Search results for "removal"

Solids and Hydraulic Retention Time Effect on N2O Emission from Moving-Bed Membrane Bioreactors

2018

Biological nutrient removal was operated at different solids (SRT) and hydraulic retention times (HRT) in order to assess their influence on nitrous oxide (N2O) emission from a hybrid moving-bed membrane bioreactor. The observed results show that the N2O production decreased when the SRT/HRT was decreased. The maximum N2O gaseous concentration was measured in the aerobic reactor at the end of phase I, and it decreased through phases II and III. From mass balances over the reactors of the system, the aerated (aerobic and membrane) reactors were the largest producers of N2O, showing that the greater part of N2O was produced during the nitrification process.

Comparison of the clinical effects of white brand toothbrushes versus Vitis Suave®

2015

Background: There has been an increase in the use of white label manual toothbrushes and a greater increase in inquiries for discomfort of the gingiva and mucosa. Material and Methods: A randomized, double-blind, cross-over clinical trial was made of four white brand toothbrushes versus a control brush (Vitis Suave®), with the recording of plaque index, bleeding upon probing, and gingival abrasions following utilization of the different brushes. Results: All the brushes except Deliplus® were equally effective in terms of plaque removal ( p <0.05). Vitis Suave® and Veckia® were the brushes associated to the greatest increase in minor abrasions ( p <0.01), while Veckia®, Carrefour® and Deluxe…

Quality Standards for Recycled Water: Opuntia ficus-indica as Sorbent Material

2017

In recent years, increased industrial and agricultural activities and the correlated population growth led to overexploitation of natural resources and the increased generation of various types of pollutants. For these reasons, the hazardous pollution of wastewater is one of the most important environmental problems worldwide. A wide range of wastewater treatment technologies are available; however, some disadvantages are often reported. Hence, there is a constant need to search for an efficient, low-cost and alternative wastewater treatment. Recently, several biosolids have been considered for pollutant removal from wastewaters, including Opuntia ficus-indica. This chapter focuses on waste…

Removal of toxic pollutants from pulp mill effluents by electrocoagulation

2011

This study investigated the effect of electrocoagulation treatment on toxic pollutant removal from pulp mill effluents. Synthetic wastewaters containing wood rosin and copper or pure resin acids were used to investigate the removal of resin acids and copper by electrocoagulation. Removal of pollutants by electrocoagulation was also tested with real debarking effluent. In this study, statistical experimental design and partial least squares modeling were used to investigate the effect of initial pH, current (current density) and treatment time. Electrocoagulation and subsequent filtration removed resin acids and copper from the synthetic wastewaters with high efficiency. Toxicity to algae (P…

Semiconductor mixed oxides as innovative materials for the photocatalytic removal of organic pollutants

2020

Abstract This work aims to provide a critical survey of the extensive literature concerning the potential applications of nanostructured mixed oxides for environmental remediation. In particular, our attention was focused on the feasibility to employ these materials as photocatalysts for the elimination of toxic organic pollutants contained in water and wastewater. The advantages and perspectives of the various nanocomposites are briefly discussed.

A new approach for modeling dry deposition velocity of particles

2018

Abstract The dry deposition process is recognized as an important pathway among the various removal processes of pollutants in the atmosphere. In this field, there are several models reported in the literature useful to predict the dry deposition velocity of particles of different diameters but many of them are not capable of representing dry deposition phenomena for several categories of pollutants and deposition surfaces. Moreover, their applications is valid for specific conditions and if the data in that application meet all of the assumptions required of the data used to define the model. In this paper a new dry deposition velocity model based on an electrical analogy schema is propose…

Reduction of Nitrates in Waste Water through the Valorization of Rice Straw: LIFE LIBERNITRATE Project

2018

An improved and more sustainable waste management system is required for successful development of technologies based on renewable sources. Rice straw is submitted to controlled combustion reactions and the produced ashes are chemically treated to produce silica. After a chemical activation step, the activated silica shows potential as an adsorbent agent and will be used to remove the excess of nitrates in groundwater and wells in the area of Alginet (Valencia, Spain), selected as a vulnerable zone within the Nitrates Directive. The demonstration activity aims to have a local impact on municipalities of 200 inhabitants or fewer, decreasing from current nitrate concentrations close to 50 mg/…

Plaque removal efficacy of an electric toothbrush: a comparative study.

2008

Modelling biological and chemically induced precipitation of calcium phosphate in enhanced biological phosphorus removal systems

2011

The biologically induced precipitation processes can be important in wastewater treatment, in particular treating raw wastewater with high calcium concentration combined with Enhanced Biological Phosphorus Removal. Currently, there is little information and experience in modelling jointly biological and chemical processes. This paper presents a calcium phosphate precipitation model and its inclusion in the Activated Sludge Model No 2d (ASM2d). The proposed precipitation model considers that aqueous phase reactions quickly achieve the chemical equilibrium and that aqueous-solid change is kinetically governed. The model was calibrated using data from four experiments in a Sequencing Batch Rea…

Struvite precipitation assessment in anaerobic digestion processes

2008

Struvite precipitation causes important operational problems during the sludge treatment process, especially when EBPR sludge is treated. Predicting struvite formation is critical to be able to design process alternative that best minimises struvite precipitation. With this aim, phosphorus precipitation in an anaerobic digestion pilot plant was studied using experimental data and mass balance analysis. The results obtained showed significant phosphorus precipitation as struvite (58% of the fixed phosphorus) and a low precipitation of calcium phosphates (15%), forming mainly hydroxyapatite (HAP). The rest of the phosphorus fixed in the digester (27%) was attributed to adsorption processes on…