NEW BIODEGRADABLE ANTISCALANT PRODUCT FOR THE TREATMENT AND REUSE OF WASTEWATER WITH MEMBRANE SYSTEMS

Aumatell, Jordia; Bertran, Eudalda; Vidal, Danielaa; Marian, Irenea; Adroer, Núriaa*

aADIQUÍMICAC. Albert Llanas 32, 08024 - Barcelona (Spain)*nadroer@adiquimica.com

ABSTRACT

The growing need for water and the current shortage of resources means taking measures to promote water reuse. An alternative resource is regenerated water. When considering the use of this resource, it is necessary further improvement of the quality of treated water for reuse. In this framework, the use of membrane bioreactors (MBR) coupled to a reverse osmosis (RO) is becoming an increasingly attractive option for the treatment and reclamation of wastewater.

In the present study we developed the antiscalant product ADIC R0-44 (ADICGREEN RANGE) which is effective in protecting the mem-branes of reverse osmosis systems used for the purified waste water treatment. This new antiscalant product is especially effective for controlling precipitation of calcium phosphate and calcium carbonate, without acid dosing to prevent precipitation of calcium phosphate. Standard Operating data of the pilot plant wound reverse osmosis membrane, and the results of the autopsies of different elements con-firmed the efficacy of antiscalant developed.

The antiscalant ADIC R0-44 (ADICGREEN RANGE) is environmentally friendly because it does not contain phosphorus or nitrogen in their composition. New antiscalant immediate biodegradability studies were performed and the results indicated that it can be classified as biodegradable.

Specific software was developed to calculate the optimum dosage of antiscalant according to feed water composition, temperature and conversion of reverse osmosis, optimizing performance and minimizing plant operating costs.

2

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We also have to prevent inorganic scale

formation on the membrane surface. It is

therefore necessary that the water supply

is subjected to a suitable pretreatment.

The treated wastewater feeding a reverse

osmosis system usually have all the sub-

stances that cause membrane fouling:

organic matter, microbial load, colloidal

material, inorganic substances (phos-

phorus, nitrogen, calcium, carbonates,

etc..), and metals (iron, aluminum, etc..).

To improve the reverse osmosis process,

several methods are used to minimize the

fouling potential of the effluent fed to the

membranes. The problems of organic mat-

ter and colloidal matter, in most cases are

minimized using ultrafiltration (UF) and mi-

crofiltration (MF) as a pretreatment. Moreo-

ver, membranes have been developed or

improved to adapt to secondary effluents

characteristics. It is promoted the use

of specific membranes resistant to foul-

ing caused by organic material, colloidal

and microorganisms by a modification of

membrane surface properties: the zeta

potential, roughness, etc. (Bates, 1998;

Redondo & Lomax, 2001). To control mi-

crobiological load, chlorine can be dosed

before pretreatment to prevent biological

growth at this stage, and chlorine can be

dosed later on to minimize colonization of

the membranes. Reverse osmosis poly-

amide membranes have little tolerance to

chlorine, thus it is essential to neutralize

the excess chlorine in feed water before

membrane racks. Another option is to use

non-oxidizing biocides which do not dam-

age the membranes.

Because of the salinity concentration pro-

cess that takes place inside the reverse

osmosis membranes, exists a possibility of

corporation of water regenerating stations of

such plants. To this aim, existing technolo-

gies have been incorporated and applied,

and also specific technologies have been

developed with the aim to obtain different

qualities of water suitable for reuse. In this

framework, the use of membrane bioreac-

tors (MBR) coupled to a reverse osmosis

(RO) is becoming an increasingly attractive

option for the treatment and reclamation of

wastewater, due to the high efficiency of

the process and high quality effluent, when

combining the two technologies. (Reith &

Birkenhead, 1998; Marti et al. 2011).

Reverse osmosis membrane Systems are

becoming more frequently used in the re-

generation of the treated wastewater to

meet the growing demand for high quality

water (Latvian et al., 2005) for industrial use

(boiler feed, water process, etc.), for envi-

ronmental uses (groundwater recharge,

hydraulic barrier against seawater intrusion,

etc.), for agricultural purposes (irrigation)

and recreational (golf course irrigation).

The use of reverse osmosis as tertiary

treatment plants regeneration has limita-

tions associated with the quality of the efflu-

ent to be treated. The effectiveness of the

reverse osmosis is limited by membrane

fouling. The deposition of substances on

the surface of the membrane prevents wa-

ter transport through the membrane and

decreases the quality of the permeated

water. Rapid fouling requires membrane

cleaning more frequently, reducing the

useful life of the membrane and increases

operating costs. Pretreatment of reverse

osmosis plants is designed to produce a

water supply to the membranes with low

fouling potential: free of suspended sol-

ids, colloidal matter and microorganisms.

INTRODUCTION

The growing need for water and the cur-

rent shortage of resources means taking

measures to promote reuse and thus

achieve sustainable management of wa-

ter resources. Mediterranean regions are

among the most vulnerable to this short-

age, and that is why there have been nu-

merous studies in the field of wastewater

treatment, the processes of regeneration

and subsequent reuse.

An alternative resource is regenerated wa-

ter, treated wastewater that has undergone

an additional or complementary process

that permits proper quality that is intended

to use (RD 1620/2007). When consider-

ing the use of this resource, it is necessary

further improvement of the quality of treated

water for reuse, making it essential to apply

advanced tertiary processes. The selection

of processes or technologies needed for

the regeneration of the treated wastewater

involves prior knowledge of the type of ef-

fluent to be treated, its quality over time and

the quality required in the reclaimed water.

The processes used for regeneration are

oriented mainly in the reduction of suspend-

ed matter and colloidal and disinfection.

Depending on the final use of the reclaimed

water, it can also be considered removing

soluble salts, dissolved solids, organic and

inorganic compounds. Although initially ef-

fluents from wastewater treatment plants

(WWTP) have been treated to meet the

requirements of the rules of existing dis-

charges, since the publication of Royal De-

cree 1620/2007 of December 7 in Spain,

concerning to the required regenerated

water quality characteristics depending on

the intended use. Thereof, it involves the in-

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3

limiting the conversion of reverse osmosis

to prevent exceeding solubility limits, the

strategies used to prevent scale formation

are controlling pH by dosing acid to reduce

the fouling potential, or using an anti -foul-

ing. Antiscalants are dosed in the reverse

osmosis feed at low concentrations to pre-

vent fouling rejection.

A study was conducted with ADICRO scien-

tific software to simulate the behavior of treat-

ed wastewater in reverse osmosis, based

on the feed water temperature, the plant

conversion and membranes used (Adroer et

al. 2001). The software calculates ADICRO

osmotic pressure, ionic strength and values

corrected for the ionic strength of the solu-

bility products of the susceptible species to

precipitate. These values are used to calcu-

late the saturation index (ISS), the Langelier

index, Stiff & Davis index, rates of fouling and

fouling potentials to predict whether a risk

of fouling on the membrane. ADICRO soft-

ware also recommends the most suitable

antiscalant and calculates the optimal dose

of inhibitor to protect the membranes against

the formation and deposition of insoluble

species. The program indicates whether the

treated water will be within allowable limits for

different saturation indices. The software also

calculates the dose necessary acid or base

to lower or raise the pH of the feed water to

obtain the desired value.

From analysis of the feed water of Table 1,

and operating at a conversion of 70% and

a temperature of 18 ° C, a study was made

of fouling potential of different species sus-

ceptible to precipitate in the rejection of re-

verse osmosis with ADICRO software.

Table 2 shows the embedding poten-

tial of rejection water without antiscal-

determining parameter in the environmental

behavior of chemicals and a desirable prop-

erty of the products that are released in large

quantities into the wild, such as detergents,

pesticides, water treatment, etc.. (Vázquez-

Rodríguez & Icela Beltran-Hernandez, 2004).

Through the process known as biodegrada-

tion, microorganisms transformed organic

compounds, most of the times, in com-

pounds less toxic than the originals ones.

The biodegradability has been defined as

the intrinsic ability of a substance to be trans-

formed into a simpler chemical structure by

microbes (Ottenbrite & Albertsson, 1992).

The aim of this study is to evaluate the effec-

tiveness of the new antiscalant ADIC R0-44

(ADICGREEN RANGE), which is biodegrad-

able and environmentally friendly, in reverse

osmosis systems fed by treated wastewater.

STUDY OF THE FOULING CAPAC-ITY OF REJECTED REVERSE OS-MOSIS WATER FED BY TREATED WASTEWATER

A study of the fouling capacity of reject-

ed reverse osmosis water fed by treated

wastewater from a membrane bioreactor

(MBR) was performed. Table 1 shows the

composition of the feed water to the re-

verse osmosis plant and reject water, op-

erating at a conversion of 70%. Solubility

limits of the compounds can be exceeded

in rejection where they can precipitate in

the membrane surface. The precipitation is

due to the high concentration of the com-

ponents of the insoluble salts in the con-

centrate. The most common fouling are

caused by calcium carbonate, calcium sul-

fate, calcium fluoride, calcium phosphate,

strontium sulfate, barium sulfate, iron, alu-

minum, manganese and silica. Besides

exceeding the limit of solubility of insoluble

inorganic compounds (calcium carbonate,

calcium sulfate, calcium phosphate, etc.).

After the removal of suspended solids and

colloidal organic matter and by UF / MF or

secondary effluent from the conventional

wastewater treatment, membranes must be

protected against the precipitation of insolu-

ble inorganic compounds. One of the most

serious problems affecting the performance

of the membranes in these applications is

the high concentration of phosphate. The

most common fouling, for example calcium

carbonate, calcium sulfate, and iron oxides

can be prevented and controlled by a variety

of existing precipitation inhibitors. However,

these conventional antiscalants are not ef-

fective to control calcium phosphate scale in

such facilities. The most widespread method

for inhibiting calcium phosphate precipitation

in reverse osmosis systems is the reduction

of water pH with acid. The dosage of acid

means an increase in operating costs due to

the large quantities of acid required and the

occurrence of corrosion problems.

The antiscalant used in reverse osmo-

sis systems in their formulation containing

phosphorus are effective as scale inhibitors

and compatible with reverse osmosis mem-

branes, however when these antiscalants

are discharged into the environment, they

behave as nutrients for algae and bacteria,

which may lead to eutrophication. Antiscal-

ant products without or with very low levels

of phosphorus and nitrogen in its formula-

tion, minimize the risk of eutrophication.

As an added value to the inherent proper-

ties of these products, their permanence in

the environment must take into account and

therefore must also determine their capac-

ity to biodegradation. Biodegradability is a

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SCALING IN REVERSE OSMO-SIS SYSTEMS USED IN TREATED WASTEWATER REGENERATION PROCESSES

Development of an antiscalant biodegrad-

able and environmentally friendly to inhibit

the precipitation of calcium phosphate and

calcium carbonate

Calcium carbonate and calcium phosphate

are insoluble problematic compounds in

rejection water in reverse osmosis. To de-

sign and develop the antiscalant the fol-

lowing aspects are defined:

1. Antiscalant operating limits. The product

should be effective to prevent precipitation

of insoluble calcium phosphate and calcium

carbonate on the membrane surface. Fur-

thermore, the inhibitor should have antiscal-

ant properties against the most common

deposits (e.g. calcium sulfate, calcium fluo-

ride, iron, silica, etc.). It should demonstrate

the efficacy of the final formulation against all

types of species susceptible to precipitate.

The effectiveness of the inhibitor should be

tested first in laboratory-scale plant, before

applying it into actual floor.

2. Formulation. The antiscalant will be

dosed in reverse osmosis polyamide mem-

brane systems and nanofiltration used for

wastewater regeneration. This requirement

will determine the design of the product,

i.e., may be neither an oxidant nor cationic

product, and shall also be biodegradable

and environmentally friendly, i.e. must not

contain either phosphorus or nitrogen in

their composition.

3. Dosage. A methodology was developed to

reverse osmosis pilot plant laboratory scale to

model designed inhibitor dosage. Antiscalant

maximum permissible for the different

supersaturation rates and fouling rates.

Embedding a potential higher than 100%

means that the corresponding saturation

index is greater than the maximum allow-

able limit for this ratio and the insoluble

compound can precipitate. Data refer to

the dosing system without antiscalant.

The simulation results show that the foul-

ing potential for calcium carbonate and

calcium phosphate exceed the value of

100%, indicating that there is a risk of

fouling of the membrane by these two

compounds. For other insoluble species

embedding potentials are within allow-

able limits.

EXPERIMENTAL STUDY OF THE EFFECTIVENESS OF ADIC R0-44 (ADICGREEN RANGE) AVOIDING

ant treatment. The scaling potential is

expressed as the percentage of the

Parameter Feed WaterSimulated rejected water at 70% conversion (software ADICRO)

pH 7.55 7.97

Calcium 98 mg/L Ca 327 mg/L Ca

Magnesium 40 mg/L Mg 133 mg/L Mg

Sodium 252 mg/L Na 840 mg/L Na

Potasium 20 mg/L K 67 mg/L K

Iron 0.017 mg/L Fe 0.057 mg/L Fe

Barium <0.001 mg/L Ba <0.001 mg/L Ba

Aluminium 0.108 mg/L Al 0.360 mg/L Al

Manganium 0.049 mg/L Mn 0.163 mg/L Mn

Sulfate 166 mg/L SO4 553 mg/L SO4

Chloride 441 mg/L Cl 1470 mg/L Cl

Bicarbonate 217.2 mg/L HCO3 639.9 mg/L HCO3

Carbonate 1.09 mg/L CO3 13.5 mg/L CO3

CO2 Free 12.9 mg/L H2CO3 12.9 mg/L H2CO3

Silica 15.0 mg/L SiO2 50.0 mg/L SiO2

Fosfate 3.83 mg/L PO4 12.77 mg/L PO4

Ionic Strenght (IS) 0.024 0.074

Table 1. Feed water analysis and simulation of rejected water at 70% conversion and a temperature of 18ºC.

Insoluble Compound

Fouling potential for the synthetic water used in the study (maximum allowable limit %)

CaCO3 153.8%

CaSO4 8.7%

CaF2 0.0%

Ca3(PO4)2 366885.9%

SrSO4 0.0%

BaSO4 0.0%

Iron 54.9%

Aluminium 29.9%

Manganesium 51.5%

Silica 38.3%

Table 2. Embedding potential for rejection insoluble compounds (70% conversion) without antiscalant treatment.

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5

water, simulating rejection for a 70% con-

version. ADICRO software predictions for

synthetic water indicate that the solubilities

of calcium carbonate (CaCO3) and calci-

um phosphate (Ca3 (PO4) 2) exceeds the

maximum allowable limit (> 100%).

The results obtained in testing the efficacy

of different formulations made in a flat flow

membrane cell reverse osmosis labora-

tory scale, making it possible to isolate

the most effective formulation to inhibit

scale formation. The antiscalant ADIC R0-

44 (ADICGREEN RANGE) was the most

effective formulation. The ADIC R0-44

(ADICGREEN RANGE) has the ability to

inhibit 100% precipitation of calcium phos-

phate and calcium carbonate. Moreover,

the evaluated antiscalant product, sepa-

rate anions and cations solutions were

added to obtain a water with a fouling

capacity equivalent to a 70% conversion.

Table 3 shows the composition of the

synthetic water used during trials.

Hydranautics CPA2-2540 membrane was

used. The feed pressure, as specified by

the manufacturer, was controlled at 15.5

bar. The pH was controlled at 7.97, cor-

responding to the pH obtained in the simu-

lation of rejected treated wastewater. The

temperature was maintain at 18 ° C. Differ-

ent concentrations of antiscalant product

were dosed evaluating the efficacy of each

concentration to inhibit the precipitation of

insoluble compounds.

To assess the efficacy of the antiscalant

and calculate the inhibition of scale for-

mation in each test operating parameters

were monitored: normalized permeate

flow, normalized salt rejection, feed pres-

sure, pressure difference between feed

and rejection (Delta P), pH and tempera-

ture. Chemical analysis of the feed and

permeate were also periodically complet-

ed. After the tests studies with scanning

electron microscopy with energy disper-

sive analysis by X-ray (SEM-EDX) of the

membrane surface were conducted to

know the chemical composition and mor-

phology of the deposited scale.

To calculate the inhibition of scale formation,

the results obtained in each test were refer-

enced to the evolution of analytical and op-

erational parameters in the same conditions

without antiscalant treatment (blank).

Figure 1 shows the fouling potential of

species susceptible of precipitation which

were contained in the untreated synthetic

feed water dose should be in a 1-5 ppm range.

4. Define approvals the final formulation of

the inhibitor must overcome: antiscalant

compatibility with different membranes,

environmental requirements for disposal.

During the antiscalant development pro-

cess the efficacy of several formulations

for inhibiting fouling in membrane systems

was evaluated. The following dynamic

tests were performed:

1. In a first phase, antiscalant efficacy tests

were performed on a flat flow membrane

reverse osmosis cell laboratory scale. These

trials allowed the isolation and identification of

the antiscalant that had the best performance.

2. To confirm the effectiveness of the se-

lected antiscalant in the first stage and

develop a dosage model, we used a re-

verse osmosis pilot plant which consists

on a pressure tube to a single membrane

wrapped Hydranautics CPA2-2540.

Both experiments, flat flow membrane re-

verse osmosis cell, and wound membrane

pilot plant were carried out operating with

the total rejection and permeate recircula-

tion to the feed tank in order to maintain

the water concentration constant. The res-

ervoir level was kept constant by adding

distilled water to minimize the potential loss

of water by evaporation. The pH and tem-

perature were controlled to maintain these

parameters at the desired set point.

In all assays, a synthetic water was used

to work under strictly controlled condi-

tions. At the same matrix, correspond-

ing to residual water (Table 1) treated by

a membrane bioreactor which contained

ParameterSynthetic water used in the assays

pH 7.97

Calcium 327 mg/L Ca

Magnesium 40 mg/L Mg

Sodium 1148 mg/L Na

Potasium 361 mg/L K

Iron 0.017 mg/L Fe

Barium <0.001 mg/L Ba

Aluminium 0.108 mg/L Al

Manganesium 0.049 mg/L Mn

Sulfate 553 mg/L SO4

Chlorine 1933 mg/L Cl

Bicarbonate 707.4 mg/L HCO3

Carbonate 13.0 mg/L CO3

Free CO2 14.1 mg/L H2CO3

Silica 15.0 mg/L SiO2

Fosfate 12.8 mg/L PO4

Ionic Strenght 0.087

Table 3. Synthetic water composition which simulates the rejection with a conversion of 70% used for flat flow membrane cell assays and reverse osmosis pilot plant of wound membrane Hydranautics CPA2-2540

6

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conductivity, conductivity rejection conduc-

tivity permeate, feed temperature and pH.

During operation of the plant wound re-

verse osmosis membrane system con-

ditions such as temperature, pressure

and feed water quality may vary, causing

variations in productivity and quality of the

permeated water. To evaluate the perfor-

mance of the system is necessary to com-

pare the evolution of the parameters in the

same conditions. Therefore it is necessary

to convert data obtained in operating cur-

rent conditions to a set of data selected in

standard conditions, thereby normalize the

behavior of the plant. The change in the

standard parameters indicates a possible

problem in the operation of the plant.

To evaluate the effectiveness of the ADIC

R0-44 (ADICGREEN RANGE) front foul-

ing was studied evolution permeate flow,

the salt rejection and the Delta P with-

out antiscalant treatment and dosage

of ADIC R0-44 (ADICGREEN RANGE).

These parameters are used as indica-

tors of membrane fouling. The evaluation

was conducted by normalizing analytically

operating data according to the standard

method ASTM D 4516 Standard Practice

for Standardizing Reverse Osmosis Perfor-

mance Data (ASTM, 2010).

Figures 2, 3 and 4 shows the normalized

permeate flow, the salt rejection and the

Delta P standard membrane in the tests

without antiscalant treatment and dosage

of the ADIC R0-44 (ADICGREEN RANGE).

The results of experimental tests without an-

tiscalant treatment showed that the normal-

ized permeate flow decreased few hours

about 30%. The salt rejection decreased

slightly throughout the test. The DeltaP pro-

in a mineral medium, at neutral pH and at

a temperature between 20 and 25°C. The

test substance is added to a defined con-

centration, as the sole carbon and energy

source. The inoculum consists of a natural

microbial population which has not been

exposed to the test compound. In this study

methods were used to evaluate the biodeg-

radability that has been standardized by the

(OECD). These are the most commonly

used tests of biodegradability internationally

and they derive most standardized methods

by different international organizations. The

results indicated that the ADIC GREEN 44

may be classified as biodegradable.

EVALUATION OF THE EFFEC-TIVENESS OF THE ANTISCAL-ANT ADIC R0-44 (ADICGREEN RANGE) IN PILOT PLANT OF RE-VERSE OSMOSIS MEMBRANE ROLLED.

Effective control system and data acquisi-

tion, installed in the pilot plant wound re-

verse osmosis membrane, was monitored

behavior of reverse osmosis membranes

during rehearsals without antiscalant treat-

ment and dosage ADIC R0-44 (ADIC-

GREEN RANGE). The pilot plant is highly

orchestrated and monitor the following

parameters: Feed pressure, the permeate

pressure, rejection pressure, Delta P, feed

rate, rate of rejection, permeate flow, feed

this formulation is environmentally friendly

because it does not contain phosphorus

or nitrogen in their composition.

The ADIC R0-44 (ADICGREEN RANGE)

is specific for inhibiting the precipitation of

insoluble compounds of phosphorus and

calcium carbonate in the membranes of the

reverse osmosis process used in regenera-

tion of purified waste water. The inhibitor is

a synergistic blend of antiscalant developed

to protect the membranes against calcium

phosphate scale formation without the need

of addition of acid for pH control. And also, it

is highly effective to inhibit scale formation of

insoluble compounds most commonly used:

calcium carbonate, calcium fluoride, calcium

sulfate, strontium sulfate, barium sulfate, iron,

aluminum, manganese and silica.

IMMEDIATE TESTS OF BIODEG-RADABILITY OF THE ANTISCA-LANT ADIC R0-44 (ADICGREEN RANGE)

The Organisation for Economic Coopera-

tion and Development (OECD) has stand-

ardized several ready biodegradability tests.

To study the biodegradability of ADIC R0-44

(ADICGREEN RANGE) was used biodegra-

dability test method OECD 301A (ready bi-

odegradability) (OECD, 1992). The general

principle of these tests is the static aerobic

incubation of a reduced amount of biomass

Figure 1. Scale potential for synthetic water insoluble compounds without antiscalant treatment.

technical article

7

gressively increased approximately 25%.

The evolution of the three parameters oc-

curred indicating that membrane fouling.

The results of the test when dosed ADIC

R0-44 (ADICGREEN RANGE) indicated that

the permeate flow, the standard salt rejec-

tion and Delta P were stable, unchanged

during the test period lasted. The evolution

of the standard parameters indicates that

the antiscalant is effective to prevent fouling

of reverse osmosis membranes.

To validate the effectiveness of the antiscal-

ant, autopsies were performed studies

membranes and scanning electron micros-

copy with energy dispersive analysis by

X-ray (SEM-EDX) of the elements after the

test without antiscalant treatment and at the

end testing after dosing ADIC R0-44 (ADIC-

GREEN RANGE).

SEM-EDX analysis allowed us to study the

atomic composition of the reservoir mem-

brane surface. For the observation and EDX

microanalysis, we used a scanning electron

microscope S Stereoscan-360 (Cambridge

Instruments) with tungsten thermionic gun

coupled to a separation system microanaly-

sis X-ray INCA Energy Series 200 (Oxford

Instruments) with des detection of beryllium.

The scanning electron microscope (SEM)

allows high resolution imaging of chemi-

cal and topographical characteristics of the

reservoir surface and particles under study.

The micrographs corresponding to images

of “Contrast-Z” provide additional information

on the composition of the deposit. This tech-

nique enhances the chemical sensitivity of

the image. The image of “Contrast-Z” is pro-

portional to the atomic number of the chemi-

cal elements. Different compositions relate

to a gray scale: elements with higher atomic Figure 4. Evolution of the Delta P without antiscalant and with ADIC R0-44 (ADICGREEN RANGE) dosage.

Figure 3. Evolution of the salt rejection without antiscalant and with ADIC R0-44 (ADICGREEN RANGE) dosage.

Figure 2. Evolution of the normalized flow without antiscalant treatment and dosage of ADIC R0-44 (ADICGREEN RANGE).

8

technical article

layer of the membrane as a function of

coating thickness.

Figure 5 (a) shows an image of “Contrast-Z”

at low magnification obtained by SEM of the

surface of the membrane after the test with-

out antiscalant treatment. It was noted that

the membrane surface was contaminated by

deposit a layer of uniformly distributed. Figure

5 (b) corresponds to an increase in “Con-

trast-Z ‘of the deposit covered the surface of

the membrane. Figure 5 (c) corresponds to

the spectrum of EDX analysis of the deposit.

EDX analysis results showed that the deposit

consisted primarily of calcium phosphate

and calcium carbonate. The presence of

phosphorus is because the feed water com-

ing from the reverse osmosis which was a

BRM domestic wastewater. The presence of

phosphate and calcium in the feed water of

a reverse osmosis results in the precipitation

of calcium phosphate in the rejection (Jacob,

2001). Phosphate is multivalent and can oc-

cur in a variety of forms with different solubili-

ties. The crystallization is very difficult, and is

the most common form amorphous deposit

on the surface of the membrane.

total elements obtained in this analysis. The

peak intensity increases as the relative abun-

dance of the element on the total of elements

in the sample obtained. The samples were

dried by critical point process, mounted in

the holder of the microscope and coated

with a thin layer of graphite to improve con-

ductivity. Membrane samples were coated

with graphite to make them conductive, for

this reason the carbon spectra was not taken

into account in the study of the composition.

The active part of the polyamide mem-

branes are composed of three layers.

There is a microporous polysulfone layer,

supported by a polyester nonwoven web.

On top of the polysulfone microporous lay-

er is a very thin dense layer of polyamide.

In an EDX spectrum of the surface of the

membrane is detected presence of sulfur.

Sulfur detection comes from sulfur which is

part of the microporous polysulfone layer.

The peak intensity sulfur EDX spectra indi-

cate the thickness of the deposit adhering

to the membrane. The electron beam in-

cident on the sample at the EDX analysis,

more or less easily reach the polysulfone

number correspond to the lighter areas of

the photomicrograph, while dark or black ar-

eas correspond to elements with low atomic

number (indicating the presence of organic

matter). Analysis by energy dispersive X-ray

(EDX) allows to know the chemical elements

in the different parts of a sample, and also

allows you to see the distribution of these

elements in the sample. The results are pre-

sented in a composition of energy spectrum:

peak intensity of energy based on keV. The

peak intensity of each element is indicative

of the relative amount of the element on the

Figure 5. SEM-EDX analysis of the surface of the membrane without antiscalant treatment (a) micrograph of “Contrast-Z” (magnification 200x) obtained by SEM. (b) Photomicrograph of “Contrast-Z” enlarged (magnification 1000x) obtained by SEM. (c) depositing EDX spectra of the membrane surface.

Figure 6. SEM-EDX analysis of the surface of the membrane dosing ADIC R0-44 (ADICGREEN RANGE) (a) Number micrograph (magnification 200x) obtained by SEM. (b) EDX spectra of the membrane surface. (c) Number obtained by SEM micrograph of the particle enlarged (magnification 2104x). (c) the particle EDX spectra corresponding to organic

technical article

9

water fouling of reverse osmosis, and en-

sure that the system is perfectly protected

against fouling for all species susceptible

to precipitate. The experimental results

also allowed to model potential reduction

embedding insoluble species rejection

based on the concentration of antiscalant.

Theoretical study was performed with the

treated waste water from the MBR (Table

1) to determine the optimal conversion of

of the tests enabled the calculation of the

percentage inhibition for each compound in-

soluble precipitation depending on the con-

centration of antiscalant dosage.

From the results of the experimental de-

sign was constructed a model of dosage

antiscalant ADIC R0-44 (ADICGREEN

RANGE), which calculates the optimal

dose of power based inhibitor of reject

Figures 6 (a) and 6 (b) correspond to a low

magnification micrograph topographic and

EDX analysis of the surface of the test mem-

brane dosing ADIC R0-44 (ADICGREEN

RANGE). The results of SEM-EDX analysis

of the surface of the membrane indicated no

presence of inorganic scale. Only showed

the presence of isolated particles and im-

purities of organic origin. The sulfur detected

in the EDX spectrum (Figure 6 (b)) coming

from the sulfur which is part of the layer of

microporous polysulfone membrane. Figure

6 (c) corresponds to an enlargement of a

particle. EDX analysis indicated that the parti-

cle consisted of organic matter (Figure 6 (d)).

We conclude that the ADIC R0-44 (ADIC-

GREEN RANGE) is effective for control-

ling precipitation of calcium phosphate

and calcium carbonate in reverse osmo-

sis systems used for the purified waste

water treatment.

DEVELOPMENT OF A MODEL OF DOSAGE OF ADIC GREEN -44

A model was developed for dosing the ADIC

R0-44 (ADICGREEN RANGE). The model

estimates the optimal dose for antiscalant in-

hibiting scale formation in the reverse osmo-

sis rejection. The mathematical model was

developed from the results of tests in pilot

plant wound reverse osmosis membrane.

To design the experimental test suite to per-

form experimental design was applied where

they took into account the following varia-

bles: concentration of antiscalant and scaling

potential for each species susceptible to pre-

cipitate rejection. They conducted a series of

tests in the pilot plant wound membrane,

where they tested the ADIC R0-44 (ADIC-

GREEN RANGE) at different concentrations

and under different conditions for each spe-

cies insoluble supersaturation. The results

Figure 7. Scale potentials for each species insoluble rejection without antiscalant treatment and dosage of ADIC R0-44 (ADICGREEN RANGE) to a conversion of 70%.

Figure 8. Scale potentials for each species insoluble rejection without antiscalant treatment and dosage of ADIC R0-44 (ADICGREEN RANGE) to a conversion of 75%.

10

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- Developed the antiscalant ADIC R0-44

(ADICGREEN RANGE), which is an inhibi-

tor of scale formation, effective for protect-

ing the membranes of reverse osmosis

systems used for the purified waste water

treatment. The antiscalant is especially ef-

fective for controlling precipitation of calcium

phosphate and calcium carbonate, without

acid dosing to prevent precipitation of cal-

cium phosphate.

- The antiscalant ADIC R0-44 (ADIC-

GREEN RANGE) is environmentally friendly

because it does not contain phosphorus

or nitrogen in their composition. Biodegra-

dability studies were performed immediate

new antiscalant and the results indicated

that can be classified as biodegradable.

- The software ADICRO is a useful tool to

optimize antiscalant dosage based on the

composition of the feed water temperature

and the conversion of the reverse osmosis

plant, optimizing performance and minimiz-

ing plant operating costs.

ACKNOWLEGMENTS

This work has been partially funded by the

CDTI (Centre for Industrial Technological

Development) and the ERDF (European

Regional Development Fund) awarded the

project called “Natural products and low

environmental impact of seawater desali-

nation and brackish” (call of 2010).

BIBLIOGRAPHY

- Adroer, M., Bodas J., Coma J., 2001.

Treatment calculation program for reverse os-

mosis. Water Technology, 215, 58-74.

- American Society for Testing and Materials

(ASTM), Standard Practice for Standardizing

Reverse Osmosis Performance Data, ASTM

Designation D 4516-00, Annual Book of

ASTM Standards, Volum 11.02, 2010.

- Bates, W. T., 1998. Reducing the foul-

the reverse osmosis system and to oper-

ate without danger of scaling and no dosing

of acid to prevent precipitation of calcium

phosphate. Were raised in several stages

of the conversion function of the system.

From the models developed was calculated

optimal dose of ADIC R0-44 (ADICGREEN

RANGE) for each of the scenarios, and pre-

dicted reduction potentials inlay antiscalant

treatment recommended.

Figures 7 and 8 shows the simulated results

of reduction potentials of reject water fouling

of reverse osmosis to a conversion of 70%

and 75% respectively, when dosed ADIC rec-

ommended concentration GREEN-44. The

scaling potential for calcium carbonate and

calcium phosphate decrease to values lower

than 100% for each of the conversions. The

system is perfectly protected against scaling

until a conversion of 75% without acid dosing

to prevent precipitation of calcium phosphate.

The mathematical model of dosage antisca-

lant ADIC R0-44 (ADICGREEN RANGE), the

model reduction potentials and embedding

knowledge gained during the pilot phase

were incorporated into the software ADI-

CRO. The program predicts the potential

fouling and recommends the optimal dose

ADIC R0-44 (ADICGREEN RANGE) to ob-

tain complete protection against scaling

and fouling of reverse osmosis membranes

in the regeneration processes purified

waste water.

CONCLUSIONS

- A study was conducted on the power in-

crusted of the rejection of a reverse osmo-

sis system fed by water treated wastewater

from a membrane bioreactor. The results

indicate that there is a risk of embedding

the membranes by calcium phosphate and

calcium carbonate.