water will have in increasing monetary benefits and reducing water salinity levels in terms of TDS along the reach of the Rio Grande from Elephant Butte, New Mexico, to Fort Quitman, Texas. The analysis is performed under three institutional constraints, which include flow regulation at the reservoir, restrictions on trade between states, and allowing trade between the states. Among these scenarios, allowing trade between the states results in the best solution in terms of both net benefit and reducing damage due to poor quality water. [ABSTRACT FROM AUTHOR]