Coagulant Dosage Control Research Articles

Determination of cost-effective optimum coagulant dosage for removal of disinfection by-product precursors in water treatment based on the theory of elasticity

Determination of coagulant dosage in drinking water treatment is related to the requirements for drinking water quality as well as the treatment costs. Selection of appropriate coagulant dosages has been an issue for water treatment utilities, though empirical approaches were normally considered or employed. Inspired by the theory of elasticity in microeconomics, this study explored a novel approach for the cost-effective optimum coagulant dosage. This could enable water utilities to achieve the maximum possible removal efficiency of precursors for disinfection byproducts (DBPs) while maintain an economical dosage without incurring an excessive cost. The relationships between DBP formation potential (DBPFP) and several relevant water quality parameters were first examined and evaluated. UV254 was found the most appropriate DBPFP indicator with the highest correlation coefficients. Based on the relationship of UV254 and DBPFP, an approach for determination of cost-effective optimum coagulant dosage was delineated. The results showed that use of the cost-effective optimum coagulant dosage, which account for approximately 33% of optimum coagulant dosage, could achieve 79% of maximum removal efficiencies of UV254 for the source waters tested, thereby substantially reducing the formation of DBPs. Further increase the coagulant dosage was believed uneconomical since the increase in UV254 removal was limited. Similar results were obtained with different coagulants and with raw water samples with diverse water qualities. The results suggest that the proposed approach could provide a mathematical tool for cost-effective optimum coagulant dosage control which could at the same time achieve sufficient removal of natural organic matter to reduce DBPs formation.

Optimal Calculation Method of Mean Equivalent Diameter of Floc Particles Based on MCC

In the process of water treatment, coagulation is an important process to remove minerals and organic particles from raw water, which has typical time delay and nonlinearity. The effect of coagulation directly affects the turbidity of the effluent. According to the good correlation between the mean equivalent diameter of floc particles and the turbidity of effluent water, the image processing method is used to preprocess the floc image, the parameters of floc particles are quantitatively analyzed, and the mean equivalent diameter of floc particles is obtained, which is used as one of the bases for the control of coagulant dosage. However, no matter whether the coagulation process in actual situations interferes with the outside world or not, the equivalent diameters of floc particles after coagulation may have abnormal and invalid values, which may lead to a problem that there is a large difference between the mean equivalent diameter of floc particles calculated by a least square method and the mean valid equivalent diameter of floc particles. In response to this problem, this article proposes an optimal calculation method of the mean equivalent diameter of floc particles based on the maximum correntropy criterion (MCC) to reduce the negative impact of the abnormal and invalid equivalent diameters of floc particles on the mean equivalent diameter and provide an important reference data for the precise dosing control of coagulants. Finally, the feasibility of the theoretical results is verified by several numerical experiments.

Automatic control of coagulant dosage on the sedimentation and dissolved air flotation(SeDAF) process for enhanced phosphorus removal in sewage treatment facilities

Automatic control of coagulant dosage on the sedimentation and dissolved air flotation(SeDAF) process for enhanced phosphorus removal in sewage treatment facilities

Model-based measurement error detection of a coagulant dosage control system

Online instruments are widely used in wastewater treatment plants and drinking water treatment plants for process monitor and control. Although maintenances of online sensors are important routine works, potential measurement errors of online sensors are challenging not only monitoring of coagulation process but also the coagulant dosage control system, what this paper is focusing on. In order to estimate and detect the potential measurement errors, this paper proposes a concept of model-based measurement error detection. Relying on the model of the outlet software senor, the differences between simulations and measurements of outlet turbidity can be used as indicator of inlet measurement errors. Based on the concept, this paper enables to quantify the measurement errors and build up a novel detection method. In addition, the paper compares the proposed detection method with a traditional method—the normal variation range. The results show that the proposed method has a better efficiency to detect the measurement error.

SC response characteristics of two kinds of coagulant

Automatic coagulant dosage control with streaming current (SC) technique is introduced in this paper. Aluminum and ferric coagulants are widely used in surface water treatment. The SC response characteristics of P-AlCl3 aluminum coagulant and P-FeCl3 ferric coagulant were investigated in this work. Bench-scale water treatment results were obtained from jar tests including rapid mixing, flocculation and undisturbed sedimentation. Results showed that aluminum coagulant is more sensitive than ferric coagulant to SC response.

Verification of automatic coagulant dosage control technology based on aluminum concentration at a water purification plant

An automatic coagulant dosage control technology for water purification plants was developed to deal with rapid changes of feed water quality. Control logic was developed to decide coagulant dosage based on aluminum concentration in the mixing tanks. A coagulant-sedimentation process apparatus was installed in December 2010 in a water purification plant, and the coagulant dosage control test using feed water was started. The developed system was confirmed to be effective for managing settled water turbidity and adequacy of coagulant dosage. For actual changes of feed water quality at the water purification plant over more than one year, the developed system was able to maintain settled water turbidity at less than 1.0 mg-kaolin/L in the period of high feed-water turbidity.

Evaluation of the Streaming Current Detector (SCD) for Coagulation Control

A streaming current detector (SCD) is an instrument for measuring the charge that exists on small, suspended particles in water. The SCD is the instrument that can be used to measure coagulated particle stability for the feedback control of coagulant dosage. This report discusses the application of SCD as an instrument for coagulation dosage control. The SCD with automatic control of coagulant dosage consistently produced acceptable water quality, even during periods of changing raw water turbidity and varying flow rates. It minimizes under and overdosing of coagulant. It requires regular cleaning and maintenance to ensure optimum operation. The SCD is no substitute for efficient water treatment management.

Development of automatic coagulant dosage control technology for rapid change of raw water quality parameters

An automatic coagulant dosage control technology for water purification plants was developed to deal with rapid changes of raw water quality parameters. Control logic was developed to decide coagulant dosage based on aluminum concentration in rapid mixing tank water based on results of semi-pilot scale experiments. This logic enabled quick feedback on the excess or lack of coagulant. It was found that the aluminum residual rate, which was proposed as an indicator of coagulation reactions, could be given as a function of coagulant dosage and turbidity. The effectiveness of the control logic was verified in semi-pilot scale experiments. Settled water turbidity was within ±0.5 NTU of target value even when raw water turbidity increased rapidly up to 100 NTU.

Coagulation Behaviors and Coagulant Dosage Control of Kaolin and Bentonite Suspensions

Coagulation Behaviors and Coagulant Dosage Control of Kaolin and Bentonite Suspensions

Recent development of an in-situ image detecting system for floc characterization and monitoring

Coagulation control plays a significant role in the final yield of sludge volume during water and wastewater treatment. The precise control of coagulant dosage, floc formation and aggregation behaviour becomes the important target for the coagulation process both in water and wastewater treatment. A critical review is presented first in this paper on the recent advances in coagulation control. In particular, the development of an in-situ image detecting system (IDS) based on characterization of floc properties, involving average diameter, fractal dimension and apparent strength is discussed. The results show that the data obtained from the IDS are generally in accordance with the outcome of common coagulation experiment, and have sensitivity for the slow stirring rate, raw water turbidity and coagulant dosage, in different degrees. The combination of IDS and ANN model is also discussed. This provides a possibility for applying the proposed IDS to control the coagulation process in water and wastewater treatment.

Flocculation control study based on fractal theory

A study on flocculation control based on fractal theory was carried out. Optimization test of chemical coagulant dosage confirmed that the fractal dimension could reflect the flocculation degree and settling characteristics of aggregates and the good correlation with the turbidity of settled effluent. So that the fractal dimension can be used as the major parameter for flocculation system control and achieve self-acting adjustment of chemical coagulant dosage. The fractal dimension flocculation control system was used for further study carried out on the effects of various flocculation parameters, among which are the dependency relationship among aggregates fractal dimension, chemical coagulant dosage, and turbidity of settled effluent under the conditions of variable water quality and quantity. And basic experimental data were obtained for establishing the chemical coagulant dosage control model mainly based on aggregates fractal dimension.

Conductometric Control of Coagulant Dosage in Treatment Plants

coagulation of colloids in water, an attempt was made to use the conductometric technique to make rapid analyses of the rates of coagulation. The procedure was suggested by a paper by Babcock and Knowlton {1). In order to become acquainted with their techniques it was decided to try to duplicate the previous work. It was discovered that the results of the two sets of investigations were similar only in certain instances. The areas of dif-