AU2001265430A1 - Method for treatment of water containing humic matter for the production of drinking water with enhanced coagulation stage using inorganics polymers of al and activated S102 - Google Patents

Abstract

The invention relates to a method of removal of humic matter from natural water to drinking water quality standards in which inorganic polymers of Al and activated SiO2 in a controlled pH range are used in a coagulation step. With this method maximum effects of reduction of humic water with minimum consumption of the chemicals and extremely low content of residual Al in drinking water is obtained.

Description

METHOD FOR TREATMENT OF WATER CONTAINING HUMIC MATTER FOR

DRINKING WATER, WITH ENHANCED COAGULATION STAGE USING INORGANICS POLYMERS OF AL AND ACTIVATED SIO2 IN CONTROLED pH

RANGE

a) Field of technique to which inovation belong

This inovation belong to the field of water treatment, closer, to the field of drinking water treatment, and refers to the method for removal humic matters from natural water which present most wide sprad of organic pollution of natural water on broad area. Coagulation and separation processes, as one of the more representing methods for removal of humic matter from natural water are realized today by using different coagulants with partial success. The main problems are in the domain of treatment of soft and hold waters with humic matter which are very vide spread.

According to the international clasiiϊcation of the patents (ICP) object of inovation is indicated with basic classification symbols Cl. C 02F1/52.

b) Technical problem

The gratest problem of purification of natural waters to drinking water standards is separation of humic matter, because they, amoung others, in the desinfection with chlorine give numerous halogenorganic maters with cancerogenous and mutagenous properties. For solving of this problem many methods use today, amoung others till now used dominant conventional technology of coagulation. All these technique have partial success, and there are intensive efforts for dissolving of this problem. Problems in coagulation of soft water with humic matter are esspecialy pronounced. Even more pronounced problem is coagulation of this type of water in cold climate, which is a frequent case.

With this inovation important effect of the coagulation process and separation from row water of humic matter of diferent characteristics is obtained. With this inovation high improvement in coagulation in the case of purification of soft water with humic matter, even at exstremly low temperature can be achieved.

With this inovation, from some type of row water, effect of reduction of organic matter till drinking water standard (consumption KMnθ4 smaler then 8,0 mg/1), and for water with high organic content better purification results with smaller investment in the following phases of purification is obtained. Solution in inovation is : simple, fast, effective and economic solution for removal of humic matter from row water with minimum changes in ionic content, without organic floculant and without limitation of folowing phases purification of drinking water. c) State of technic

Purification of the natural water with humic matter, for drinking water, is realised today, with several technological solutions : conventional treatment including several processes (coagulation with different schemes of flock separation), removal of humic matter on the membrane (ultrafiltration, nanofiltration and revers osmoses), oxydation with biofiltration and sorption prosesses.

In phase of purification of row water with coagulation of suspended matter and partly coloidal and dissolved organic matter are removed. For coagulation different scheme of the treatment are used today, Al and Fe salts with auxiliary coagulants for treatment of different types of the water. As auxiliary coagulant activated Siθ2 and different organic polimer are used .

For improvement of coagulation processes new salts are sintetized, inorganic polymers giving in the water polinuclear complex hidroxo-aluminium ions with cationic properties. Type of anions in the molecul enable pollimerisation giving to it properties of floculation matter which is very important for water difficilt for floculation.

On the west market they are : PAC, WAC, Megaflok etc., and in our country Koaflok (Patent P-551/95).

Great number of patented sollutions give a spectre of Al complex salts. The best, today, is the one which contains maximum homologs with 13 Al atoms in polimer, obtained by electrochemical procedure (Japan patent 24354 and 24355).

Unfortinately, stil special problem is presented with water containing humic matter, especialy soft water and coagulation in the low temperature conditions. Application of classical schemes of water treatment need enormous quantity of Al or Fe salts with low efects of purification. On the low temperatures purification of water with low ionic content with inorganic Al pollimers canot give floe, that is thet reason the existing technological schemes, having the best filters canot remove humic mater from water, as is confirmed by new data presented on the International Conference about "Removal of Humic Substances from Water" held in Norway 1999.

In the case of insufficient efficiency of removal of humic matter from water in addition several phases of the treatment are used: oxidation with ozone, sorption on the GAC, by that whole proccess is complicated and cost for treatment including capital cost and exploatation cost increase significantly.

Humic matter produce numerous problems in water supply (thay give colour, products of oxidation are degraded in water supply system serving as food for microbiological processes, with hlorine gives many halogenorganic substances, amoung them according to new data, chlorohydroxyfuranones are extremely important mutagens), and their removal from water is one of the priority tasks. In our country bacase of complexity and high treatment costs water containing humic matter is purified only partly, or purification don't exist. With demands for limitation of content purgable of halogenorganic matter in drinking water, removal of humic matter from row water is placed as priority.

In the numerous water supply systems in our country : system for water supply on the

Kopaonik, water reservoirs like Divcibare and others reduction of organic matter (consumption of

KMnθ4) isn't in drinking water standard range, ground water with veiy high organic content like

Kikinda, Zrenjanin and other are used without treatment except chlorination.

d) Presentation of the essence of inovation

Inovation given by this method is in great improvement of efficiency of humic matter coagulation obtained with mutual effects of two polymers, Al complex salts and activated Siθ2 in favorable pH range.

The essence is in the effect of neutralization of electricity on the moleculs of humic substances with this two pollymers and entrance of humic macromolekul in stable floe and it's effective removal from water.

Changable content of humic matter in the natural waters of different origin, as well as changes on the water sources with time, as is the case some surface water recuire changes in the fazes of coagulation. This is obtained by the chages of content of these two polymers. This relation, expressed as AI2O3 : Siθ2, according to experimental results for different types of water is betwen ό : 1 to 3 : 1.

Adaptation of relative ratio of two inorganic polymers as well as their real quantity to the type of humic matter in water is a part of the patented technology, inovation. Only good estimation of quantity and ratio of these two polimers for treated water give possibility for generation of stable floe and effective purification of drinking water, it is established as condition for application of this method.

Natural water with humic mater frequently have unpleasant ionic content, frequently due to shortage Ca and Mg. Adaptation of pH for optimisation of the coagulation and removal of humic matter frequently need of later neutralization with Ca(OH)2 and CO2, according to this conditions for improuvment of mineralization of drinking water are obtained.

Additional problem of loading of the scheme of the removal of humic matter by coagulation is high content of rezidual Al in the drinking water, and which is successfuly eliminated using this method, whose corect application is garant for obtaining of the most strict standards.

Inovation is tested in laboratory conditions, jar test, while only phase Al polimer application condition is tested in sity, that is giving data for conclusion about improvement effects of purification obtained by laboratory jar test. In the application this method does not have special demands compared to conventional coagulation process. As for conventional system, in jar test, phases of the coagulation and sedimentation are in domain : rapid mixing with 200 r/min. (2 min.), slow mixing with 15 - 30 r/min (10 min.) and precipitation cca. 20 min. by which this phase of purification is s finished.

Process on the instalation is deffined by conditions of the instalation. Adjustment of optimum pH, for the greatest number of water is in the range 5.5 to 6.5 (if it is necesary), realized before coagulants dosage with some of mineral acids (H2SO4, HC1 or with cationic resin H+ type), in that way with minimum changes on the ionic content, or that is all time in range of the drinking water quality standards, like this realized with Al2(Sθ4)3l8H2θ. For the natural water with low pH, type of water source on Kopaonik, adjustage of pH isn't nessesary, (excluding possible changes of water quality during a year when situation expect this), and finaly neutralization will be realized with Ca(OH)2 before filtration.

Dozage of the coagulant, Al polimer and activated Siθ2 is realized just before rapid mixing, and later adjustment of pH (if it is necessary) is realized after sedimentation.

Inorganic polymer is dosed without disolution, or in the range of disolution allowed by the producer, when worked with concentrated substances.

Activation of amorphous Siθ2 is realized by neutralization of alkalinity, 1,0 % solution, which imediately is diluted to 0.1 - 0.05 % solution with slow, mixing providing activity of Siθ2 for many hours use.

The doses of Al polimer and activated Siθ2 are deffined for a concrete case of purification and can vary in broad range, for Al polimer 2.0 - 25 mg/1 AI2O3 and activated Siθ2 from 0.5 - more than 5.0 mg/1.

e) Short ilustration of figure of the plan Investigations in laboratory conditions were realized with standard methodology, by jar test with propeler mixer changable speed from 10 - 200 r/min., which provided realization of experiments in defined conditions : rapid and slow mixing.

For investigation different comercial polimer : PAC, Megafloc and Koaflok were used. Mostly experiment were realized with Koaflok. Process of purification of row water by coagulation with separation floe on the instalation has phases given in the scheme 1.: Adjustment of the pH (if it is necessery), dosing of the koagulants (Al polimer and activated Siθ2) with mixing phases (rapid and slow mixing) and finally sedimentation and filtration. Adjustment of the pH before phase of coagulation (if it is necessary) is realized by dozing of mineral acids or by filtration of some part of the water flow (about 15 % and more persent, depanding on expected pH and type of water) trough column with H+ resin. Water for acidification is taken from basic flow, row water, or after sedimentation of filtration phases protecting H+ rasin polution. Neutralization of treated water is realized before filtration phases.

The method permits other purification schems. This is related to existing instalations, for example these with coagulation/direct filtration. In this case effects of the process is dependant on concentration of humic matter, or coagulant doses, because the filter run is depandant on these parameters.

f) Detailed description of the inovation

To the row water, before adjustment of the pH to app 5.5 - 6.5 range (if row water isn't in this in the source), and reduction of biologic activity (in the case treatment of the surface water resources is realized, desinfection in first step if the biologic activity limit sedimentation process), inorganic polimer Al and Si02 is added, pass through phases of rapid and slow mixing and after that removed floe by sedimentation during about 30 min, according to the standard procedure of jar test. Under the plant conditions realization of the procedure is defined by characteristics of the instalation.

Adjustment of the pH (for the row waters with low mineralization adjustment is realized with some of mineral acids : H2SO4 or HC1, but for waters with high bufer capacity where exist possibility for degradation of ionic content and water quality this realized by use of H+ cationic resin) for optimal effects of purification is realized on the begining of the process. Posible later corections, adjustment to range defined by drinking water standards and improvement water stability is realized after sedimentation, but before phase of filtration.

Efficiency of the removal of humic matter is depandant on the conditions of the procedure and for optimal conditions : doses of complex Al salts and activated Siθ2, as well as optimal pH value are defined for each case separately. For the ground water resources these values are stable, but for surface water they must be adjusted according to changes of characteristics of the treated water. All process is controled by some parameters of the water quality that give data about effect of the purification : turbidity, consumption of KMnθ4, colour, uv-extincion, PTHM and residual Al concentration.

All results of jar tests are related to characteristics of decanted water. Only some results refered to filtred water will be pointed out. By using inorganic polymer Al and activated Siθ2 as auxiliaty coagulants, by controling pH in the optimal range iprouvement of coagulation process and integral effects of purification compared to conventional treatment are obtained :

- reduction of organic matters, especialy humic matter, from water (calculated as consumption of KMnθ4 from 70 to 90 %), - high percent of organic matter as uv-extintion is remuved, which is very important according to the fact that this matter is the main precursor of halogenorganic matters (effects this reduction are in special cases 90 %),

- process of coagulation and separation is intensified even with extremly low temperature (process coagulation and sedimentation of water on Kopaonik is realized indepandant of low temperature),

- it reduces content of the THM prekursors in the purified water, rarely lower to MLC in the drinking water (PTHM reduced about 90 %),

- it attained especially important effects in the reduction value of colour even more then 95

%, - it attained extremely low concentration of residual Al in drinking water (for corectly performed coagulation process concentration Al is lower then 0.050 mg/1, according to this the most strict standard for drinking water quality is provided,

- it reduces consumption of Al salts (consumption Al is reduced for 2 to more then 5 times, compared to conventional treatment with As sulphate even with very high effects of purification, as the case of water purification from accumulation on the Div]ibare, fig. 4.3.),

- it reduces effects to the environment from mud from drinking water facilities from 50 - 80 %.

All cited parameters present more effective enhanced coagulation then that postuled by US EPA (1998). Presented examples of laboratory investigation ilustrate this conclusions.

Example 1. Results of laboratory investigations purification effects of ground water in Kikinda Row water has following characteristics : pH = 8 - 8.2, turbidity = 0.60 NTU, consumption of KMnθ4 = 28-30 mg/1, uv-ext. = 0.300 1/cm, PTHM = 350 μg/1, and CHCI3 = 300 μg/1.

By coagulation and sedimentation according to jar test methodology with optimum doses : koaflok (15 mg AI2O3/I), Siθ2 (2 mgSiθ2/l) i with pH near 7.0 water of characteristics was obtained : turbidity = 0.40 NTU, consumption of KMnθ4 = 9.4 mg/1, uv-ext. = 0.076 1/cm. Better effects of reduction of organic matter, consumption of KMnθ4 = 8.6 mg/1, is obtained with dosse of 10 mg AI2O3 at pH = 6.0. Lowering pH is limited by increasing of ionic strenght and sulphate or chloride content. Equivalent effects are obtained by ussing H+ cationic resin with simultaneous reduction of treated water hardness. This method need somewhat higher more investment, but it provides hardnes of the treated water in the range of drinking water quality standard.

On the fig. 1.1., and 1.2., some results of depandance of degree of the reduction of organic matter (consumption KMnθ4) and uv-extincion (as parameters water quality) in function of doses koaflok are given. In full-scale conditions, with effects of filtration, expected improvement of water quality and reduction of koaflok doses of about 20 %.

Example 2. Results of laboratory investigation purification effects of ground water of Zrenjanin

Row water has folloving characteristic : pH = 7.7 - 8.2, turbidity = 1.5 - 2.8 NTU, consumption of KMnθ4 = 52 mg/1, uv-ext. = 0.300 1/cm, colour = 50 - 60.

By coagulation and sedimentation according to jar test methodology with optimum doses : koaflok (20 mg AI2O3/I), Siθ2 (4 mgSiθ2/l) i with pH near 7.0 water following characteristics was obtained : turbidity = 0.65 NTU, consumption KMnθ4 = 16.1 mg/1, uv-ext. = 0.144 1/cm, colour = 5 mg Pt/1.

Better effects of organic matter reduction were obtained by lowering pH by using H+ cationic resin which limited increased hardness of water. This was obtained by passing some part, about 15 % or more persent tlirough H+ cationic resin with simultaneous reduction of treated water hardness. This method need more investment, but it provide of treated water hardnes in the range of drinking water quality standards.

On the fig. 2.1., and 2.2., some results of depandance degree of the organic matter reduction are given (consumption KM11O4) and uv-extincion (as parameters of water quality) in function of koaflok doses .

Example 3. Results of laboratory investigation of purification effects of surface water on Kopaonik. Row water has changable characteristics : pH = 5.2 - 7.5, turbidity about 0.6 NTU, consumption KMnθ4 = 8.6 - 12.7 mg/1, uv-ext. = 0.09 - 0.115 1/cm, colour = 15, PTHM = 150 - 230 μg/1, and CHCI3 = 120 μg/1.

Characteristics of this water are in the low ionic content and low temperature (parameter limiting coagulation possibility) and with high specific yield THM, as defined needed degre of humic mater reduction in the case of desinfection with chlorine.

By coagulation and sedimentation according to jar test methodology with optimum doses : koaflok (3 mg AI2O3/I), Siθ2 (0.5 - 1.0 mg Siθ2/l) i with pH near 7.0 water following characteristics was obtained : turbidity = 0.25 NTU, consumption KMnθ4 = 4.04 mg/1, uv-ext. = 0.005 1/cm, colour = 0.5 mg Pt/1, PTHM = 65 μg/1, and CHCI3 = 30 μg/1. On the fig. 3.1., and 3.2., some results of depandance degree of the organic matter reduction are given (consumption KM11O4) and uv-extincion (as parameters of water quality) in function of koaflok doses.

Example 4. Results of laboratori investigation of surface water effects purification from accumulation Divcibare

Row water has characteristics : pH = 7.1., turbidity about 3.0 NTU, consumption KMnθ4

= 26 mg/1, uv-ext. = 0.210 1/cm, colour = 20, PTHM = 650 μg/1, and CHCI3 = 500 μg/1.

Characteristics of this water is in the low ionic content and low temperature (parameter limiting coagulation possibility) and with high specific yield THM, which defined needed degre of humic mater reduction in the case of desinfection with chlorine.

By coagulation and sedimentation according to jar test methodology with optimum doses : koaflok (3.5 mg AI2O3/I), Siθ2 (1.0 mg Siθ2/T) i with pH near 7.0 water of following characteristics was abtained : turbidity = 0.18 NTU, consumption KMnθ4 ⁼ 4.0 mg/1, uv-ext. =

0.005 1/cm, colour = 1.5 mg Pt/1, PTHM = 65 μg/1, and CHCI3 = 30 μg/1.

Example 4.1. In other condition surface water from hipolimnion of this accumulation Divcibare had diferent characteristics, higher consumption of KMnθ4, higher uv-extincion and higher demand for coagulants.

Row water has had the following characteristic : pH = 7.3., turbidity about 3.8 NTU, consumption KMnθ4 = 32 mg/1, uv-ext. = 0.268 1/cm, colour = 33 mgPt/1, PTHM = μg/1, and

CHCI3 about μg/1.

After adjustment of pH to 6.0 coagulant is dozed : koaflok (9:0 mg AI2O3/I), Siθ2 (3.0 mg

Siθ2/l). After sedimentation new adjustment of pH and rapid flirtation (9 m/h) through sand and gravel (column 0.6 m high and with sand and gravel 0.6 - 4 mm) is performed water quality with : pH = 7.08, consumption KMnθ4 = 7.2 mg/1, turbidity = 0.15 NTU uv-ext. = 0.041 1/cm, colour = 2 mg Pt/1, residual Al = 0.030 mg/1 is obtained.

On the fig. 4.1., and 4.2., some results of depandance degree of the organic matter reduction (consumption KMnθ4) and uv-extincion (as parameters water quality) in function of doses koaflok are given.

On the tab. 4.3. effectivity of reduction of dissolved organic matter (consumption KMnθ4) for different schems of row water purification from lake Divcibare (lwith Al sulphate, 2-with Koaflok, and 3-with Koaflok with auxiliary coagulant), obtained on the jar test is presented.

Claims (3)

PATENT CLAIMS

1. Method for purification of natural water with humic matter to drinking water is, pointed by this, that removal of humic matter from row water under all temperature conditions, in the acid range is ensured by type of the water or by adding mineral acid or by ussing ionic H+ resin, after that treated with inorganic polymer Al and activated Siθ2 in optimal concentrations, defined in application and depandant on type of water vary in wide range (for Al polymer from 1.5 to over 20 mg/1 as AI2O3, and Siθ2 from 0.5 to over 5.0 mg/1) that under selected conditions of coagulation and separation of floe (by sedimentation, flotation or direct filtration) with adjustment of pH decanted water to the desirable range (by dose lime with or without CO2, with or without adjustment of hardness) and with following filtration maximal reduction of the humic matter with minimal consumption of chemicals and minimum concentration of the residual Al in drinking water will be ensured.

2. Method according to demand 1 is pointed by this, that is : a) in the case of soft water purification finaly neutralization realized with Ca(OH)2 and CO2 to desired pH and hardnes of the water, b) in the of case of hard water purification regulation acidity is obtained by passing one part of the flux through the column with H+ type of resin, by this removal of significant quantity of cation is obtained and than by final neutralization the best ionic content.

3. Using inorganic Al polymer and activated Siθ2 as coagulants for water with humic matter purification is apointed by this that in phase of application the most favorable contents and mutual relation this two chemicals are defined for obtaining the best effects of the purification depandant of type on water or composition of humic matter which is treated.