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Plastic usage increases year by year, and the growing trend is projected to continue. However as of 2017, only 9% of the 9 billion tons of plastic ever produced had been recycled leaving large amounts of plastics to contaminate the environment, resulting in important negative health and economic impacts. Curbing this trend is a major challenge that requires urgent and multifaceted action. Based on scientific and gray literature mainly published during the last 10 years, this review summarizes key solutions currently in use globally that have the potential to address at scale the plastic and microplastic contaminations from source to sea. They include technologies to control plastics in solid wastes (i.e. mechanical and chemical plastic recycling or incineration), in-stream (i.e. booms and clean-up boats, trash racks, and sea bins), and microplastics (i.e. stormwater, municipal wastewater and drinking water treatment), as well as general policy measures (i.e. measures to support the informal sector, bans, enforcement of levies, voluntary measures, extended producer responsibility, measures to enhance recycling and guidelines, standards and protocols to guide activities and interventions) to reduce use, reuse, and recycle plastics and microplastics in support of the technological options. The review discusses the effectiveness, capital expenditure, and operation and maintenance costs of the different technologies, the cost of implementation of policy measures, and the suitability of each solution under various conditions. This guidance is expected to help policymakers and practitioners address, in a sustainable and cost-efficient way, the plastic and microplastic management problem using technologies and policy instruments suitable in their local context.

In water conservancy projects, automatic grabbing beams, as an important supporting equipment of mobile hoisting equipment, are widely used to improve the performance of operating gates and trash racks. This paper takes the hydraulic automatic grabbing beam of the 2 × 250kN large-span hoist at Baihetan Hydropower Station as an example. The design of the hydraulic automatic grabbing beam for the hoist is systematically analyzed, combined with engineering examples, and the most unfavorable conditions are used. As a result of the calculation, some design parameters of the long-span grab beam were obtained. The test results show that all performance indicators can meet the design requirements and relevant standard requirements.

Singkarak hydro power plant (SHPP) with the capacity of 175 MW provide essential supply to Sumatera Interconnection System thus reliable and efficient operation of the hydro power plant component must be maintained. With the damaged experienced by the trash rack during Padang earthquake, the operation of the power plant was disturbed and replacement of trash rack need to be executed. This study evaluate the modification of trash rack replacement in terms of head loss, potential energy and revenue losses. This simple evaluation finds that the replacement design gives lower head loss which translated to lower energy and revenue losses. The potential energy and revenue losses also increase exponentially with the increase of trash rack blockage. This result amplify the importance of trash rack design and cleaning during operation of a hydro power plant.

Trash racks are extensively used to prevent debris from being transported to down-stream reaches of waterways. However, debris accumulation at the screens can significantly affect their hydraulic performance, resulting in negative economic and environmental consequences. Basic research related to the mechanism of these physical processes is still rather limited. In this experimental study, the flow fields, including the turbulence intensities, Reynolds stresses, and turbulent kinetic energy near a trash rack in a fixed-bed open channel for subcritical flow conditions are investigated for two Reynolds numbers and two blockage ratios. The experimental study investigates the important physical mechanisms relating to turbulence generation and possible sediment deposition induced by the vertical trash rack. Reynolds number effect on time mean streamwise velocity is predominant in the trash rack’s downstream free surface layer as a higher Reynolds number flow has higher normalized streamwise velocity in the free surface layer and lower in the inner layer. In both the Reynolds number effect case and the blockage ratio effect case peak normalized turbulent kinetic energy was observed immediately downstream of the trash rack and with the increment of longitudinal distance downstream of the trash rack, normalized Turbulent kinetic energy is decreased.

All of Badung River with a wide width of 10-40 meters is a typical urban river that has very important meaning to the flood handling system in the Denpasar City area. The results showed that the buildings on the Badung River included 2 trash racks, 1 rubber dam, 2 movable weirs and a 42 km long river wall with an average height of 3-5 m. The flood handling system has been carried out with control of the existing discharge through motion weirs and rubber weirs. While reducing waste that can cause flooding is done by building garbage filters. From the results of the analysis the operating and maintenance costs indicate the cost of routine inspection of 57,772,800 IDR/year, routine search fees of 27,936,000 IDR/year, additional eviction fees of 100,550,400 IDR/year, monitoring and evaluation costs 27,360,000 IDR/year, flood material costs 7,240,000 IDR/year, routine operations and maintenance of 3,306,067,750 IDR/years, the need for periodic fees every 5 years is 2,200,000,000 IDR and the cost of dredging sediments and river stone repairs amounting to 1,113,566,000 IDR every five years.

A new model - super-resolution Wasserstein Generative Adversarial Network with Gradient Penalty (SRWgan-GP) - is developed with resolution of 512×512 to reconstruct the sliced 2D high-resolution flow field from low-resolution data. To train the SRWgan-GP model, flow field data obtained from Large Eddy Simulation (LES) behind the trash racks is utilized. A sub-pixel convolution layer is incorporated in the framework to generate higher-resolution feature maps (512 × 512), which significantly reduces the network's memory requirements under the same output resolution .The performance of the proposed model is compared with that of other commonly used generative models including u-shaped architecture model (Unet) and Convolutional Neural Network (CNN). The results reveal that the SRWgan-GP model excels in reconstructing the flow field along both the x with and y axes, demonstrating the most accurate performance with minimal error achieving an MSE of 0.001, PSNR of 46.557, and SSIM of 0.994 in depicting turbulent structures and the Kįrmįn vortex street. Power Spectral Density (PSD) analysis shows that the primary shedding frequency of the vortex street is consistent with LES at approximately 10Hz for SRWgan-GP. Additionally, the SRWgan-GP exhibits proficient accuracy in computing second-order statistics of the flow field, achieving minimal error in instantaneous Reynolds shear stresses.

Rack clogging can produce dramatic changes in channel hydraulics. Previous studies have investigated the hydraulics of trash racks for various parameters, but the methodology and the findings were not sufficiently refined. Free-surface depression has also been neglected so far. This study considers the rack blockages as impermeable and box-shaped accumulations (instead of considering their bar thicknesses or spacings) for the hydraulic conditions. Hence, flume experiments were performed to clarify the impact of the governing variables on the rack head loss and to examine the characteristics of free-surface depression (i.e. the length of free-surface depression and maximum depth of the depression) because of predefined blockage ratios. The results prove that the rack head loss and flow turbulence behind the rack mainly depend on the rack blockage and Froude number. However, the results for the blockage ratio ≤0.13 at the approach Froude number ≤0.12 has a minor effect on the resulting rack head loss; therefore, the effects are negligible. This study proposed design equations that determine the rack head loss, length of free-surface depression, and maximum depth of the depression behind the rack because of the box-shaped accumulation body that could be used by water engineers. Furthermore, the study improves upon the process understanding of rack blockages to avoid the potential hazards of open channel infrastructure.

This pilot study investigated the amounts of plastic litter captured by water structures. It is based on hydraulic experiments using flume models of the sluice gate and trash racks. Plastic elements of different shapes and sizes were introduced to the flume upstream of the water device. The study measured the number of plastic elements captured by the device. The outcomes of the study suggest that for each device, it should be possible to determine the size of elements beyond which they can capture plastic elements in substantial quantities. The findings should be helpful in designing future experiments on the capture of plastic elements by water structures

Alternative energy sources have a number of advantages over energy derived from fossil and nuclear power plants. In this way, the environment is protected, and many countries are encouraging the use of alternative energy sources. Large potential from this aspect has small hydropower plants, which are not expensive, they can be installed on small rivers, and in this way the received electricity is much cheaper. One of the problems that need to be solved is to prevent the penetration of impurities into turbine plants. This is solved by placing protective trash rack on water intakes. The paper presents an innovative solution for horizontal fine trash-rack with cleaning function for small hydro-electric power stations.

After some 30-40 years of uninterrupted operation, important hydraulic works are in serious need for rehab or retrofit interventions. Works of this type can be made difficult or even prevented by various unforeseen situations, unknown to the specialists because they were not previously accompanied by events that affected neither the operation of the hydraulic systems nor the safety of the constructions and installations. The paper presents the experience of a group of specialists and the way in which the aforementioned unforeseen problems were solved during the rehabilitation works of the bottom outlets of a large dam in Romania. Poiana Uzului dam is the highest buttress dam in Romania (80 m max. height, commissioned in 1972), creating a multipurpose storage reservoir of circa 88 hm3 used for water supply for population and industry, hydroelectricity and flood protection. According to the national dam safety norms, the dam is ranked into the 1st class of importance, which corresponds to a design discharge value of Q0.1% (maximum discharge value with an annual exceedance probability of 0.1%). According to the Romanian design standard STAS 4273-83, for the 1st class of importance, the dam discharge capacity has to be also verified for a much higher value, Q0.01%. The dam was provided with 3 bottom outlets, each equipped with trash racks and 2 \"butterfly\" valves. The advanced wear of the bottom outlets equipment determined malfunctions of the service valves, as well as deterioration of the thrash racks, metal fragments posing serious threat upon the safe operation of the valves and of the outlets. Rehabilitation of the bottom outlets equipment was not possible with the complete emptying of the reservoir since it represents the only source of water for a number of circa 150,000 inhabitants in about 7 localities in the neighbouring areas. However, the intervention was possible with partial emptying of the reservoir, using professional divers to perform repair works in very difficult conditions. The lower limit to which the reservoir was emptied was conditioned by a program of monitoring the water quality parameters, allowing the uninterrupted supply of water for population consumption.