Assessing the risk posed by high-turbidity water to water supplies

High turbidity in raw water poses a major challenge to drinking water quality and requires effective, sustainable treatment solutions. This work investigates the reduction in turbidity in raw water and the enhancement of overall drinking water quality through the coagulation–flocculation process. The performance of Pine cone extract as a bio-coagulant was evaluated using four different solvent-based extractions (PC-H2O, PC-HCl, PC-NaCl, and PC-NaOH). The effects of key operational parameters were analyzed, and jar tests were carried out to enhance the coagulation–flocculation process by identifying the optimal conditions. Experimental design was further refined using RSM based on a BBD, incorporating three factors: initial pH, coagulant dosage, and settling time, with turbidity removal efficiency as the response variable. Statistical analysis confirmed that initial pH, coagulant dosage, and settling time significantly influenced turbidity reduction at a confidence level of p-value < 0.05 for all four solvents. Among the extracts tested, PC-HCl demonstrated the highest turbidity removal efficiency. The optimal conditions achieving 78.57% turbidity reduction were a pH of 8.5, a coagulant dosage of 100 mL/L, and a settling time of 120 min. These findings highlight the significant potential of Pine cone extract as an effective, sustainable, and eco-friendly organic coagulant for raw water treatment.

Global population increases specially in developing countries such Iraq requires more effort and investment in water and sanitation facilities to enhance the welfare of people in meeting the MDG objectives. The competition for water resources coupled with the generation of wastewater is creates additional pressure on the available supplies and increasing pollution level. To address such challenges it has become necessary to build new or enhance existing treatment systems. In different part of Iraq including in Samarra City effort is being made to enhance the water quality in regard to its physical, chemical, and biological characteristics as well as the minerals and organic substances which may produce adverse physiological effects. In order to evaluate different aspect of water quality this study focused on evaluating the drinking water quality and also the performance of the two treatment plants in Samarra City located on the left bank of Tigris River to the north of Baghdad City. The investigation covered the period of December, 2004 to May, 2005. The first is the main conventional water treatment plant with a capacity of 2400m3/hr. and the second is a compact unit with a capacity of 200m3/hr. The collected water data cover some of the important physical and chemical parameters of water quality; covering temperature, TDS, turbidity, pH and residual chlorine. While the bacteriological parameters covered total plate count (TPC) and E-coli for stages of treatment plants. The results show that turbidity of raw water is not high (3.84-425) NTU compared with Al-Karkh water project in Baghdad City (6-1400) NTU, because the intakes of WTPs are located in the downstream of Samarra barrage which serves as a pre-sedimentation tank. Low clarifiers turbidity removal efficiencies of (48.323 %) and (32.09 %) were obtained for treatment plant and compact unit respectively, while for filters removal efficiencies were (63.2 %) and (39.05 %) respectively. The monthly average turbidity of supplied water for conventional water treatment plant and compact unit were (4.3 and 18.2) NTU, the percent of violation to Iraqi Specifications were (29.4 % and 64.7%) respectively. Not always, increasing in raw water turbidity result in an increase in turbidity removal efficiency. pH values and TDS concentrations of supplied water are within Iraqi, EPA and WHO Specifications. Low amount and interrupted chlorination in WTP and CU, so, irregular chlorination results in frequent outbreak of waterborne diseases. It can be recommend to improve the water quality monitoring program through the application of; coagulant aids to overcome the high turbidity of raw water during the rainy season, the hexagonal tube settler in the sedimentation tank of the compact unit to get the designed SOR and anthracite with sand as a dual porous media to increase the filtration rate to overcome the shortage in hot seasons. Also periodic systematic maintenance for different units of treatment plants is required.

The physical efficiency of a number of coagulants alum, ferrous sulfate and ferric chloride in addition to coagulation organic aids like poly ethylene glycol (PEG), polyacrylamide (PAM) and non-organic like Bentonite in removing turbidity of raw water in its high and low turbidity 850 NTU, 52 NTU respectively was studied. The optimal dose was determined for each of them that give less turbidity and higher removal percentage. The results declared that alum was the best removal for both high and low turbidity which reach 99.59% and 97.54% respectively. Ferrous sulfate, Ferric chloride, and calcium oxide were the best for removing turbidity of high turbid raw water 98.26, 98.66 and 92.18% respectively. For coagulation aids, the best of them was (PAM) for both raw water turbidity, while (PEG) record good removal percentage for low turbidity that reach 89.81%. Bentonite give lowest removal percentage for low turbidity 31.92%, on contrast with high turbidity 74%. used of Bentonite with alum improved the removal to 88.92%.

After the genocide of 1994, Rwanda has been struggling to contain urban migration and its pressures on existing facilities. Water supply coverage is low at 76% in urban areas and 68% in rural areas. This implies that huge investments are required to meet the Millennium Development Goals on water supply and sanitation. This study was conducted to assess the existing problems of raw water intake systems at Yanze and Nyabarongo intakes in Kigali; Shyogwe intake in Ruhango District; and Kadahokwa intake in Huye District. The study was in response to high amounts of sediments in raw water which literally clogged the intake systems for a number of days, resulting in erratic water supplies to the residents in the rainy season. The study focused on performance problems of the intake systems, raw water turbidity variations and the assessment of how environmental concerns could be addressed in the design of intake systems in areas of high soil erosion activities. Data was collected through interviews and physical measurements. The study revealed that flooding, intake site selection, erosion, screen clogging, intake protection, high raw water turbidity, inadequacy of raw water supplied to the water treatment plants, and low downstream environmental flows were the main intake problems. The Yanze intake had worst problems with high levels of flooding, erosion, sedimentation, and high raw water turbidity levels. The bank filtration system at Nyabarongo gave the least problems of raw water turbidity. Yanze and Nyabugogo river intakes systems were found to be threatened by decreasing water levels attributed to surrounding upstream landuse activities. It was recommended that proper maintenance of existing structures, landuse management around river intakes, use of well-designed reservoir abstraction systems, increased groundwater abstraction systems (including bank filtration), would greatly improve the performance of intake systems in Rwanda.

The extent to which drinking water turbidity measurements indicate the risk of gastrointestinal illness is not well understood. Despite major advances in drinking water treatment and delivery, infectious disease can still be transmitted through drinking water in the United States, and it is important to have reliable indicators of microbial water quality to inform public health decisions. The objective of our study was to assess the relationship between gastrointestinal illness, quantified through emergency department visits, and drinking water quality, quantified as raw water and filtered water turbidity measured at the treatment plant. We examined the relationship between turbidity levels of raw and filtered surface water measured at eight major drinking water treatment plants in the metropolitan area of Atlanta, Georgia, and over 240,000 emergency department visits for gastrointestinal illness during 1993-2004 among the population served by these plants. We fit Poisson time-series statistical regression models that included turbidity in a 21-day distributed lag and that controlled for meteorological factors and long-term time trends. For filtered water turbidity, the results were consistent with no association with emergency department visits for gastrointestinal illness. We observed a modest association between raw water turbidity and emergency department visits for gastrointestinal illness. Our results suggest that source water quality may contribute modestly to endemic gastrointestinal illness in the study area. The association between turbidity and emergency department visits for gastrointestinal illness was only observed when raw water turbidity was considered; filtered water turbidity may not serve as a reliable indicator of modest pathogen risk at all treatment plants.

Two sets of input parameters were employed to develop Extreme Learning Machine Radial Basis Function (ELM-RBF) models predicting residual aluminum, in order to facilitate parametric analysis of reported physical and chemical phenomena relating to the effect of alum dosage, raw water (RW) turbidity and RW color on residual aluminum concentration. RW turbidity was identified as the dominant variable affecting the distribution of the multivariate data, condensed into two principal components using principal component analysis. Thus two sets of models were developed based on the RW turbidity value: low turbidity models and high turbidity models. The performance of all models was satisfactory, with test correlation coefficients exceeding 0.85. The shapes of the plots of the parametric analysis were satisfactory and were in line with reported phenomena. However, the numerical accuracy of the plots obtained by the parametric analysis was poor. It was noted that using data with a wider range of values for the dominant variable (RW turbidity) helped improve the parametric plots.

Ultrafiltration (UF) is a membrane separation process by which the particles of mechanical nature are removed from the water. Thanks to the pore diameter that are the order of tenths nm and the material, constructional and chemical properties of UF membranes, this technology represents the final solution for a secured protection against the turbidity that is caused by content of non-soluble and colloid particles of organic and inorganic origin, bacteria and the majority of viruses. Ultrafiltration was investigated within the pilot-plant tests at the WTP Jasná during the treatment of surface water originating from the water source Zadná voda. Water treatment is in this locality focused on turbidity that is caused by storm rainfalls and snow thawing. Fully automated ultrafiltration equipment with the membrane modul UA-640 (Microdyn-Nadir) was used. On the base of filtration cycles, the effectiveness of membraned technology was evaluated. Water was supplied to the UF-device by the pump, so the UF-flow rate was invariably maintained at the 600 L/h Period of filtration cycle was 30 minutes. Following the end of the cycle, washing of membrane by using the back-flushing by water and air was applied. Filtered water accumulated in the tank was used for back-flushing while the air was supplied by the air-pump connected to the device. Any way of washing of the membrane did last for 30 seconds. On the base of filtration cycles, the effectiveness of membraned technology was evaluated. Turbidity removal is the major issue at the WTP Jasná. Limit for turbidity 5 NTU is set by Decree No. 247/2007 Col. Measuring data provided that the turbidity level of water treated by using the ultrafiltration device are compliant with the legal limit for drinking water. By using the ultrafiltration, the decrease by 76,1% has been reached in the first experiment (average turbidity in raw water 1,55 NTU). The efficiency of turbidity removal was 95,2% that was reached by ultrafiltration of water with a higher level of turbidity (average turbidity in raw water 8 NTU). High effectiveness of ultrafiltration was reached also with the water with the turbidity 37 NTU. In all of the three experiments, the turbidity of treated water ranged between 0,37 - 0,38 NTU.

Coagulation process is a most important part in the water treatment process. However, in the process of water treatment in water treatment plant Kandana, there is a problem on coagulation under higher and lower levels of turbidity using only Alum (Al2(SO4)3.14 H2O). This research study was conducted to improve coagulation process to increase the turbidity removal efficiency under higher (>80) and lower (<8) turbidity conditions. Therefore, the objectives of the study are, to study the proper coagulation process for low and very high turbidity levels in source water under the efficiency of Alum with anionic polymers (Polyacrylamide) and to study the efficiency of Alum with pre-lime (Calcium hydroxide) usage in the coagulation process. Water samples were collected from the intake when the turbidity level was high and low and sample size was 50 L per once. The average optimum Alum dose of the low turbidity levels was determined by conducting jar tests. Optimum Alum dose of the low turbidities was used to determine the optimum lime dose and the effective polymer adding method and the optimum polymer dose for the low turbidities. Chemical and physical parameters were tested for raw water samples and settled water samples. Above same procedure was conducted for the high turbidity samples. As conclusions, there was not a considerable difference of final turbidity among the addition of Alum only, addition of pre-lime with Alum and addition of polymer with Alum for low turbidity raw water. Therefore, adding polymer and pre-lime with Alum have not given an efficiency for the low turbidity raw water. According to the results of high turbidity raw waters there was a considerable difference of final turbidity among the addition of Alum only, addition of pre-lime and Alum and addition of polymer and Alum. Adding polymer and pre-lime with Alum is effective for high turbidity raw water. Adding polymers with Alum more effective than the adding pre-lime with Alum for high turbidity raw water. There was a considerable pH deference by lime and polymer coagulation in high turbidity raw water. Keywords: Turbidity, Raw water, Coagulation, Treatment, Jar test

In order to fulfil the high water demand in Banda Aceh City, the Lambaro Water Treatment Plant (WTP) has been operating above its designed capacity. The produced and distributed water quality is decreasing in term of turbidity, as well. It is indicated by some events that the distributed water exceeds the allowed limit. The additional burden is that due to rainy season and human activities at river upstream, the raw water turbidity is higher than expectation in several occasions. This study is conducted to evaluate the influence of production flow rate and raw water turbidity on distributed water turbidity. The data used in this study is acquired from the SCADA system with time range from January to May 2014.

High turbidity in water not only will reduce the quality of water itself but it can give impact to the ecosystem as well. In water treatment, coagulation and flocculation are the process involved in removing turbidity. Chemical coagulant such as aluminium sulfate (Alum) and ferric chloride are effective way and widely used in order to remove the turbidity in water. However, these chemical coagulants have a side effect in spite of the effectiveness in turbidity removal, the usage of alum and other chemical coagulants bring concerns due to its impact to the environment, human health and economy. Therefore, natural coagulant is another alternative for turbidity removal in water treatment. Natural coagulant is a plant-based coagulant which can be used to replace chemical coagulants. These coagulants are generally cheaper and safer than chemical counterparts. This research is conducted to compare the effectiveness of natural based coagulant made from Psophocarpus tetragonolobus and chemical coagulant in improving the quality of raw water. Findings from this study showed P. tetragonolobus can remove turbidity up to 60 percent with 40 ml, 1% solution. Therefore, P. tetragonolobus can be considered as a potential resource for natural coagulant.

The present study deals with the assessment of different physicochemical parameters (pH, electrical conductivity (E.C.), turbidity, total dissolved solids (TDS), and dissolved oxygen) in different surface water such as pond, river, and canal water in four different seasons, viz. March, June, September, and December 2023. The research endeavors to assess the impact of a cationic polyelectrolyte, specifically poly(diallyl dimethyl ammonium chloride) (PDADMAC), utilized as a coagulation aid in conjunction with lime for water treatment. Employing a conventional jar test apparatus, turbidity removal from diverse water samples is examined. Furthermore, the samples undergo characterization utilizing X-ray diffraction (XRD) and scanning electron microscopy (SEM) techniques. The study also conducts correlation analyses on various parameters such as electrical conductivity (EC), pH, total dissolved solids (TDS), turbidity of raw water, polyelectrolyte dosage, and percentage of turbidity removal across different water sources. Utilizing the Statistical Package for Social Science (SPSS) software, these analyses aim to establish robust relationships among initial turbidity, temperature, percentage of turbidity removal, dosage of coagulant aid, electrical conductivity, and total dissolved solids (TDS) in pond water, river water, and canal water. A strong positive correlation could be found between the percentage of turbidity removal and the value of initial turbidity of all surface water. However, a negative correlation could be observed between the polyelectrolyte dosage and raw water's turbidity. By elucidating these correlations, the study contributes to a deeper understanding of the effectiveness of PDADMAC and lime in water treatment processes across diverse environmental conditions. This research enhances our comprehension of surface water treatment methodologies and provides valuable insights for optimizing water treatment strategies to address the challenges posed by varying water sources and seasonal fluctuations.

In this study, direct-coupled water treatment facilities with the capacity of 500 ㎥/day were installed and operated in Indonesia and Cambodia, respectively. In Indonesia, raw water was taken from the reservoir, and the water treatment plant for the process consisting of UF-AOP-GAC-Chlorination was installed horizontally. In Cambodia, groundwater was used as raw water, and the water treatment plant for the process consisting of UF-GAC-Chlorination was installed vertically. All water treatment plants were operated stably, and the produced water was suitable for drinking in terms of water quality standards. In the detailed evaluation of the unit process, the TMP of the UF process was stable at 0.35 ~ 0.4 kgf/㎠ when the raw water was groundwater with low turbidity, and chemical cleaning was unnecessary during the operation period of about 10 months; Meanwhile, in Indonesia where the turbidity of raw water is relatively high, the TMP was varying between 0.4 ~ 1.0 kgf/㎠ and chemical cleaning was required once a month. In addition, the differential pressure of GAC adsorber was maintained at a low level of 0.1 kgf/㎠ or less. Also, the electricity consumption was evaluated to be in the range from 0.23 to 0.26 kWh/㎥ for the operation of the Indonesian plant and 0.176 kWh/㎥ in Cambodia. The electricity consumption was significantly affected by the increase of TMP due to the turbidity of raw water, and the operating pressure needed to be minimized.

The scope of the present study is the estimation of key operational parameters of a drinking water treatment plant (DWTP), particularly the dosages of treatment chemicals, using artificial neural networks (ANNs) based on measurable in situ data. The case study consists of the Aposelemis DWTP, where the plant operator had an estimation of the ANN output parameters for the required dosages of water treatment chemicals based on observed water quality and other operational parameters at the time. The estimated DWTP main operational parameters included residual ozone (O3) and dosages of the chemicals used: anionic polyelectrolyte (ANPE), poly-aluminum chloride hydroxide sulfate (PACl), and chlorine gas (Cl2(g)). Daily measurable results of water sample analysis and recordings from the DWTP Supervisory Control and Data Acquisition System (SCADA), covering a period of 38 months, were used as input parameters for the artificial neural network (1188 values for each of the 14 measurable parameters). These input parameters included: raw water supply (Q), raw water turbidity (T1), treated water turbidity (T2), treated water residual free chlorine (Cl2), treated water concentration of residual aluminum (Al), filtration bed inlet water turbidity (T3), daily difference in water height in reservoir (∆H), raw water pH (pH1), treated water pH (pH2), and daily consumption of DWTP electricity (El). Output/target parameters were: residual O3 after ozonation (O3), anionic polyelectrolyte (ANPE), poly-aluminum chloride hydroxide sulfate (PACl), and chlorine gas supply (Cl2(g)). A total of 304 different ANN models were tested, based on the best test performance (tperf) indicator. The one with the optimum performance indicator was selected. The scenario finally chosen was the one with 100 neural networks, 100 nodes, 42 hidden nodes, 10 inputs, and 4 outputs. This ANN model achieved excellent simulation results based on the best testing performance indicator, which suggests that ANNs are potentially useful tools for the prediction of a DWTP’s main operational parameters. Further research could explore the prediction of water chemicals used in a DWTP by using ANNs with a smaller number of operational parameters to ensure greater flexibility, without prohibitively reducing the reliability of the prediction model. This could prove useful in cases with a much higher sample size, given the data-demanding nature of ANNs.

A case study of dissolved air flotation for seasonal high turbidity water in Korea

Observations of blanket characteristics in full-scale floc blanket clarifiers