Hasil untuk "Environmental technology. Sanitary engineering"

Martin Bellmann, Berhane Darsene Dimd, Anne‐Karin Søiland et al.

In the ICARUS project, European partners collaborate to develop and scale innovative technologies for recovering and refining secondary raw materials from silicon photovoltaic (PV) manufacturing. The production of photovoltaic modules generates significant quantities of waste, particularly silicon kerf, graphite, and silica residues from ingot and wafer manufacturing. ICARUS aims to transform these waste streams into high‐value secondary materials suitable for reintegration into the PV value chain and other industrial applications. Four industrial pilot‐scale processes are developed, targeting the purification and reuse of these materials. Results from the pilots demonstrate both the technical feasibility and economic potential of substituting these recovered materials for virgin and critical raw materials. This work provides a viable pathway toward a more resource‐efficient and circular PV manufacturing industry.

Hao Li, Yongkang Qi, Minru Su et al.

Electrodes with high activation efficiency and stability are critical for the electrochemical activation of persulfate. In this study, the effective degradation of acid orange 74 (AO 74) was achieved using the electrochemically activated peroxydisulfate (PDS) with a Ag nanoparticle–modified carbon paper (AgNPs@CP) electrode, demonstrating a 2.5-fold enhancement in the AO 74 degradation rate compared with the CP electrode. The impact of reaction conditions, including AgNPs dosage, PDS content, current density, initial solution pH, and agitation rate, as well as water matrices, such as Cl−, CO32−, and SO42−, on AO 74 degradation was systematically investigated to establish optimal parameters. Radical quenching experiments and electron paramagnetic resonance analysis identified sulfate radical and hydroxyl radical as the dominant reactive species. Gas chromatography–mass spectrometry analysis revealed that AO 74 was primarily transformed into aliphatic organic compounds during electrochemical degradation. Remarkably, the 3-h AO 74 degradation efficiency remained stable over five consecutive cycles through alternating use of the AgNPs@CP anode and CP cathode, facilitated by Ag0/Ag+/Ag2+ redox cycling that enabled Ag recovery and minimized Ag leaching. The electrochemically activated PDS with the AgNPs@CP electrode shows promise as a pretreatment technology for dyeing wastewater with low biodegradability.

Divya Nimma, Okram Ricky Devi, Bibek Laishram et al.

Global warming is a phenomenon whereby the planet's exposure to the sun's radiation worsens from the high emission of gasses believed to trap heat within the atmosphere. Carbon dioxide (CO2) is the leading greenhouse gas majorly responsible for global warming and other related issues and is a danger to global society. This one has a particular role in portraying the key importance of the shifting climate that invariably influences water supply and agricultural production. Global warming presents complex challenges to aquatic organisms and stocks and other natural aquatic life resources. This study examines how freshwater and marine species are affected by climate change in aquatic habitats. Aquatic species' metabolism, growth, reproduction, and dispersal are all impacted by rising temperatures and altered water chemistry brought on by increased greenhouse gas emissions, especially CO2. The goal is to pinpoint the ecosystems and vulnerable species that are most impacted by these changes and suggest flexible management techniques. The suggested remedies center on creating sustainable conservation strategies that lessen the effects of climate change on aquatic biodiversity and increase these ecosystems' resilience. The socio-economic interdependencies between water and climate change impact agricultural and water resources, and the pressures exerted on water bodies and water supply landscapes. Another area is related to alterations in the physical and chemical properties of the water, such as the temperature, which is a well-known effect of climate change: 'This causes abnormalities in the metabolism and physiology of aquatic species.' These alterations flow through the chain and regime of growth, reproduction, feeding habits and distribution, migration, and mass of fish and other creatures in the water system. However, the long-term effect of climate variation and climate change on freshwater ecosystems requires much scientific investigation to address challenges in aquatic ecosystem conservation and sustainability. This being the case, adaptive management solutions that address the interrelated impacts of climate change have to be applied and implemented to reduce vulnerability in aquatic ecosystems worldwide.

Zhineng Liu, Xiaolan Lao, Dongjing Zhou et al.

Pesticides are essential for crop protection and agricultural yield enhancement. However, their entry into water bodies, particularly drinking water sources, poses threats to human health and aquatic ecosystems. The seasonal variation, and potential risks of pesticides in drinking water sources in Guangdong, China were investigated. The total pesticide concentrations were significantly elevated during the dry season compared to the wet season (p < 0.01; |r| = 0.77; 95 % CI for difference in medians: [92.6, 315] ng/L). Neonicotinoid pesticides predominated in more than half of the samples. Across both seasons, river water sources displayed significantly higher total pesticide concentrations than reservoir sources (dry season: p < 0.05, |r| =0.60, 95 % CI [106,359] ng/L; wet season: p < 0.01, |r| =0.66, 95 % CI [70.3, 412] ng/L). Health risk assessments indicated that pesticides in drinking water sources pose non-carcinogenic and carcinogenic risks associated with long-term direct consumption, particularly for children aged 3–4 years. Ecological risk assessments revealed high potential risks to aquatic organisms (summed risk quotient > 1), particularly from neonicotinoid pesticides. These findings highlight the necessity of seasonally adaptive controls for pesticides and water quality to reduce risks to public health and ecosystems.

Tesfaye Bayu Zeleke, Tri Retnaningsih Soeprobowati, Solomon Adissu et al.

The trends of temperature and rainfall are critical indicators of climate change within a certain area. However, the existence of climate change is not locally understood in most parts of the world. This research aims to analyze the trend of temperature and rainfall in the Lake Tana Sub-basin as a means to understand the current and future status of climate change. The trends of temperature and rainfall were analyzed using the modified Mann-Kendall trend test, while the autoregressive integrated moving average model (ARIMA) was used to predict future temperature and rainfall. The findings reveal that monthly temperatures show a significant increasing trend for March, April, May, June, and December with Z-values of 3.96, 3.32, 2.64, 3.21, and 4.6, respectively. Seasonal and annual temperatures also show a significant increasing trend with Z-values of 4, 5.35, 5.08, and 4.41 for spring, autumn, winter, and annual, respectively. The Mann-Kendall trend analysis results show that monthly, seasonal and annual rainfall exhibit significant increasing trends for some months and seasons. The results of the ARIMA model suggest that the predicted values of temperature and rainfall will continue to increase over the next 10 years in the study area. Based on these findings, it can be concluded that there is a significant and increasing trend in temperature and rainfall, which will likely continue over the next decade, indicating the presence of climate change in the study area. The research findings suggest that temperature and rainfall have been increasing over time, leading to climate change in the study area, so sustainable lake management and urban development should be practiced to mitigate and adopt climate change.

Nils R. B. Olsen, Subhojit Kadia, Elena Pummer et al.

A new OpenFOAM solver has been developed for computing the spatial variation of particle concentrations in flowing water. The new solver was programmed in C ++ using OpenFOAM libraries, and the source code has been made openly available. The current article describes the coding of how the water flow and particle movements are computed. The solver is based on a Eulearian approach, where the particles are computed as concentrations in cells of a grid that resolves the computational domain. The Reynolds-averaged Navier–Stokes equations are solved by simpleFoam, using the k-ε turbulence model. The new solver uses a drift-flux approach to take the fall or rise velocity of the particles into account in a convection-diffusion equation. The model is therefore called sediDriftFoam. The results from the solver were tested on two cases with different types of particles. The first case was a sand trap with sand particles. The geometry was three-dimensional with a recirculation zone. The computed sediment concentrations in three vertical profiles compared well with earlier numerical studies and laboratory measurements. The second case was a straight channel flume with plastic particles that had a positive rise velocity. In this case, the results also compared well with the laboratory measurements. HIGHLIGHTS Open source 3D sediment model.; Based on OpenFOAM.; Simple and easy to learn.; Tested on computing trap efficiency of a sand trap.; Tested on computing suspended plastic particles in a channel.;

Zhou Wang, Ru Huang, Qichao Yao et al.

Accounting for 41.7% of China’s total land area, grasslands are linked to the livelihoods of over 20 million people. Although grassland fires cause severe damage in China every year, their spatiotemporal patterns and climate drivers are not well understood. In this study, we used grassland fire record forms provided by the National Forestry and Grassland Administration and grassland fire location data from the Wildfire Atlas of China to examine the spatiotemporal patterns and and seasonality of fires in China for the period from 2008 to 2020. We found that most grassland fires occurred in Inner Mongolia in northern China, specifically in the Hulun Buir and Xilingol grasslands. We found distinct differences in fire seasonality in northern China, which has a major fire season in April, versus southwestern China, where the major fire season occurs in February, March and April. April grassland fires in northern China are the result of strong winds, typically from the west, and spring drought. A secondary fire season in northern China occurs in October and is also driven by strong winds. The fire season in southwestern China seems to be less shaped by climatic factors such as wind speed, precipitation, and drought. This study provides support for decision-making by fire prevention and fire management authorities in China.

Phaothep Cherdsukjai, Vararin Vongpanich, Pensiri Akkajit

Plastics can reach the coastal environment and could impact the marine environment. Mussels are marine organisms which are prone to be exposed to microplastics pollution. Therefore, in this preliminary study, the commercially important green mussel (Perna viridis) collected at the Koh Phee Canal in Phuket, Phuket Province, southern peninsular Thailand, was investigated. The collected mussels from aquaculture farm fell into three age groups, namely 1 year-1 month, 1 year-7 months, and 1 year-9 months. Results from the investigation showed 200 items of microplastics present in Perna viridis with 76 items (38%) in flushed water and 124 items (62%) in the soft tissue. The average counts of microplastics in soft tissue and flushed water were 4.13 items per individual and 2.53 items per individual, respectively. Blue color (98 items, 49%) and filament shape (185 items, 92.5%) were the most common color and shape of microplastics in the mussel tissues and the flushed water. The dominant polymers as microplastics were identified as polyester and polyethylene terephthalate, which are common polymer types used in protective packaging and containers. The statistical post hoc tests showed no significant differences by age group in the microplastics accumulation in the Perna viridis (p<0.05). Further studies are required to understand the accumulation rates and residence times of microplastics across the food webs for better understanding on their impacts on human health. The results from this study provide a baseline level of microplastics contamination in green mussel aquaculture located at Phuket, and urgent measures are needed to prevent contamination of food for human consumption and related health problems.

A. Khouz, A. Khouz, A. Khouz et al.

<p>In recent decades, multiple researchers have produced landslide susceptibility maps using different techniques and models, including the information value method, which is a statistical model that is widely applied to various coastal environments. This study aimed to evaluate susceptibility to landslides in the Essaouira coastal area using bivariate statistical methods. In this study, 588 distinct landslides were identified, inventoried, and mapped. Landslides are performed by means of observation and interpretation of different data sources, namely high-resolution satellite images, aerial photographs, topographic maps, and extensive field surveys. The rocky coastal system of Essaouira is located in the middle of the Atlantic coast of Morocco. The study area was split into 1534 cliff terrain units that were 50 m in width. For training and validation purposes, the landslide inventory was divided into two independent groups: 70 % for training and 30 % for validation. Twenty-two layers of landslide conditioning factors were prepared – namely, elevation, slope angle, slope aspect, plan curvature, profile curvature, cliff height, topographic wetness index, topographic position index, slope over area ratio, solar radiation, presence of faulting, lithological units, toe lithology, presence and type of cliff toe protection, layer tilt, rainfall, streams, land-use patterns, normalised difference vegetation index, lithological material grain size, and presence of springs. The statistical relationship between the conditioning factors and the different landslide types was calculated using the bivariate information value method in a pixel-based model and in the elementary terrain units-based model. Coastal landside susceptibility maps were validated using landslide training group partitions. The receiver operating characteristic curve and area under the curve were used to assess the accuracy and prediction capacity of the different coastal landslide susceptibility models. Two methodologies, considering a pixel-based approach and using coastal terrain units, were adopted to evaluate coastal landslide susceptibility. The results allowed for the classification of 38 % of the rocky coast subsystem as having high susceptibility to landslides, which were mostly located in the southern part of the Essaouira coastal area. These susceptibility maps will be useful for future planned development activities as well as for environmental protection.</p>

Farnaz Daneshvar Vousoughi

Two approaches were used in the Ardabil Plain to determine the relationship between hydrological time-series (rainfall and runoff) and the groundwater level (GWL). The wavelet-entropy measure (WEM) and the wavelet transform coherence (WTC) were used as two approaches of the wavelet transform (WT). The WEM was considered as a criterion for the degree of fluctuation of the time-series and the WTC represents a common time–frequency space. In the calculation of the WEM, the monthly rainfall, runoff, and the GWL time-series were divided into three different time periods and decomposed into several frequent time-series. Wavelet energies were then calculated for each sub-series. The WEM results show a decrease in rainfall, runoff, and the GWL. The reduction in the WEM represents the reduction in the natural variation of the time-series. The reduction of entropy for runoff, rainfall, and the GWL time-series was about 1.58, 1.36, and 29%, respectively. It can be concluded that the reduction in the fluctuation of the hydrological time-series has relatively little effect on the oscillation patterns of the GWL signal. In this regard, it could be concluded that human activities such as pumping water from wells play a main role in reducing the GWL in the Ardabil Plain. The WTC results show that runoff has the highest coherence (0.9–1) among hydrological variables with the GWL time-series in the frequency bands of 4–8 and 8–16 months. HIGHLIGHTS The wavelet-entropy measure (WEM) as a criterion is used to investigate the effect of hydrological parameters on groundwater level.; Wavelet transform coherence (WTC) is used to determine the frequency relationship between hydrological time-series and the groundwater level.;

Yi Wang, Junfu Chen, Benquan Fu et al.

Abstract The disposal of waste oil, paint and coating barrels (WOPCBs) after use is an ongoing social and environmental problem. In this paper, a novel technological scheme using steel converter co-processing is proposed for the safe disposal and resource utilization of WOPCBs. The scheme is mainly composed of WOPCBs pretreatment and converter disposal, focusing on the impact of converter co-processing WOPCBs on the environment and production process. Compared to the traditional technology, the scheme presented takes full advantages of the production process and environmental protection facilities of steel converter, and has many advantages, such as a large disposal capacity, low cost, highly efficient and environmentally friendly. The industrial trials results show that after adding 180–540 kg WOPCBs to each furnace load (nominal capacity 250 t), the converter operation is safe and controllable, and all the pollutant emission indicators generated in the process meet the Chinese national standards. In addition, WOPCBs are suitable to be used as a supplementary material for scrap steel. Therefore, this study provides important insights for sustainable resource utilization from WOPCBs.

Beata Dąbrowska-Bouta, Grzegorz Sulkowski, Jolanta Orzelska-Górka et al.

The increasing production and use of silver nanoparticles (AgNPs) as antimicrobial agents in medicinal and commercial products creates a substantial risk of exposure, especially for infants and children. Our current knowledge concerning the impact of AgNPs on developing brain is insufficient. Therefore we investigated the temporal profile of transcriptional changes in cellular components of the neurovascular unit in immature rats exposed to a low dose of AgNPs. The behavior of animals under these conditions was also monitored. Significant deposition of AgNPs in brain of exposed rats was identified and found to persist over the post-exposure time. Substantial changes were noted in the transcriptional profile of tight junction proteins such as occludin and claudin-5, and pericyte-related molecules such as angiopoietin-1. Moreover, downregulation of platelet-derived growth factor (PDGFβ) and its receptor (PDGFβR) which constitute the main signaling pathway between endothelial cells and pericytes was observed. These were long-lasting effects, accompanied by overexpression of astroglial-specific GFAP mRNA and endothelial cell adhesion molecule, ICAM-1, involved in the pathomechanism of neuroinflammation. The profile of changes indicates that even low doses of AgNPs administered during the early stage of life induce dysregulation of neurovascular unit constituents which may lead to disintegration of the blood-brain barrier. This was confirmed by ultrastructural analysis that revealed enhanced permeability of cerebral microvessels resulting in perivascular edema. Changes in the behavior of exposed rats indicating pro-depressive and anti-anxiety impacts were also identified. The results show a high risk of using AgNPs in medical and consumer products dedicated for infants and children.

Joel Methorst, Ugo Arbieu, Aletta Bonn et al.

Wildlife has important effects on human well-being, ranging from beneficial contributions to life threatening interactions. Here, we systematically reviewed publications of both positive and negative non-material contributions of wildlife to people (WCP) for different taxonomic groups (birds, mammals, reptiles and amphibians) and dimensions of human well-being such as health, social well-being, identity and spirituality. Overall, the majority of studies reported negative WCP, such as feelings of insecurity or injuries. However, over the last decade the number of publications on positive WCP such as good mental health, positive emotions or learning increased, mainly in the Global North. These spatial and temporal patterns may hint towards normative influences that drive the relative proportion of reported WCP. However, these normative influences are not yet well understood and future research should examine potential biases by conducting policy assessments or surveys among researchers to understand drivers and motivations behind their research questions. We found almost no joint assessments of positive and negative WCP for any wildlife species. Studies also showed taxon-specific differences in WCP outcomes, with predominantly positive WCP reported for birds and predominantly negative WCP published for mammals or reptiles. Physical health was the most dominant aspect of well-being studied and affected by WCP while other well-being dimensions such as social well-being, learning or identity were less frequently covered in the literature. Future studies should jointly evaluate positive and negative effects of wildlife on human well-being and implement multi-taxon approaches to obtain a more balanced and comprehensive understanding of WCP. These assessments of WCP will provide actionable science outcomes that will shape human-wildlife coexistence and promote human health and well-being.

CHAIX, Christophe

Planification et adaptation font-elles bon ménage dans les territoires de moyenne montagne? Pour y répondre, des acteurs franco-italiens ont initié en 2017 le projet européen ARTACLIM. Conçu comme un projet de recherche-action, il a pour objectif de promouvoir l'introduction de mesures d'adaptation au changement climatique dans le cadre de la planification et de l'aménagement du territoire des administrations publiques.

M. Fencl, M. Dohnal, J. Rieckermann et al.

Increasing urbanization makes it more and more important to have accurate stormwater runoff predictions, especially with potentially severe weather and climatic changes on the horizon. Such stormwater predictions in turn require reliable rainfall information. Especially for urban centres, the problem is that the spatial and temporal resolution of rainfall observations should be substantially higher than commonly provided by weather services with their standard rainfall monitoring networks. Commercial microwave links (CMLs) are non-traditional sensors, which have been proposed about a decade ago as a promising solution. CMLs are line-of-sight radio connections widely used by operators of mobile telecommunication networks. They are typically very dense in urban areas and can provide path-integrated rainfall observations at sub-minute resolution. Unfortunately, quantitative precipitation estimates (QPEs) from CMLs are often highly biased due to several epistemic uncertainties, which significantly limit their usability. In this manuscript we therefore suggest a novel method to reduce this bias by adjusting QPEs to existing rain gauges. The method has been specifically designed to produce reliable results even with comparably distant rain gauges or cumulative observations. This eliminates the need to install reference gauges and makes it possible to work with existing information. First, the method is tested on data from a dedicated experiment, where a CML has been specifically set up for rainfall monitoring experiments, as well as operational CMLs from an existing cellular network. Second, we assess the performance for several experimental layouts of <q>ground truth</q> from rain gauges (RGs) with different spatial and temporal resolutions. The results suggest that CMLs adjusted by RGs with a temporal aggregation of up to 1 h (i) provide precise high-resolution QPEs (relative error  &lt;&thinsp;7 %, Nash&ndash;Sutcliffe efficiency coefficient  &gt;  0.75) and (ii) that the combination of both sensor types clearly outperforms each individual monitoring system. Unfortunately, adjusting CML observations to RGs with longer aggregation intervals of up to 24 h has drawbacks. Although it substantially reduces bias, it unfavourably smoothes out rainfall peaks of high intensities, which is undesirable for stormwater management. A similar, but less severe, effect occurs due to spatial averaging when CMLs are adjusted to remote RGs. Nevertheless, even here, adjusted CMLs perform better than RGs alone. Furthermore, we provide first evidence that the joint use of multiple CMLs together with RGs also reduces bias in their QPEs. In summary, we believe that our adjustment method has great potential to improve the space&ndash;time resolution of current urban rainfall monitoring networks. Nevertheless, future work should aim to better understand the reason for the observed systematic error in QPEs from CMLs.

Frances C Moore, Uris Lantz C Baldos, Thomas Hertel

A large number of studies have been published examining the implications of climate change for agricultural productivity that, broadly speaking, can be divided into process-based modeling and statistical approaches. Despite a general perception that results from these methods differ substantially, there have been few direct comparisons. Here we use a data-base of yield impact studies compiled for the IPCC Fifth Assessment Report (Porter et al 2014 ) to systematically compare results from process-based and empirical studies. Controlling for differences in representation of CO _2 fertilization between the two methods, we find little evidence for differences in the yield response to warming. The magnitude of CO _2 fertilization is instead a much larger source of uncertainty. Based on this set of impact results, we find a very limited potential for on-farm adaptation to reduce yield impacts. We use the Global Trade Analysis Project (GTAP) global economic model to estimate welfare consequences of yield changes and find negligible welfare changes for warming of 1 °C–2 °C if CO _2 fertilization is included and large negative effects on welfare without CO _2 . Uncertainty bounds on welfare changes are highly asymmetric, showing substantial probability of large declines in welfare for warming of 2 °C–3 °C even including the CO _2 fertilization effect.

A. J. Coletti, R. M. DeConto, J. Brigham-Grette et al.

Until now, the lack of time-continuous, terrestrial paleoenvironmental data from the Pleistocene Arctic has made model simulations of past interglacials difficult to assess. Here, we compare climate simulations of four warm interglacials at Marine Isotope Stages (MISs) 1 (9 ka), 5e (127 ka), 11c (409 ka) and 31 (1072 ka) with new proxy climate data recovered from Lake El'gygytgyn, NE Russia. Climate reconstructions of the mean temperature of the warmest month (MTWM) indicate conditions up to 0.4, 2.1, 0.5 and 3.1 °C warmer than today during MIS 1, 5e, 11c and 31, respectively. While the climate model captures much of the observed warming during each interglacial, largely in response to boreal summer (JJA) orbital forcing, the extraordinary warmth of MIS 11c compared to the other interglacials in the Lake El'gygytgyn temperature proxy reconstructions remains difficult to explain. To deconvolve the contribution of multiple influences on interglacial warming at Lake El'gygytgyn, we isolated the influence of vegetation, sea ice and circum-Arctic land ice feedbacks on the modeled climate of the Beringian interior. Simulations accounting for climate–vegetation–land-surface feedbacks during all four interglacials show expanding boreal forest cover with increasing summer insolation intensity. A deglaciated Greenland is shown to have a minimal effect on northeast Asian temperature during the warmth of stages 11c and 31 (Melles et al., 2012). A prescribed enhancement of oceanic heat transport into the Arctic Ocean does have some effect on Lake El'gygytgyn's regional climate, but the exceptional warmth of MIS l1c remains enigmatic compared to the modest orbital and greenhouse gas forcing during that interglacial.

B. Gräler, M. J. van den Berg, S. Vandenberghe et al.

Most of the hydrological and hydraulic studies refer to the notion of a return period to quantify design variables. When dealing with multiple design variables, the well-known univariate statistical analysis is no longer satisfactory, and several issues challenge the practitioner. How should one incorporate the dependence between variables? How should a multivariate return period be defined and applied in order to yield a proper design event? In this study an overview of the state of the art for estimating multivariate design events is given and the different approaches are compared. The construction of multivariate distribution functions is done through the use of copulas, given their practicality in multivariate frequency analyses and their ability to model numerous types of dependence structures in a flexible way. A synthetic case study is used to generate a large data set of simulated discharges that is used for illustrating the effect of different modelling choices on the design events. Based on different uni- and multivariate approaches, the design hydrograph characteristics of a 3-D phenomenon composed of annual maximum peak discharge, its volume, and duration are derived. These approaches are based on regression analysis, bivariate conditional distributions, bivariate joint distributions and Kendall distribution functions, highlighting theoretical and practical issues of multivariate frequency analysis. Also an ensemble-based approach is presented. For a given design return period, the approach chosen clearly affects the calculated design event, and much attention should be given to the choice of the approach used as this depends on the real-world problem at hand.

Y.H. FAURE, M. VERSTAEVEL, P. MÉRIAUX et al.

Les risques liés au vieillissement des géotextiles-filtres utilisés dans le drainage constituent un enjeu majeur pour l'ingénierie des glissements de terrain et des ouvrages hydrauliques. Le projet DrainAgeing vise à mieux comprendre des phénomènes de vieillissement, notamment de colmatage, des drains afin de mieux les prévenir. Cet article présente l'état d'avancement du projet et les résultats de quelque dix-sept années de suivi du dispositif expérimental de tranchées drainantes de Roissard, qui en constitue le support. On conclut sur les perspectives pour la mise en œuvre d'une deuxième phase du projet consistant à excaver, prélever et analyser des échantillons de géosynthétiques et géomatériaux sur le site expérimental.

L. D. Sánchez, L. M. Marin, J. T. Visscher et al.

This paper assesses the operational and design aspects of coagulation and flocculation in upflow gravel filters (CF-UGF) in a multi-stage filtration (MSF) plant. This study shows that CF-UGF units improve the performance of MSF considerably, when the system operates with turbidity above 30 NTU. It strongly reduces the load of particulate material before the water enters in the slow sand filters (SSF) and therewith avoids short filter runs and prevents early interruption in SSF operations. The removal efficiency of turbidity in the CF-UGF with coagulant was between 85 and 96%, whereas the average efficiency without coagulant dosing was 46% (range: 21&amp;ndash;76%). Operating with coagulant also improves the removal efficiency for total coliforms, &lt;i&gt;E-coli&lt;/i&gt; and HPC. No reduction was observed in the microbial activity of the SSF, no obstruction of the SSF bed was demonstrated and SSF runs were maintained between 50 and 70 days for a maximum head loss of 0.70 m. The most important advantage is the flexibility of the system to operate with and without coagulant according to the influent turbidity. It was only necessary for 20% of the time to operate with the coagulant. The CF-UGF unit represented 7% of total construction costs and the O&amp;M cost for the use of coagulant represented only 0.3%.