Modeling approach to evaluation of environmental impacts on river water quality: A case study with Galing River, Kuantan, Pahang, Malaysia

Monitoring of university wastewater within the sewage system and its performance evaluation through integrated constructed wetlands

Rapid increase in population and industrialization has not only improved the lifestyle but adversely affected the quality and availability of water leading to ample amount of wastewater generation. The major contribution towards wastewater production is from sewage. Regular monitoring and treatment of sewage water is necessary to conserve and enhance the quality of water. The present study focuses on monitoring of sewage water within the sewage system of a residential university. A total of 16 samples from different manholes were collected for physicochemical and heavy metals analysis and compared with final effluent collected from integrated constructed wetlands (ICWs) to assess its removal efficiency. The mean concentrations of influent and effluent were compared with national environmental quality standards (NEQS) for municipal discharge (pH 6-9, COD 150 mg/L, TSS 200 mg/L and TDS 3500 mg/L) and international agricultural reuse standards (IARS) (pH 6-8, COD <150 mg/L, TSS < 100 mg/L) respectively. Among all physicochemical parameters, influent values for chemical oxygen demand (COD) (169.56-258.36) mg/L exceeded the limit of NEQS for discharge into inland waters, whereas for total suspended solids (TSS) the concentration exceeded for discharge into STP (406 mg/L) and inland waters (202.33 mg/L). However, effluent concentrations for all the parameters were found within the permissible limit set by IARS. The removal efficiency for different parameters such as phosphate- phosphorus (PO43-P), COD, TSS, total dissolved solids (TDS) and total kjeldahl nitrogen (TKN) were 52, 53, 54, 35, and 36%, respectively. Heavy metal concentrations were compared with WHO guidelines among which lead (Pb) in effluent and chromium (Cr) in influent exceeded the limit (Pb 0.01 and Cr 0.05 mg/L). Interpolation results showed that zone 2 was highly contaminated in comparison to zone 1 & 3. Statistical analysis showed that correlation of physicochemical parameters and heavy metals was found significant (p < 0.05).

Causal impact analysis of enhanced phosphorus effluent standard on river water quality

The effect of environmental policies on water quality is an important factor in evaluating a project's impact and economic feasibility. The aim of this study was to evaluate the causal relationship between strengthening the total phosphorus (TP) concentration standard in wastewater treatment plant (WWTP) effluents and river water quality in the Geum River watershed (Rep. of Korea). Data, including precipitation, streamflow, and water quality, were collected for 2005-2020 and temporally divided into "before" and "after" the event of strengthening standards (in 2012). Further, the data were spatially divided into influence sites (impact) affected by the event and control sites (control) unaffected by the event. A median difference test for a before/after and control/impact (BACI) analysis and a causal impact analysis (CIA) based on a Bayesian structural time-series model were performed to evaluate the changes in water quality after the event. The BACI test showed that the TP concentration was reduced significantly (p-value<0.05) at all impact sites after the event, whereas the difference was not significant at the control sites. In contrast, other water quality variables, except TP, showed different statistical significance depending on the site. The CIA was performed by controlling the rainfall, flow rate, suspended solids, water temperature, biochemical oxygen demand, and chemical oxygen demand as covariates, which were selected based on a directed acyclic graph and bi-variable correlation analysis. The CIA results showed that the TP concentration was reduced significantly (p-value<0.05) at all impact sites, except for the control sites after the event, which is consistent with the BACI results. The causal impact of environmental management policies was previously difficult to evaluate by objectively targeting the natural systems because of the confounding bias. Our study demonstrated that strengthening the TP concentration standard from WWTPs majorly contributed to reducing TP in the receiving river, even when confounding factors, such as fluctuations in non-point source pollution loads caused by rainfall and runoff, were excluded. The statistical approaches used in this study can be valuable and practical methods for such evaluations if sufficient prior and posterior data and appropriate covariates are obtained.

Fe(iii) and Cr(vi) ions' removal using AgNPs/GO/chitosan nanocomposite as an adsorbent for wastewater treatment

Heavy metal ions in water refer to significant risks to the biological system due to their high toxicity. Therefore, the decontamination of water polluted by heavy metal ions attracts significant interest of researchers. Adsorption by nanomaterials has been a widely used technique for removing heavy metal ions from water. Chitosan was extracted from shrimp shellfish and mixed with laboratory-prepared AgNPs/GO in the ratio of 3 : 1. A series of tests evaluates the best condition of pH, amount of adsorbent, retention time, stirring speed, temp, and initial concentration. The research was conducted under various conditions. Langmuir, Freundlich, Tempkin, and Dubinin–Radushkevich isotherms were also tested. Also, the column adsorption experiment was carried out on industrial wastewater at different flow rates and column bed heights. The optimal values of the contact time, pH, and adsorbent dose of Cr(vi) were found to be 80 min, 4, and 0.1 g 100 mL⁻¹, respectively, at room temperature (30 °C), agitation at 150 rpm, and initial concentration of 50 ppm. On the other hand, the optimal value of contact time, pH, and adsorbent dose of Fe(iii) were found to be 30 min, 6, and 0.02 g 100 mL⁻¹, respectively, at room temp (30 °C) with a stirring speed of 250 rpm and an initial concentration of 40 ppm. For Cr(vi) and Fe(iii), equilibrium studies show that the data fit the Freundlich isotherm well (correlation coefficient, R² = 0.98) (III). A link between the pseudo-second order active model and data fitting the pseudo-first order active models were made. Within the intraparticle diffusion model, there are four stages that the mechanism must go through before it is at equilibrium. The adsorbent was tested in an industrial adsorbent column. This test proves that the nanocomposite's adsorption capacity can be restored by washing it with 0.1 M HCl, as shown by the periodicity test. After four cycles, the amount of Cr(vi) adsorbed on AgNPs/GO/chitosan was just 20%, which is insufficient for further adsorption experiments. Cr(vi) removal rates (%R) decreased slightly.

Steps of AgNPs/GO/chitosan nanocomposite preparation.

A Hybrid Model for Water Quality Prediction Based on an Artificial Neural Network, Wavelet Transform, and Long Short-Term Memory

Clean water is an indispensable essential resource on which humans and other living beings depend. Therefore, the establishment of a water quality prediction model to predict future water quality conditions has a significant social and economic value. In this study, a model based on an artificial neural network (ANN), discrete wavelet transform (DWT), and long short-term memory (LSTM) was constructed to predict the water quality of the Jinjiang River. Firstly, a multi-layer perceptron neural network was used to process the missing values based on the time series in the water quality dataset used in this research. Secondly, the Daubechies 5 (Db5) wavelet was used to divide the water quality data into low-frequency signals and high-frequency signals. Then, the signals were used as the input of LSTM, and LSTM was used for training, testing, and prediction. Finally, the prediction results were compared with the nonlinear auto regression (NAR) neural network model, the ANN-LSTM model, the ARIMA model, multi-layer perceptron neural networks, the LSTM model, and the CNN-LSTM model. The outcome indicated that the ANN-WT-LSTM model proposed in this study performed better than previous models in many evaluation indices. Therefore, the research methods of this study can provide technical support and practical reference for water quality monitoring and the management of the Jinjiang River and other basins.

Assessment of health risks and individuals' willingness to participate in drinking water management at flood-prone Pahang River Basin, Malaysia

Rivers, the main source of the domestic water supply in Malaysia, have been threatened by frequent flooding in recent years. This study aims to assess human health risks associated with exposure to concentrated heavy metals in a flood-prone region of Malaysia and investigate the affected individuals' willingness to participate in managing water resources. Hazard indices and cancer risks associated with water contamination by heavy metals have been assessed following the method prescribed by the US Environmental Protection Agency. Yearly data of heavy metal contamination (Cd, Cr, Pb, Zn, Fe), water quality parameters (DO, BOD, COD, pH), and climatic information (annual rainfall, annual temperature) have been collected from the Department of Environment and Meteorological Department of Malaysia, respectively. The inductively coupled plasma mass spectrometry technique has been used by the department of environment for analyzing heavy metal concentration in river water samples. In this study, data from a stratified random sample of households in the affected region were analyzed, using partial least squares structural equation modeling, to predict the link between individuals' perceptions and attitudes about water resources and their willingness to engage in water management program. The health risk estimation indicated that the hazard index values were below the acceptable limit, representing no non-carcinogenic risk to adults and children residing in the study area via oral intake and dermal adsorption of water. However, the calculated value for cancer risk signified possible carcinogenic risks associated with Pb and Cd. In general, contamination due to pollution and flooding tends to increase in the basin region, and appropriate management is needed. The results identified perceived water quality as a significant factor influencing people's attitudes toward involvement in water management programs. As in many developing countries, there is no legal provision guaranteeing public representation in water management in Malaysia. The conclusion discusses the importance of these for the literature and for informing future policy actions.

Evolution of adsorption process for manganese removal in water via agricultural waste adsorbents

Manganese has recently been a topic of interest among researchers, particularly when 1,752 million tonnes of manganese are expected to be produced by the steel industry in 2020. Manganese discharges from industrial effluents have increased manganese contamination in water sources. Its concentrations of more than 0.2 mg/L in the water sources could have negative impacts on human health and the aquatic ecosystem. Thereby, the available water treatment processes face challenges in effectively removing manganese at low cost. In response to these challenges, adsorption has emerged as one of the most practical water treatment processes for manganese removal. In particular, agricultural waste adsorbents received a lot of attention owing to their low cost and high efficiency (99%) in the removal of manganese. Therefore, this paper reviews the removal of manganese by adsorption process using agricultural waste adsorbents. The factors affecting the adsorption process, the mechanisms, and the performances of the adsorbents are elucidated in detail.

Management of water quality targets based on river-lake water quality response relationships for lake basins - A case study of Dianchi Lake

In a lake basin, there is a mismatch between river and lake water quality targets and a method for setting specific water quality targets for these rivers is urgently needed. Using Dianchi Lake as an example, we proposed a lake basin water quality management system based on the river-lake water quality response relationship, coupled with a Soil and Water Assessment Tool (SWAT) basin hydrological model and Environmental Fluid Dynamics Code (EFDC) lake water quality hydrodynamic model. River water quality control requirements based on the river-lake water quality response were proposed, under the premise that the Dianchi Lake water quality reaches the required standard. Then, water quality control targets for rivers were determined, and corrected for influencing factors, such as current river water quality and composition of flow. Our systematic approach efficiently identified key lake basin pollution sources, and accurately located key points for water quality improvement and pollution control. Combined with a correction for clean water source and current water quality of each river, the proposed water quality targets were practical and operable. Meanwhile, the EFDC model was used to verify the entire process to ensure that river water quality targets could be set to achieve lake water quality targets. To ensure that Dianchi Lake water quality can reach Class IV standard, the Chemical oxygen demand (COD) concentration would need to be maintained under 30 mg/L,Waihai total nitrogen (TN) below 7 mg/L, total phosphorus (TP) below 0.2 mg/L, and ammonia nitrogen (NH₃-N) below 2 mg/L.

Construction of the hydrological condition-persistent organic pollutants relationship in the Yangtze River Estuary

With anthropogenic activities, the persistent organic pollutants (POPs) accumulated in estuary has been notably concern but the influences of complex hydrodynamic conditions on the fate of POPs in estuary have not fully understood. In this study, the bottom velocity and the concentration of suspended sediment in the Yangtze River Estuary (YRE) were determined using the Acoustic Doppler Current Profiler (ADCP), while the concentration of three typical POPs with distinguishing properties, including polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and organichlorine pesticides (OCPs), were determined simultaneously. Then three nonlinear equations were determined for identifying the hotspots of PCBs, OCPs and PAHs in the YRE. The results indicated the goodness-of-fitting of these three equations were satisfactory, indicating the bottom velocity and the suspended sediment level could be used as the reference factor of POPs. For the YRE, the north branch, the upstream of the north branch, and the mouth of the YRE are identified as the hotspots of PCBs, PAHs and OCPs, especially in the normal, flood and dry season, respectively. Simple structure and easy data availability make the results and methods presented in this paper to be easily used as a reference for POPs studies in other regions.

Modeling Approach for Water-Quality Management to Control Pollution Concentration: A Case Study of Ravi River, Punjab, Pakistan

One of the challenging problems of Punjab, the most populous province of Pakistan, is the surface water-quality problem of the Ravi River, which flows through the main cities of the province. At present, the overall status of water quality is very polluted, primarily due to residential and industrial wastewater directly discharged into the Ravi River through a network of drains. Due to the poor quality of the water, the river ecosystem is not favorable for the aquatic and surrounding environment. Hence, management options are proposed to reduce pollution. Therefore, the study was formulated to identify the main sources of pollution along the Ravi River and their potential impact on the course of the river channel. In addition, the study applied a numerical model WASP 8.1 (Water Quality Simulation Program) to discover the best strategy for the improvement of water quality. Through the model simulation it was found that, if the flow at headwater and link canals is increased up to 50%, along with 75% improvement in the pollution concentration of drains through wastewater-treatment facilities, the water quality of the Ravi River can be improved up to an acceptable limit of water-quality standards.

Urban River Reserve Potentials as Passive Cooling Strategies

In Malaysia, urban riparian refers to river reserve that reflects green space. As surviving greenery space amidst concrete jungle, urban riparian is essential for safe-keeping the river health, the surrounding environment, and the well-being of urbanites. The existing developments found by the Malaysian riversides are already in place prior to river reserves establishment, thus constricting expansion and synchronisation due to its guidelines applied in isolation within several related agencies. Prior studies have highlighted the potential of riparian vegetation as a viable method that lowers the temperature within urban space. Hence, this paper probes into the potential of river reserve as a passive cooling strategy by determining the vegetation technical requirements from the light of urban river physical planning and design guidelines in Malaysia. Thus, this study outlines the possibility of integration by comparing vegetation requirements for river buffer with vegetation function and ability in altering radiation, as well as heat transfer, through physical attributes. By focusing on vegetation physical structure, the riparian area can attain multiple functions and benefits. Thus, this finding serves as a basis for integration of passive cooling strategies with vegetation requirements for urban river reserve, and for further studies that investigate other essential physical attributes.