Performance of an innovative multi-stage anaerobic reactor during start-up period

Start-up of an anaerobic reactor is a relatively delicate process and depends on various factors such as wastewater composition, available inoculum, operating conditions and reactor configuration. Accordingly, systematized operational procedures are important, mainly during the start-up of an anaerobic reactor. In this paper, the start-up performance of an innovative multi-stage anaerobic reactor using synthetic wastewater at various organic loading rates (OLRs) was investigated. In Phase 1 of the experimental study, the reactor was operated at hydraulic retention time (HRT) of 1 day with corresponding OLR of 1.07 kg COD.m-3.d-1. Thereafter, the reactor was operated at intermittent feeding (Phase 2), with HRT of 1.4 day and OLR of 0.82 to 2.45 kg COD.m-3.d-1. Results showed up to 71% COD reduction in the Phase 1 of the experimental study. However, in Phase 2, when the reactor was operated at intermittent feeding, the COD removal efficiency increased from 75 to 92%. It can be concluded that the multi-stage anaerobic reactor system performed better at intermittent feeding, indicating that the reactor required low loading rate and sufficient HRT for gradual acclimatization for reactor start-up. The reduction of the period necessary for the start-up and improved operational control are important factors to increase the efficiency the reactor system.Key words: Anaerobic reactor start-up, biomass, glucose wastewater, intermittent feeding, multi-stage anaerobic reactor

Potential of Microalgae in Bioremediation of Wastewater

The increase in global pollution, industrialization and fast economic progress are considered to inflict serious consequences to the quality and availability of water throughout the world. Wastewater is generated from three major sources, i.e. industrial, agricultural, and municipal which contain pollutants, such as: xenobiotics, microplastics, heavy metals and augmented by high amount of carbon, phosphorus, and nitrogen compounds. Wastewater treatment is one of the most pressing issues since it cannot be achieved by any specific technology because of the varying nature and concentrations of pollutants and efficiency of the treatment technologies. The degradation capacity of these conventional treatment technologies is limited, especially regarding heavy metals, nutrients, and xenobiotics, steering the researchers to bioremediation using microalgae (Phycoremediation). Bioremediation can be defined as use of microalgae  for removal or biotransformation of pollutants and CO2 from wastewater with concomitant biomass production. However, the usage of wastewaters for the bulk cultivation of microalgae is advantageous for reducing carbon, nutrients cost, minimizing the consumption of freshwater, nitrogen, phosphorus recovery, and removal of other pollutants from wastewater and producing sufficient biomass for value addition for either biofuels or other value-added compounds. Several types of microalgae like Chlorella and Dunaliella have proved their applicability in the treatment of wastewaters. The bottlenecks concerning the microalgal wastewater bioremediation need to be identified and elucidated to proceed in bioremediation using microalgae. This objective of this paper is to provide an insight about the treatment of different wastewaters using microalgae and microalgal potential in the treatment of wastewaters containing heavy metals and emerging contaminants, with the specialized cultivation systems. This review also summarizes the end use applications of microalgal biomass which makes the bioremediation aspect more environmentally sustainable. Copyright © 2021 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).

Flash flood susceptibility modelling: a review

Flash flood is common problem in the developed or developing country especially in urban areas. This is due to the changes of land use, poor planning of drainage system, deforestation and unplanned land use and etc. Flash flood susceptibility modelling (FFSM) for urban area is important to avoid the loss and etc. FFSM can be vital component and essential tools for planning and management of natural disaster and environmental. The objective of this paper is to review selected paper on flash flood susceptibility modelling using Geographic Information System (GIS) coupling empirical models. A lot of methods have been coupling with GIS to developed flood susceptibility modelling, for example, Weight of Evidence, Random Forest, etc. However, there is still lack of susceptibility model for flash flood. The GIS coupling method can improve the accuracy of flood susceptibility modelling. Thus, this paper will review the ability of GIS coupling with empirical models for the flash flood susceptibility modelling

Photocatalytic removal of malachite green and brilliant blue dyes from its aqueous solution: a case study of factorial experimental design

In this present study, the investigation of the photocatalytic removal of malachite green and brilliant blue dyes from their aqueous solution using photocatalytic oxidation process was provided. The application of factorial experimental design for the analysis the results was the main objective in the present study. The photocatalytic removal of Malachite Green (MG) and Brilliant Blue (BB) dyes was carried out in aqueous solutions containing the dye and suspended of ZnO upon UV irradiation (high pressure mercury lamp Radium 125 W). The effect of different factors such as initial dye concentration, sample volume and treatment time was taken in account. All samples of MG and BB have been analysed at 617 and 620 nm, respectively. The linearity ranged between 5 and 50 mg/L for MG dye while it was ranged between 20 and 200 mg/L for BB dye. The linear regression, R2, was more than 0.995 for both dyes. The results revealed that factorial experimental design analysis has given a better indication to investigate the effects of factors. It was observed that the most of factors are significant for both dyes. Initial concentration and treatment time factors were the most significant factors for MG and BB dyes, respectively according to pareto chart

Occurrence and distribution of 17 targeted human pharmaceuticals in various aquatic environmental matrices in southeast asia with particular reference to malaysia: a comprehensive review

This review focuses on the occurrence and distribution of 17 targeted human pharmaceutical compounds from the most common therapeutic classes. These include one analgesic (acetaminophen), three non-steroidal anti-inflammatory drugs (NSAIDs) (acetylsalicylic acid, diclofenac, ibuprofen), two antidiabetic drugs (gliclazide, metformin), three antihistamines (cetirizine, chlorphenamine, ranitidine), four antihypertensives (amlodipine, atenolol, metoprolol, prazosin), one lipid regulator (simvastatin), one anti-convulsant (carbamazepine), one bronchodilator agent (salbutamol) and one stimulant (caffeine) which have been detected globally in various aquatic environmental matrices such as surface water, drinking water, ground water, seawater, influent and effluent of municipal wastewater treatment plants (WWTPs), hospital and industrial treatment plants, among others. The most common analytical method used involved solid phase extraction (SPE) and liquid chromatography coupled to mass spectrometry. The concentrations of all drugs investigated in all aqueous matrices varied from 0.5 to 85,000 ng/L for the highest concentration in the aqueous matrices in Southeast Asia. This review provides the first compilation on human pharmaceuticals in Southeast Asia in surface water, domestic wastewater (influent and effluent) and drinking water

Transportation of different therapeutic classes of pharmaceuticals to the surface water, sewage treatment plant, and hospital samples, Malaysia

All pharmaceuticals are separated chromatographically using the liquid chromatographytime of flight/mass spectrometry (LC-ToF/MS) on a 5 μm, 2.1 mm × 250 mm, C18 column at 0.3 mL/min. The recovery is investigated at two spiking levels, 10 and 1 ng/mL; the mean recovery is higher than 77, 84, and 93% in sewage treatment plants (STP) influent, STP effluent, and surface water, respectively. The limit of quantification (LOQ) averages 29, 16, 7, and 2 ng/L in STP influent, STP effluent, surface water, and drinking water, respectively. The matrix effect is also evaluated in STP influent and effluent. It is observed that sulfamethoxazole, prednisolone, ketoprofen, and glibenclamide are highly impacted compared to other compounds, -99, -110, 77, and 91%, respectively. The results show that six out of nine pharmaceuticals, namely atenolol, acetaminophen, theophylline, caffeine, metoprolol, and sulfamethoxazole are detected in STP influent, STP effluent, and surface water. However, the means of concentration are 561, 3305, 1805, 3900, 78, and 308 ng/L for atenolol, acetaminophen, theophylline, caffeine, metoprolol, and sulfamethoxazole, respectively, in STP influent. Caffeine and acetaminophen are detected with the highest concentration, reaching up to 8700 and 4919 ng/L, respectively, in STP influent

Elucidation and characterization of new chlorinated by-products after electrochemical degradation of hydrochlorothiazide using graphite poly vinyl chloride electrode

This paper describes an electrochemical treatment process of hydrochlorothiazide (HDZ) under different conditions such as initial concentration, sodium chloride and applied voltage. In this present study, HDZ was treated by electrochemical oxidation process using graphite-PVC composite electrode as anode and Platinum (Pt) as cathode. All results were analyzed using liquid chromatography-time of flight/mass spectrometry (LC-TOF/MS). It was found that at high applied voltages, and high amounts of NaCl, the electrochemical treatment process was more efficient. The removal% of HDZ was 92% at 5 V after 60 min. From the obtained results, the electrochemical oxidation process of HDZ followed pseudo first order with rate constant values ranged between 0.0009 and 0.0502 min−1, depending on the experimental conditions. Energy consumption was also considered in this study, it was ranged between 0.9058 and 5.56 Wh/mg using 0.5, 0.3 and 0.1 g NaCl within interval times of (10, 20, 30, 40, 50, 60, 70, and 80 min). Five chlorinated and one non-chlorinated by-products were formed and analyzed in negative ionization (NI) mode during the electrochemical process. Due to the strong oxidizing potential of the chlorine (Cl2) and hypochlorite ion (ClO−), HDZ and its by-products were removed after 140 min. Furthermore, a novel synthesis of chlorothiaizde as one of the new by-products was reported in this present study. Toxicity was impacted by the formation of the by-products, especially at 20 min. The inhibition percentage (I%) of E. coli bacteria was decreased to be the lowest value after 140 min

Flood mapping using sentinel-1 SAR imagery: case study of the November 2017 flood in Penang

The Sentinel-1 SAR image by the Europe Space Agency (ESA) in the Copernicus Programme is an open source data which offers good data to develop flood inundation mapping. The flood inundation mapping is essential information for local authority personals or researchers to develop flood inventory map. The objective of this study is to develop a flood inundation mapping on November 2017 event to assess its use as potential flood inventory mapping data in Penang. The threshold method was carried out using Sentinel-1 image to extract the flood map. This method is pixel value used to separate the grey image into two parts. The flooded and non-flooded areas can be identified by separating the backscatter lower than the threshold value. The results revealed that the flood inundation maps are able to be extracted out from Sentinel-1 images

Application of carbon nanotubes and graphene to develop the heavy metal electrochemical sensor

Carbon nanotubes (CNTs) and graphene are carbon-based materials with great potential for electrochemical sensing in various applications such as for the environmental, biological, and physical sensors. For environmental applications, the sensor used to detect heavy metals such as cadmium (Cd), lead (Pb), mercury (Hg), iron (Fe), and other heavy metals that present in the water qualitatively and at the lowest limit of detection value. The uniqueness of their structures and chemical properties has attracted many researchers to develop carbon-based electrochemical sensors for environmental applications. These carbon materials are low-dimensional, thus providing the elevated aspect ratios and subsequently able to increase the sensitivity of the sensor probe. In the meantime, the graphene has its advantages in terms of its large surface area per unit volume to absorb and trap the molecules on the surface. In theory, the carbon atom is in the mid-range of electronegativity and can thus form a stable covalent bond with other molecules. These two materials are therefore consistent to bond with other functional groups such as amine, aldehyde, carboxyl, and thiol groups. All these functional groups can be functionalized with specific ligands or receptors for that particular heavy metal to provide specific and sensitive detection. Convenience in terms of their functionality, making them the center of attention as versatile platforms for functionalizing and designing an electrochemical sensor probe based on applications of concern. This paper focuses on reviewing carbon-based electrochemical sensors development to detect heavy metal in water for real-time monitoring of water quality, thus providing a brief overview of the sensor design reported previously