Removal of natural organic matter in a typical south-China source water during enhanced coagulation with IPF-PACl

Systematic investigation on enhancing removal of natural organic matter （NOM） using inorganic polymer flocculant （IPF）, polyaluminum chloride（PACI） and polyacrylamide（PAM） was performed in a typical south-China source water. Enhanced coagulation and applying polymer flocculant-aid were compared through jar tests and pilot tests. Raw water and settled water were characterized and fractionated by resin adsorption. The results show that DOC composes major part of TOC. The DOC distribution keeps relatively stable all around the year with typical high amounts of the hydrophilic matter around 50%. The distribution between HoB, HoA and HoN varies and undergoes fluctuation with the year round. During the summer season, the HoN becomes gradually the major part in hydrophobic parts. PACI with the species being tailor-made shows little pH effect during coagulation. The enhanced coagulation dosage for PACI could be 4.5 mg/L for the typical source water. The highest TOC removal achieved 31%. To be economically, 3 mg/L dose is the optimum dosage. Although hydrophilic fractions of NOM of both treatment strategies are removed about 30%, NOM causing UV254 absorbance were well removed（about 90%）. Hydrophobic bases and acids fractions are much more removed under enhanced conditions. The hydrophilic fraction could be better removed using PAM, the polymer coagulant aid.

Disinfection byproduct precursor removal by enhanced coagulation and their distribution in chemical fractions

Raw water from the Songhua River was treated by four types of coagulants, ferric chloride （FeC13）, aluminum sulfate （A12（504）3）, polyaluminum chloride （PACl） and composite polyaluminum （HPAC）, in order to remove dissolved organic matter （DOM）. Considering the disinfection byproduct （DBP） precursor treatability, DOM was divided into five chemical fractions based on resin adsorption. Trihalomethane formation potential （THMFP） and haloacetic acid formation potential （HAAFP） were measured for each fraction. The results showed that hydrophobic acids （HoA）, hydrophilic matter （HIM） and hydrophobic neutral （HoN） were the dominant fractions. Although both HoN and HoA were the main THM precursors, the contribution for THMFP changed after coagulation. Additionally, HoA and HiM were the main HAA precursors, while the contribution of HoN to HAAFP significantly increased after coagulation. HoM was more easily removed than HiM, no matter which coagulant was used, especially under enhanced coagulation conditions. DOC removal was highest for enhanced coagulation using FeCl3 while DBPFP was lowest using PAC1. This could indicate that not all DOC fractions contained the precursors of DBPs. Reduction of THMFP and HAAFP by PAC1 under enhanced coagulation could reach 51% and 59% respectively.

pH modeling for maximum dissolved organic matter removal by enhanced coagulation

Correlations between raw water characteristics and pH after enhanced coagulation to maximize dissolved organic matter（DOM） removal using four typical coagulants（FeCl3,Al2（SO4）3,polyaluminum chloride（PACl） and high performance polyaluminum chloride（HPAC）） without pH control were investigated.These correlations were analyzed on the basis of the raw water quality and the chemical and physical fractionations of DOM of thirteen Chinese source waters over three seasons.It was found that the final pH after enhanced coagulation for each of the four coagulants was in？uenced by the content of removable DOM（i.e.hydrophobic and higher apparent molecular weight（AMW） DOM）,the alkalinity and the initial pH of raw water.A set of feed-forward semi-empirical models relating the final pH after enhanced coagulation for each of the four coagulants with the raw water characteristics were developed and optimized based on correlation analysis.The established models were preliminarily validated for prediction purposes,and it was found that the deviation between the predicted data and actual data was low.This result demonstrated the potential for the application of these models in practical operation of drinking water treatment plants.

Virus Removal by Iron Coagulation Processes

Waterborne viruses account for 30% to 40% of infectious diarrhea, and some viruses could persevere for some months in nature and move up to 100 m in groundwater. Using filtration setups, coagulation could lessen virus charges as an efficient pre-treatment for reducing viruses. This work discusses the present-day studies on virus mitigation using coagulation in its three versions i.e., chemical coagulation (CC), enhanced coagulation, and electrocoagulation (EC), and debates the new results of virus demobilization. The complexity of viruses as bioparticles and the process of virus demobilization should be adopted, even if the contribution of permeability in virus sorption and aggregation needs to be clarified. The information about virion permeability has been evaluated by interpreting empirical electrophoretic mobility (EM). No practical measures of virion permeability exist, a clear link between permeability and virion composition and morphology has not been advanced, and the direct influence of inner virion structures on surface charge or sorption has yet to be conclusively demonstrated. CC setups utilizing zero-valent or ferrous iron could be killed by iron oxidation, possibly using EC and electrooxidation (EO) methods. The oxidants evolution in the iron oxidation method has depicted promising findings in demobilizing bacteriophage MS2, even if follow-up investigations employing an elution method are needed to secure that bacteriophage elimination is related to demobilization rather than sorption. As a perspective, we could be apt to anticipate virus conduct and determine new bacteriophage surrogates following subtle aspects such as protein structures or genome size and conformation. The present discussion’s advantages would extend far beyond an application in CC—from filtration setups to demobilization by nanoparticles to modeling virus fate and persistence in nature.

FLOCCULATION/COAGULATION OF NATURAL ORGANIC MATTER FOR PRETREATMENT OF WATER ANDWASTE WATER

Characterization of water, waste water and natural organic matter are involved in this paper, and as well as the features of flocculation and coagulation for removing natural organic matter from water and waste water Novel flocculant and coagualant is strongly asked for improving removal efficiency and environment friendly. Enhanced coagulation is introduced to meet the experimental and practical requirement.

Comparative study on combined preoxidation by potassium permanganate composites with chlorine and preozonation for enhancing coagulation

Comparative pilot tests were conducted to investigate the coagulation-aid effects of the combined preoxidation by potassium permanganate composites （PPC） with chlorine and preozonation. And the synergistie mechanism of combined preoxidation was discussed. Results showed that 1.0 mg/L PPC with 2. 0 mg/L chlorine could further improve the quality of treated water, as indicated by residual turbidity, TOC and algae. The enhanced efficiency could be explained by the synergistic effect of the preoxidants themselves, or the effect of chlorine and the intermediate such as hydrous manganese dioxide, which was generated by potassium permanga- nate, the main ingredient of PPC.

The Application of KMnO_4 Pre-oxidation in Emergency Treatment of High-algae Source Water

Mobile emergency pilot water plant was used to carry out pilot study of KMnO4 pre-oxidation enhanced coagulation treating high-algae source water. Research showed that the optimal dosages of coagulant and KMnO4 in the process were 6 and 0. 4- 0. 6 mg / L respectively. Under the dosage,removal rate of water turbidity after precipitation rose by 11% than simple coagulation,and removal rate of algae rose by 15%. Removal rates of total amount of odor and GSM by the process were respectively 73% and 59%. The removal rate of total amount of algae by KMnO4 preoxidation was 40%,and removal effect of THM precursors was obvious.

Effects of Ca(OH)_2 assisted aluminum sulfate coagulation on the removal of humic acid and the formation potentials of tri-halomethanes and haloacetic acids in chlorination

The effects of addition of calcium hydroxide on aluminum sulphate （or alum） coagulation for removal of natural organic matter （NOM） and its subsequent effect on the formation potentials of two major types of regulated disinfection byproducts （DBPs）, haloacetic acids （HAAs） and trihalomethanes （THMs）, have been examined. The results revealed several noteworthy phenomena. At the optimal coagulation pH （i.e. 6）, the coagulation behavior of NOM water solutions versus alum dose, showed large variation and a consequent great change in the formation potentials of the DBPs at certain coagulant doses. However, with addition of a relatively small amount of Ca（OH）2, although the zeta potential of coagulated floes remained almost the same, NOM removal became more consistent with alum dose. Importantly, also the detrimental effect of charge reversal on NOM removal at the low coagulant dose disappeared. This resulted in a steady decrease in the formation potentials of DBPs as a function of the coagulant dose. Moreover, the addition of Ca（OH）2 broadened the pH range of alum coagulation and promoted further reduction of the formation potentials of the DBPs. The enhancement effects of Ca（OH）2 assisted alum coagulation are especially pronounced at pH 7 and 8. Finally, synchronous fluorescence spectra showed that the reduction in DBPs formation potential by Ca（OH）2-assisted alum coagulation was connected to an enhanced removal of small hydrophobic and hydrophilic HA molecules. Ca（OH）2-assistance of alum coagulation appeared to increase substantially the removal of the hydrophilic HA fraction responsible for HAAs formation, prompting further reduction of HAA formation potentials.