Pilot-Scale Microsand-Ballasted Flocculation of Wastewater: Turbidity Removal, Parameters Optimization, and Mechanism Analysis

The flocs formed during microsand-ballasted flocculation (MBF) have attracted much attention. However, few studies have reported on comprehensive process parameters of MBF and its mechanism is still not well understood. Jar test and pilot-scale continuous experiments were here conducted on two kinds of simulated wastewater, labeled S1 (21.6-25.9 NTU) and S2 (96-105 NTU). Results revealed the hydraulic retention time ratio in the coagulation cell, injection & maturation cell, lamella settler of pilot-scale MBF equipment was 1: 3: 7.3. The optimum poly aluminum chloride doses for Samples S1 and S2 were 0.875 g/L and 1.0 g/L. Besides, the optimum size of microsand was 49-106 µm and the optimum dose was 1.0 g/L. Under aforementioned conditions, the effluent turbidity of S1 was below 0.47 NTU, lower than the Chinese drinking water standard; that of S2 was below 1.7 NTU, meeting the Chinese recycled water standard. Turbidity removal ranged from 98.0% to 98.8% for S1 and 98.5% to 99.5% for S2 when microsand was added. Therefore, microsand addition enhances MBF performance, where microsand serves as an initial core particle. Some microsand core particles bond together to form a dense core structure of micro-flocs by the adsorption bridging of inorganic polymeric flocculant. Moreover, the size of the largest micro-flocs may be controllable as long as the effective energy dissipation ɛ0 is adjusted appropriately through specific stirring speeds. This work provides comprehensive pilot-scale process parameters for using MBF to effectively treat wastewater and offers a clearer explanation of the formation mechanism of microsand-ballasted flocs.

Lead Solubility in the Kırklareli Stream, Turkey

The research was conducted in the Kırklareli stream, which flows southwest through the city of the same name toward the village of Kavaklı. The aim of the study is to evaluate water analysis results and assess the potential that the European Union drinking water standard for lead can be achieved in the Kırklareli stream by reliance on the low solubility of lead phosphate minerals. The present study used Visual MINTEQ 3.1 for all water chemistry simulations. The European Union drinking water standard for lead, which is 10 μg L−1, is exceeded at least once and as many as three times at seven of the ten sites during the 2018 sampling season. Although the database solubility of hydroxypyromorphite is exceeded in most samples, it appears this may be the result of major ion substitutions in the hydroxypromorphite that forms in the Kırklareli stream which increases the effective solubility of lead in the stream.

Optimisation of degreemont water treatment package on Kedung Halang water treatment plant, Bogor, West Java

To provide drinking water in Bogor Regency, PDAM Tirta Kahuripan has several Water Treatment Plants (WTP) Kedung Halang WTP. Kedung Halang WTP consists of two water treatment packages, Indisi and Degreemont, with an average production of 37.3 L/s and 83.9 L/s, respectively. The purposes of this research are to evaluate the performance of the operating unit and process on the Degreemont Package and to provide optimisation recommendations based on the evaluation result. Steps in this research include evaluating the existing condition, providing recommendations, and analysing the quality of water produced. The evaluation found that one of the parameters did not fulfil the design criteria: the G.Td value on coagulation. The evaluation result of maximum flow rate is 125 L/s on intake, 150 L/s on coagulation, 130 L/s on flocculation and sedimentation, and 200 L/s on filtration. Thus, the optimum flow rate that can be operated is 125 L/s. The turbidity of the water produced has met the drinking water standard according to Minister of Health Regulation No. 492 of 2010, with removal efficiency above 95%. According to the result, it can be said that Degreemont Package is qualified to be applied as a drinking water treatment.

Relating Land Use/Cover and Landscape Pattern to the Water Quality under the Simulation of SWAT in a Reservoir Basin, Southeast China

Understanding the relationship between land use/cover pattern and water quality could provide guidelines for non-point source pollution and facilitate sustainable development. The previous studies mainly relate the land use/cover of the entire region to the water quality at the monitoring sites, but the water quality at monitoring sites did not totally reflect the water environment of the entire basin. In this study, the land use/cover was monitored on Google Earth Engine in Tang-Pu Reservoir basin, China. In order to reflect the water quality of the whole study area, the spatial distribution of the determinants for water quality there, i.e., the total nitrogen and total phosphorus (TN&TP), were simulated by the Soil and Water Assessment Tool (SWAT). The redundancy analysis explored the correlations between land use/cover pattern and simulated TN&TP. The results showed that: (1) From 2009 to 2019, forest was the dominant land cover, and there was little land use/cover change. The landscape fragmentation increased, and the connectivity decreased. (2) About 25% TP concentrations and nearly all the TN concentrations at the monitoring points did not reach drinking water standard, which means nitrogen and phosphorus pollution were the most serious problems. The highest output per unit TN&TP simulated by SWAT were 44.50 kg/hm2 and 9.51 kg/hm2 and occurred in areas with highly fragile landscape patterns. (3) TN&TP correlated positively with cultivated and construction land but negatively with forest. The correlation between forest and TN&TP summited at 500–700-m buffer and construction land at 100-m buffer. As the buffer size increased, the correlation between the cultivated land, and the TN weakened, while the correlation with the TP increased. TN&TP correlated positively with the Shannon’s Diversity Index and negatively with the Contagion Index. This study provides a new perspective for exporting the impact of land use/cover pattern on water quality.

Water Quality Assessment of Paper Mills Effluent Discharge Areas

The study attempted to assess the water quality around paper mill effluents discharge areas. Several physicochemical parameters and the Canadian Council of Ministers of the Environment (CCME) Water Quality Index (WQI) were considered to determine the pollution level of surface and groundwater in the selected paper mills areas located in Saidpur, Gobindaganj, and Dupchanchia Upazilas of Bangladesh. Physicochemical characterization of the surface water around the paper mills areas showed that the concentration of EC, TSS, BOD5, COD, phenols, NO3−-N, and K+were exceeded the surface water standard, whereas the DO level ranged from 1.63 to 3.5 were found below the Environmental Conservation Rules (ECR), 1997 standard. Besides, the BOD, COD, and Mn ion concentrations of groundwater exceeded the drinking water standard. In most sampling sites, the WQI of the surface water showed ‘marginal’ category, and the groundwater quality showed 'fair' category. The study observed that the toxic effluents discharged from the paper mills caused harm to the aquatic ecosystem.

Removing Ammonium From Contaminated Water Using Purolite C100E: Batch, Column, and Household Filter Studies

Ammonium removal from drinking water to protect human and environmental health is one of the major global concerns. This study evaluates the performance of Purolite C100E, a commercial cation exchange resin, on eliminating ammonium in synthetic and real contaminated groundwater. The results demonstrate that the pH operation range of the resin for better ammonium removal is 3 to 8, while the optimum contact time was about 30 min. The kinetics of the ammonium removal process followed both the Pseudo-first order and Pseudo-second order models. Equilibrium data of ammonium removal fitted both the Langmuir and Freundlich isotherm models with the maximum Langmuir ion exchange capacities for initial ammonium concentrations of 10-200 mg/L and 50-2000 mg/L reaching 18.37 mg/g and 40.16 mg/g, respectively. The presence of co-ions in the water reduced the ammonium removal efficiencies in the order Mg2+> Ca2+> K+. The maximum exchange capacity in the fluidised bed studies of the original Purolite C100E (bed height 27 cm, resin weight 75 g, initial ammonium concentration 17.4 mg/L, filtration velocity 0.5 m/h) was 10.48 mg/g. It progressively reduced slightly after three regeneration cycles to 8.79 mg/g. The column breakthrough data satisfactorily fitted the Thomas model. A household filter cartridge packed with 4 kg Purolite C100E (80 cm height) and operated at a filtration velocity of 1.9 m/h in Vietnam successfully reduced the initial 6 mg NH4+/L in groundwater (after sand filter pre-treatment) to well below the Vietnam drinking water standard (3 mg/L) continuously for one week.

Drinking water quality assessment from water dispensers in an educational institution

Water dispensers are commonly used in educational institutions in developing countries. Assessment of factors influencing drinking water quality from this source is important due to its potential to cause waterborne diseases and other health risks. This study aimed to assess microbial contamination and the factors affecting drinking water quality from water dispensers at Walailak University, Southern Thailand. Drinking water samples from 60 water dispensers of different type brands were collected and tested for physicochemical and microbiological parameters by following WHO Drinking Water Quality guidelines. Also evaluated by questionnaires were hygienic standards and maintenance of water dispensers. The physicochemical analysis of all water samples did not exceed the reference values of the drinking water standard; the hardness value in only 13.3% of samples was slightly higher than the reference limit. The microbiological results indicated that total coliform and fecal coliform bacteria were found in 16.67% and 8.33% of total samples, respectively. Escherichia coli was not detected in any of the water samples. The assessment of factors influencing drinking water quality, location and pathogen source around water dispensers, hygienic environment, maintenance of water dispensers had a significant effect on drinking water quality.

Arsenic in Petroleum-Contaminated Groundwater near Bemidji, Minnesota Is Predicted to Persist for Centuries

We used a reactive transport model to investigate the cycling of geogenic arsenic (As) in a petroleum-contaminated aquifer. We simulated As mobilization and sequestration using surface complexation reactions with Fe(OH)3 during petroleum biodegradation coupled with Fe-reduction. Model results predict that dissolved As in the plume will exceed the U.S. and EU 10 µg/L drinking water standard for ~400 years. Non-volatile dissolved organic carbon (NVDOC) in the model promotes As mobilization by exerting oxygen demand, which maintains anoxic conditions in the aquifer. After NVDOC degrades, As re-associates with Fe(OH)3 as oxygenated conditions are re-established. Over the 400-year simulation, As transport resembles a “roll front” in which: (1) arsenic sorbed to Fe(OH)3 is released during Fe-reduction coupled to petroleum biodegradation; (2) dissolved As resorbs to Fe(OH)3 at the plume’s leading edge; and (3) over time, the plume expands, and resorbed As is re-released into groundwater. This “roll front” behavior underscores the transience of sorption as an As attenuation mechanism. Over the plume’s lifespan, simulations suggest that As will contaminate more groundwater than benzene from the oil spill. At its maximum, the model simulates that ~5.7× more groundwater will be contaminated by As than benzene, suggesting that As could pose a greater long-term water quality threat than benzene in this petroleum-contaminated aquifer.

Integration of Iron Coagulant, Copperas and Calcium Hydroxide for Low-Cost Groundwater Treatment in Kelantan, Malaysia

In Kelantan, more than 70 % of domestic water is supplied by groundwater sources. These water sources are commonly contaminated and do not meet the World Health Organization (WHO) drinking water standard and the Malaysian Ministry of Health (MMOH). This research's main objective is to study the performance of iron-based coagulants Ferrous Sulphate on its optimum dosage, formulation, and concentration. Series of jar tests are conducted by adding and comparing five different copperas solution concentrations from 15 % to 0.6 % into the 500 mL beaker. The prepared copperas solutions are combined with lime (calcium hydroxide), and the performance of with (copperas plus) and without lime are compared. The results obtained show that copperas plus has a far better performance compared to copperas solution. The copperas plus results comply with the drinking water standard for pH value (6.5-8.5) and turbidity (below 5 NTU). Copperas and turbidity removal efficiency are between 89% and 99%, while copperas has a lower range of turbidity removal efficiency, 72.9 % and 97.7 %. Most of the results obtained do not comply with the drinking water standard of iron (Fe) and Manganese (Mn) over 0.3 and 0.1 mg/L, respectively. However, the potential of copperas and copperas plus to treat domestic drinking water could be improvised by further studying its dosing effect on heavy metal content.

Study on the Effect of Applied Pressure on Iron and Manganese Rejection by Polyamide and Polypiperazine Amide Nanofiltration Membranes

The aim of this research is to investigate the removal behavior of iron and manganese that naturally exist as divalent ions in groundwater by using nanofiltration membranes. The main focus of this study is to better understand the effect of applied pressures during the rejection of these metallic ions from synthetic groundwater in order to achieve drinking water standard. Polyamide and polypiperazine amide nanofiltration membranes denoted as PA-NF and PPA-NF were selected to investigate the iron and manganese rejection at low applied pressures (1-5 bar). In single solute solution with feed concentration at 10 mg/L and initial pH of 6.8 ± 0.5, the rejection of iron was ≥96% by PA-NF membrane at applied pressure of 2 bar. However, the rejection percentage by PPA-NF was 86.6% whereby this membrane unable to remove iron to the allowable drinking water standard. The rejection of manganese with single solute at concentration of 1 mg/L with initial pH of 6.8 ± 0.5 by using the PA-NF membrane was ≥98% and almost all of dissolved manganese were rejected at 5 bar. However, manganese removal by PPA-NF membrane was found less than 70% for all of the applied pressures. Findings from this work showed that the removal of iron and manganese were dependent on the applied pressures. PA-NF membrane able to remove both metallic ions that comply with the drinking water standard. The increased of applied pressure contributed to concentration polarization effect on the membrane surfaces leading to a decrease in solute rejection by decreasing the charge effect mainly for the iron removal from synthetic groundwater.