Removal of Emerging Contaminants from Wastewater Streams Using Membrane Bioreactors: A Review

Water is a very valuable natural resource. As the demand for water increases the presence of emerging contaminants in wastewater has become a growing concern. This is particularly true when one considers direct reuse of wastewater. Obtaining sufficient removal of emerging contaminants will require determining the level of removal for the various unit operations in the wastewater treatment process. Membrane bioreactors are attractive as they combine an activated sludge process with a membrane separation step. They are frequently used in a wastewater treatment process and can operate at higher solid loadings than conventional activated sludge processes. Determining the level of removal of emerging contaminants in the membrane bioreactor step is, therefore, of great interest. Removal of emerging contaminants could be by adsorption onto the biomass or membrane surface, biotransformation, size exclusion by the membrane, or volatilization. Given the fact that most emerging contaminants are low molecule weight non-volatile compounds, the latter two methods of removal are usually unimportant. However, biotransformation and adsorption onto the biomass are important mechanisms of removal. It will be important to determine if the microorganisms present at given treatment facility are able to remove ECs present in the wastewater.

Hydroxylamine Accelerates the Cycle of Fe(III)/Fe(II)-Cu(II)/Cu(I) to Enhance the Ability of Fe-Cu Bimetallic System to Activate Peroxymonosulfate to Degrade AO7

In this study, a new type of iron/copper bimetallic combined with hydroxylamine (HA) activated peroxymonosulfate (PMS) was constructed to treat organic pollutants. Selecting the azo dye AO7 as the representative of organic pollutants, the new system can achieve nearly 100% degradation of AO7 within 5 minutes. The Fe(Ⅲ)/Cu(Ⅱ)/HA/PMS system mainly generates SO4·- to achieve the degradation of AO7 in acidic environment, while neutral and alkaline environments rely on ·OH. The presence of hydroxylamine accelerates the cycle of Fe(Ⅲ)/Fe(Ⅱ) and Cu(Ⅱ)/Cu(Ⅰ) in the system, and enhances the degradation ability of the system for organic pollutants. The addition of trace Cu(Ⅱ) (1 μM) enhances the ability of a single Fe(Ⅲ)/HA/PMS system to degrade AO7 in neutral and alkaline environments without causing secondary copper pollution. The common inorganic anions Cl- and NO3- in water have almost no effect on the degradation of AO7 in the system. The constructed Fe(Ⅲ)/Cu(Ⅱ)/HA/PMS system is an efficient and clean organic pollutant wastewater treatment process, which has very promising application prospects.

The promising applications of nanoparticles for synthetic dyes removal from wastewater: recent review

PurposeWater is a vital natural resource without which life on earth would be impossible. Properties of synthetic dyes like high stability and noxious nature make it difficult to remove them from the effluent. This review focuses on the removal of synthetic dyes using nanoparticles (NPs) based on the adsorption principle.Design/methodology/approachAdsorption technique is widely used to remove synthetic dyes from their aqueous solution for decades. Synthetic dye removal using NPs is promising, less energy-intensive and has become popular in recent years. NPs are in high demand for treating wastewater using the adsorption principle due to their tiny size and vast surface area. To maximise environmental sustainability, the utilisation of green-produced NPs as efficient catalysts for dye removal has sparked attention amongst scientists.FindingsThis review has prioritised research and development of optimal dye removal systems that can be used to efficiently remove a large quantity of dye in a short period while safeguarding the environment and producing fewer harmful by-products. The removal efficiency of synthetic dye using different NPs in wastewater treatment varies mostly between 75% to almost 100%. This review will aid in the scaling up of the wastewater treatment process.Research limitations/implicationsThere is a lack of research emphasis on the safe disposal of NPs once the reuse efficiency significantly drops. The relevance of cost analysis is equally critical, yet only a few papers discuss cost-related information.Originality/valueComprehensive and planned research in this area can aid in the development of long-term wastewater treatment technology to meet the growing need for safe and reliable water emphasising reuse and desorption efficiency of the NPs.

Modeling and optimizations of mixing and aeration processes in bioreactors with activated sludge

Mixing aimed at homogenization of the volume of bioreactors with the activated sludge is of great importance for the proper course of the wastewater treatment process. It affects both the efficiency of pollutants removal and the properties of the activated sludge related to its sedimentation. The mixing process in bioreactors can be carried out in different ways. In batch bioreactors in the aeration phase or flow bioreactors in aerobic chambers, mixing is carried out through aeration systems. These systems should aerate the activated sludge flocs for efficient biological treating of wastewater, as well as effectively homogenize the volume of the bioreactor. Hence, it is important to choose such a design of the aeration system and its operation settings that provide the amount of air ensuring the exact amount of oxygen for the implementation of technological processes, counteract sedimentation of sludge at the bottom of the reactor, are reliable as well as economical in operation (demand of electric energy). The paper presents the model studies aimed at optimization of the design and settings of aeration and mixing systems used in active sludge bioreactors.

Wastewater deodorization: problems and solutions

The problem of specific malodours odorants, emitted from the territory of wastewater and sludge treatment facilities is set in the article. This article presents a critical review concerning the reasons of odorants formation during wastewater treatment, their influence on human health and ways of wastewater and sludge deodorization. Review is presented by 52 resources of Russian, Chinese, Italian, Greek, Indian, American and other researches from 2000 to 2021 years. According to the review the main sources of odours emission are units of mechanical treatment, sludge thickening and sludge digestion. The main odorants are volatile organic compounds (VOCs), hydrogen sulphide, ammonia, particulate matters and greenhouse gases (carbon dioxide, methane, nitrogen oxide). Based on the article, there are two ways of emission controlling: controlling the technological parameters of wastewater treatment process or gases treatment at specific facilities (adsorbers, biofilters, bioscrubbers, chemical scrubbers).

Determination of the Optimal Parameters of the Jet Aeration

To ensure effective aeration of the biological wastewater treatment process, easy-to-operate and not too energy-intensive units are needed. Jet aerators have such capabilities. In this study, the authors searched for the best hole shape for the aeration nozzles. It was determined that a nozzle with an elongated hole has the largest size of the actively aerated zone. Experimental studies of nozzles of a diameter of 56 mm with nozzles of elongated shape showed that the best characteristics of mass transfer are provided by nozzles with a total area of holes of 356 mm2 at a flow rate of 10 … 12 m/s. For practical calculations, an equation was obtained for the dependence of the oxygen transfer coefficient KLa(20) on the complex criterion vn, and a method for calculating aeration units was developed, which is applicable for aerators with elongated holes.