The pollution of water resources due to the disposal of industrial wastes that have organic material like phenol is causing worldwide concern because of their toxicity towards aquatic life, human beings and the environment. Phenol causes nervous system damage, renal kidney disease, mental retardation, cancer and anaemia. In this study, magnetic palm kernel biochar is used for removal of phenol from wastewater. The effect of parameters such as pH, agitation speed, contact time and magnetic biochar dosage are validated using design of experiments. The statistical analysis reveals that the optimum conditions for the highest removal (93.39%) of phenol are obtained at pH of 8, magnetic biochar dosage of 0.6 g, agitation speed at 180 rpm and time of 60 min with the initial concentration of 10 mg/L. The maximum adsorption capacities of phenol were found to be 10.84 mg/g and Langmuir and Freundlich isotherm models match the experimental data very well and adsorption kinetic obeys a pseudo-second order. Hence, magnetic palm kernel can be a potential candidate for phenol removal from wastewater.
Environmental exposure to active pharmaceutical ingredients (APIs) can have negative effects on the health of ecosystems and humans. While numerous studies have monitored APIs in rivers, these employ different analytical methods, measure different APIs, and have ignored many of the countries of the world. This makes it difficult to quantify the scale of the problem from a global perspective. Furthermore, comparison of the existing data, generated for different studies/regions/continents, is challenging due to the vast differences between the analytical methodologies employed. Here, we present a global-scale study of API pollution in 258 of the world's rivers, representing the environmental influence of 471.4 million people across 137 geographic regions. Samples were obtained from 1,052 locations in 104 countries (representing all continents and 36 countries not previously studied for API contamination) and analyzed for 61 APIs. Highest cumulative API concentrations were observed in sub-Saharan Africa, south Asia, and South America. The most contaminated sites were in low- to middle-income countries and were associated with areas with poor wastewater and waste management infrastructure and pharmaceutical manufacturing. The most frequently detected APIs were carbamazepine, metformin, and caffeine (a compound also arising from lifestyle use), which were detected at over half of the sites monitored. Concentrations of at least one API at 25.7% of the sampling sites were greater than concentrations considered safe for aquatic organisms, or which are of concern in terms of selection for antimicrobial resistance. Therefore, pharmaceutical pollution poses a global threat to environmental and human health, as well as to delivery of the United Nations Sustainable Development Goals.
The mineralisation kinetics of petroleum refinery effluent (PRE) by Fenton oxidation were evaluated. Within the ambit of the experimental data generated, first-order kinetic model (FKM), generalised lumped kinetic model (GLKM), and generalized kinetic model (GKM) were tested. The obtained apparent kinetic rate constants for the initial oxidation step (k'2), their final oxidation step (k'1), and the direct conversion to endproducts step (k3') were 10.12, 3.78, and 0.24 min(-1) for GKM; 0.98, 0.98, and nil min(-1) for GLKM; and nil, nil, and >0.005 min(-1) for FKM. The findings showed that GKM is superior in estimating the mineralization kinetics.
Two types of flow system, free surface flow (FSF) and sub-surface flow (SSF), were examined to select a better way to remove total petroleum hydrocarbons (TPH) using diesel as a hydrocarbon model in a phytotoxicity test to Scirpus grossus. The removal efficiencies of TPH for the two flow systems were compared. Several wastewater parameters, including temperature (T, °C), dissolved oxygen (DO, mgL(-1)), oxidation-reduction potential (ORP, mV), and pH were recorded during the experimental runs. In addition, overall plant lengths, wet weights, and dry weights were also monitored. The phytotoxicity test using the bulrush plant S. grossus was run for 72 days with different diesel concentrations (1%, 2%, and 3%) (Vdiesel/Vwater). A comparison between the two flow systems showed that the SSF system was more efficient than the FSF system in removing TPH from the synthetic wastewater, with average removal efficiencies of 91.5% and 80.2%, respectively. The SSF system was able to tolerate higher diesel concentrations than was the FSF system.
Demand for online and real-time measurements techniques to meet environmental regulation and treatment compliance are increasing. However the conventional techniques, which involve scheduled sampling and chemical analysis can be expensive and time consuming. Therefore cheaper and faster alternatives to monitor wastewater characteristics are required as alternatives to conventional methods. This paper reviews existing conventional techniques and optical and fibre optic sensors to determine selected wastewater characteristics which are colour, Chemical Oxygen Demand (COD) and Biological Oxygen Demand (BOD). The review confirms that with appropriate configuration, calibration and fibre features the parameters can be determined with accuracy comparable to conventional method. With more research in this area, the potential for using FOS for online and real-time measurement of more wastewater parameters for various types of industrial effluent are promising.
As Malaysia is one of the world's largest producer of palm oil, large amounts of palm oil mill effluent (POME) is generated. It was found that negatively charged components are accountable for POME color. An attempt was made to remove residual contaminants after conventional treatment using anion base resin. Adsorption experiments were carried out in fixed bed column. Various models such as the Thomas, the Yoon-Nelson, the Wolborska and BDST model were used to fit the experimental data. It was found that only the BDST model was fitted well at the initial breakthrough time. A wavelet neural network model (WNN) was developed to model the breakthrough curves in fixed bed column for multicomponent system. The results showed that the WNN model described breakthrough curves better than the commonly used models. The effects of pH, flow rate and bed depth on column performance were investigated. It was found that the highest uptake capacity was obtained at pH 3. The exhaustion time appeared to increase with increase in bed length and decrease in flow rate.
A lab-scale granular activated carbon sequencing batch biofilm reactor (GAC-SBBR), a combined adsorption and biological process, was developed to treat real wastewater from a recycled paper mill. In this study, one-consortia of mixed culture (4000-5000 mg/L) originating from recycled paper mill activated sludge from Kajang, Malaysia was acclimatized. The GAC-SBBR was fed with real wastewater taken from the same recycled paper mill, which had a high concentration of chemical oxygen demand (COD) and adsorbable organic halides (AOX). The operational duration of the GAC-SBBR was adjusted from 48 h to 24, 12 and finally 8 h to evaluate the effect of the hydraulic retention time (HRT) on the simultaneous removal of COD and AOX. The COD and AOX removals were in the range of 53-92% and 26-99%, respectively. From this study, it was observed that the longest HRT (48 h) yielded a high removal of COD and AOX, at 92% and 99%, respectively.
The development of eco-friendly and efficient technologies for treating wastewater is one of the attractive research area. Phytoremediation is considered to be a possible method for the removal of pollutants present in wastewater and recognized as a better green remediation technology. Nowadays the focus is to look for a sustainable approach in developing wastewater treatment capability. Water hyacinth is one of the ancient technology that has been still used in the modern era. Although, many papers in relation to wastewater treatment using water hyacinth have been published, recently removal of organic, inorganic and heavy metal have not been reviewed extensively. The main objective of this paper is to review the possibility of using water hyacinth for the removal of pollutants present in different types of wastewater. Water hyacinth is although reported to be as one of the most problematic plants worldwide due to its uncontrollable growth in water bodies but its quest for nutrient absorption has provided way for its usage in phytoremediation, along with the combination of herbicidal control, integratated biological control and watershed management controlling nutrient supply to control its growth. Moreover as a part of solving wastewater treatment problems in urban or industrial areas using this plant, a large number of useful byproducts can be developed like animal and fish feed, power plant energy (briquette), ethanol, biogas, composting and fiber board making. In focus to the future aspects of phytoremediation, the utilization of invasive plants in pollution abatement phytotechnologies can certainly assist for their sustainable management in treating waste water.
An innovative design of upflow constructed wetland-microbial fuel cell (UFCW-MFC) planted with cattail was used for simultaneous wastewater treatment and electricity generation. The electrodes material employed in the study was carbon felt. The main aim of this study is to assess the performance of the UFCW coupling with MFC in term of ability to treat wastewater and the capability to generate bioelectricity. The oxidation reduction potential (ORP) and dissolved oxygen (DO) profile showed that the anaerobic and aerobic regions were well developed in the lower and upper bed, respectively, of UFCW-MFC. Biodegradation of organic matter, nitrification and denitrification was investigated and the removal efficiencies of COD, NO3(-), NH4(+) were 100%, 40%, and 91%, respectively. The maximum power density of 6.12 mW m(-2) and coulombic efficiency of 8.6% were achieved at electrode spacing of anode 1 (A1) and cathode (15 cm).
Many wastewater treatment plants (WWTPs) operating in biological nitrogen removal activated sludge process in the tropics are facing the pressure of increasingly stringent effluent standards while seeking solutions to reduce the plants' energy consumption and operating cost. This study investigated the feasibility of applying low-dissolved oxygen (low-DO) nitrification and utilizing slowly-biodegradable chemical oxygen demand (sbCOD) for denitrification, which helps to reduce energy usage and operating cost in treating low soluble COD-to-nitrogen tropical wastewater. The tropical wastewater was first characterized using wastewater fractionation and respirometry batch tests. Then, a lab-scale sequencing batch reactor (SBR) was operated to evaluate the long-term stability of low-DO nitrification and utilizing sbCOD for denitrification in an anoxic-oxic (AO) process treating tropical wastewater. The wastewater fractionation experiment revealed that particulate settleable solids (PSS) in the wastewater provided slowly-biodegradable COD (sbCOD), which made up the major part (51 ± 10%) of the total COD. The PSS hydrolysis rate constant at tropical temperature (30 °C) was 2.5 times higher than that at 20 °C, suggesting that sbCOD may be utilized for denitrification. During the SBR operation, high nitrification efficiency (93 ± 6%) was attained at low-DO condition (0.9 ± 0.1 mg O2/L). Utilizing sbCOD for post-anoxic denitrification in the SBR reduced the effluent nitrate concentration. Quantitative polymerase chain reaction, 16S rRNA amplicon sequencing and fluorescence in-situ hybridization revealed that the genus Nitrospira was a dominant nitrifier. 16S rRNA amplicon sequencing result suggested that 50% of the Nitrospira-related operational taxonomic units were affiliated with comammox, which may imply that the low-DO condition and the warm wastewater promoted their growth. The nitrogen removal in a tropical AO process was enhanced by incorporating low-DO nitrification and utilizing sbCOD for post-anoxic denitrification, which contributes to an improved energy sustainability of WWTPs.
The state of activated sludge wastewater treatment process (AS WWTP) is conventionally identified by physico-chemical measurements which are costly, time-consuming and have associated environmental hazards. Image processing and analysis-based linear regression modeling has been used to monitor the AS WWTP. But it is plant- and state-specific in the sense that it cannot be generalized to multiple plants and states. Generalized classification modeling for state identification is the main objective of this work. By generalized classification, we mean that the identification model does not require any prior information about the state of the plant, and the resultant identification is valid for any plant in any state. In this paper, the generalized classification model for the AS process is proposed based on features extracted using morphological parameters of flocs. The images of the AS samples, collected from aeration tanks of nine plants, are acquired through bright-field microscopy. Feature-selection is performed in context of classification using sequential feature selection and least absolute shrinkage and selection operator. A support vector machine (SVM)-based state identification strategy was proposed with a new agreement solver module for imbalanced data of the states of AS plants. The classification results were compared with state-of-the-art multiclass SVMs (one-vs.-one and one-vs.-all), and ensemble classifiers using the performance metrics: accuracy, recall, specificity, precision, F measure and kappa coefficient (κ). The proposed strategy exhibits better results by identification of different states of different plants with accuracy 0.9423, and κ 0.6681 for the minority class data of bulking.
The objective of this study was to investigate several operating parameters, such as open circuit, different external resistance, pH, supporting electrolyte, and presence of aeration that might enhance the degradation rate as well as electricity generation of batik wastewater in solar photocatalytic fuel cell (PFC). The optimum degradation of batik wastewater was at pH 9 with external resistor 250 Ω. It was observed that open circuit of PFC showed only 17.2 ± 7.5% of removal efficiency, meanwhile the degradation rate of batik wastewater was enhanced to 31.9 ± 15.0% for closed circuit with external resistor 250 Ω. The decolorization of batik wastewater in the absence of photocatalyst due to the absorption of light irradiation by dye molecules and this process was known as photolysis. The degradation of batik wastewater increased as the external resistor value decreased. In addition, the degradation rate of batik wastewater also increased at pH 9 which was 74.4 ± 34.9% and at pH 3, its degradation rate was reduced to 19.4 ± 8.7%. The presence of aeration and sodium chloride as supporting electrolyte in batik wastewater also affected its degradation and electricity generation. The maximum absorbance of wavelength (λmax) of batik wastewater at 535 nm and chemical oxygen demand gradually decreased as increased in irradiation time; however, batik wastewater required prolonged irradiation time to fully degrade and mineralize in PFC system.
Microalgal biomass produced from the phycoremediation of wastewater represents an important protein source, lipids, and natural antioxidants and bioproducts. Therefore, the microalgal biomass and their derived compounds are used in animal and aquaculture feed as well as human nutrition and health products. Many microalgal species have shown promising potential for many bioproducts. However, significant processes to find the optimum quality and quantity of microalgal biomass are still required especially when it is used as a replacement for aquaculture feed. The limitations lie in the selection of microalgal species and their production. The present review discusses the potential generation of bioproducts from microalgal biomass resulting from the phycoremediation of wet market wastewater. The consortium approach in wastewater treatment and the comparison between biomass production and available common feeds for aquaculture were reviewed.
The scarcity of water resources and environmental pollution have highlighted the need for sustainable wastewater treatment. Existing conventional treatment systems are energy-intensive and not always able to meet stringent disposal standards. Recently, algal-bacterial systems have emerged as environmentally friendly sustainable processes for wastewater treatment and resource recovery. The algal-bacterial systems work on the principle of the symbiotic relationship between algae and bacteria. This paper comprehensively discusses the most recent studies on algal-bacterial systems for wastewater treatment, factors affecting the treatment, and aspects of resource recovery from the biomass. The algal-bacterial interaction includes cell-to-cell communication, substrate exchange, and horizontal gene transfer. The quorum sensing (QS) molecules and their effects on algal-bacterial interactions are briefly discussed. The effect of the factors such as pH, temperature, C/N/P ratio, light intensity, and external aeration on the algal-bacterial systems have been discussed. An overview of the modeling aspects of algal-bacterial systems has been provided. The algal-bacterial systems have the potential for removing micropollutants because of the diverse possible interactions between algae-bacteria. The removal mechanisms of micropollutants - sorption, biodegradation, and photodegradation, have been reviewed. The harvesting methods and resource recovery aspects have been presented. The major challenges associated with algal-bacterial systems for real scale implementation and future perspectives have been discussed. Integrating wastewater treatment with the algal biorefinery concept reduces the overall waste component in a wastewater treatment system by converting the biomass into a useful product, resulting in a sustainable system that contributes to the circular bioeconomy.
Aerobic dynamic feeding (ADF) strategy was applied in sequencing batch reactor (SBR) to accumulate polyhydroxyalkanoate (PHA) in aerobic granules. The aerobic granules were able to remove 90% of the COD from palm oil mill effluent (POME). The volatile fatty acids (VFAs) in the POME are the sole source of the PHA accumulation. In this work, 100% removal of propionic and butyric acids in the POME were observed. The highest amount of PHA produced in aerobic granules was 0.6833mgPHA/mgbiomass. The PHA formed was identified as a P (hydroxybutyrate-co-hydroxyvalerate) P (HB-co-HV).
The paper demonstrates the capability of using cockle shells as an adsorbent for phosphorus removal from simulated petrochemical wastewater, focusing on the actual condition of the petrochemical facultative pond. In this study, the physicochemical properties of shell powder were determined, such as the functional groups, surface morphology, crystalline structure, and surface area using FTIR, SEM, EDX, XRD, and BET. It was observed that the optimum conditions for effective phosphorus removal are under the presence of rotational speed (125 rpm), higher dosage (7 g/L), and larger surface area (smaller particle size) of the shell powder. Fine powder achieved up to 52.27% of phosphorus removal after 40 min compared to coarse powder which could only give 16.67% removal. Additionally, calcined shell powder demonstrated a higher phosphorus removal rate, i.e., up to 62.37%, compared to raw shell powders. The adsorption isotherm was studied using Langmuir and Freundlich models, but the isothermal data fit better for the Freundlich model (R2 = 0.9836). Overall, this study has successfully generated a greener and low-cost adsorbent.
The wide application of microalgae in the field of wastewater treatment and bioenergy source has improved research studies in the past years. Microalgae represent a good source of biomass and bio-products which are used in different medical and industrial activities, among them the production of high-valued products and biofuels. The present review focused on greywater treatment through the application of phycoremediation technique with microalgae and presented recent advances in technologies used for harvesting the microalgae biomass. The advantages and disadvantages of each method are discussed. The microbiological aspects of production, harvesting and utilization of microalgae biomass are viewed.
Macrophytes have been used to mitigate eutrophication and upgrade effluent quality via their nutrient removal capability. However, the available data are influenced by factors such as microbial activities, weather, and wastewater quality, making comparison between nutrient removal performance of different macrophytes almost impossible. In this study, phytoremediation by Spirodela polyrhiza, Salvinia molesta and Lemna sp. were carried out axenically in synthetic wastewater under controlled condition to precisely evaluate nutrient removal efficiency of NO3--N, PO43-, NH3-N, COD and pH in the water sample. The results showed that ammonia removal was rapid, significant for S. polyrhiza and Lemna sp., with efficiency of 60% and 41% respectively within 2 days. S. polyrhiza was capable of reducing 30% of the nitrate. Lemna sp. achieved the highest phosphate reduction of 86% at day 12 to mere 1.07 mg/L PO43--P. Correlation was found between COD and TC, suggesting the release of organic substances by macrophytes into the medium. All the macrophytes showed biomass increment. S. polyrhiza outperformed other macrophytes in nutrient removal despite lower biomass production. The acquired nutrient removal profiles can serve as a guideline for the selection of suitable macrophytes in wastewater treatment and to evaluate microbial activity in non-aseptic phytoremediation system.