The Wadi Ma'in Zara and Mujib Water Treatment and Conveyance Project

The Wadi Ma'in Zara and Mujib Water Treatment
                                and Conveyance Project

                       P. Temple Ballard, Infilco Degremont Inc. USA
                        Véronique Bonnélye, Degremont S.A., France
                            Miguel Angel Sanz, Degremont Spain
                            Marc Pétry, Degrémont SA, France

Abstract

The in-depth testing to determine optimum pretreatment and the design philosophy to
optimize RO performance efficiency and minimize energy consumption are detailed for one
of the largest brackish water RO projects in the world.
The Wadi Ma’in, Zara, and Mujib Water Treatment and Conveyance Project was awarded to
a consortium of Infilco Degremont, Inc., The Morganti Group, Inc. and Metcalf & Eddy in the
fall of 2003 and started mid 2006. The plant is provide approximately 40% of the water
requirement for the people of Amman, Jordan. This was considered a very critical project by
the government of Jordan, as many of the homes in Amman only received water through their
taps one day per week. The plant is located near the Dead Sea and treated water is transmitted
by a 40-kilometer pipeline and multiple pump stations to Amman. The plant capacity is 47
million m3/year (128,767 m3/d), one of the larger brackish water RO plants in the world.
The brackish water sources for this plant include the Mujib River, the Wadi Ma’in Zarqa
River and the Zara hot spring. The TDS for the combined sources is approximately 1475
mg/l average and 1980 mg/l maximum. These three source waters present a significant
treatment challenge due to greatly varying temperature as well as high concentrations of silica
and barium, and high fouling indices. The system is required to meet strict water quality
standards (similar to WHO / USEPA) with minimum RO recovery of 85%.
Four seasonal laboratory pilot studies were completed to determine the optimum pretreatment.
In addition to the main treatment train which includes the clarification, filtration, and reverse
osmosis, the filter backwash water is also treated via a secondary train which includes
clarification and UV disinfection to ensure proper microbial removal / inactivation efficiency.
The RO design includes three stages and is designed for a recovery rate of 90% under average
design conditions and of 85% under worst-case combined conditions of raw water quality,
silica being the limiting parameter. Booster pumps are implemented in three-stage design to
minimize energy consumption. Reject from the RO system is disposed to the Dead Sea.
The Plant delivered the first potable water production to Amman in August 2006.

Introduction
The Wadi Ma’in, Zara, and Mujib Water Treatment and Conveyance Project was awarded to
a consortium of Infilco Degremont, Inc., The Morganti Group, Inc. and Metcalf & Eddy in the
fall of 2003 and is scheduled to be completed in 26 months (June 2006). The plant is
providing approximately 40% of the water requirement for the people of Amman, Jordan.
This was considered a very critical project by the government of Jordan, as many of the
homes in Amman only received water through their taps one day per week. The plant is
located near the Dead Sea and water will be transmitted by a 40-kilometer pipeline and
multiple pump stations to Amman. The plant capacity is 47 million m3/day (34 MGD), one of

the larger brackish water RO plants in the world. The brackish water sources (Figure 1) for
this plant included the Wadi Mujib River, the Wadi Ma’in Zarqa River and the Zara hot
spring. These three source waters varied substantially in key parameters – additionally, there
was substantial variance due to climatic fluctuation.
The combination of
    multiple surface water sources with high fouling tendency (SDI>20 extrapolated)
    significant presence of many difficult ions (silica, barium) and high scaling factor (LSI)
    the presence of organic matter
    high and varying temperatures (20 – 40 º C)
combined with the requirement for high RO recovery (>85%) presented a substantial
challenge for the pretreatment design.

Figure 1. Map of Jordan representing Amman to the Dead Sea: (the stars’s representing the
                            3 point sources of the raw water)

The treated water was required to meet the following standards:
   all Jordanian potable water quality requirements (strict and similar to WHO and USEPA)
   TDS

protection of the environment and the Dead Sea (minimization of residuals)
   reliability of the design and facilitation of future expansion.

Raw Water
Flows to the plant
The plant is fed from three main sources of water having a total capacity of 60 million
m3/year. The maximum raw water flow to be admitted to the plant is 55 million m3/year. Each
source is contributing to the total flow according to the percentages below (so called “design
ratios” in the contract documents)(Table 1).
                         Table 1. Design source water composition.
                                     Capacity (million       Corrected flow for 55
                                           m3/day)                million m3/day
                 Zara Springs                 7                 6.4          11.7%
                 Wadi Mujib                  30                27.5          50.0%
             Wadi (Zarqa) Ma'in              23                21.1          38.3%
                     Total                   60                         55

Source Water Characteristics
The main characteristics of this combined raw water can be summarized as follows:
   brackish with an average salinity of 1,500 mg/l (TDS)
    low turbidity (under 10 NTU) predominantly with excursions during rainfall events to >
      40 NTU
   large seasonal water temperature fluctuation (from 15 to 45°C)
   significant concentrations of silica and strontium and substantial tendency to fouling (SDI
      > 20, UV/TOC ratio = 2.2)
     risk of contamination of the Wadi Ma’In Zarqa river by wastewater due to Madaba
      (nearby town
   with 80,000 inhabitants) and run-off from storm events
   bacteriological contamination (E-coliform about 3200 / 100 ml)
From an individual perspective, the Zara Spring source (11.7% of combined flow) has the
highest temperature (average near 40 C) and highest maximum silica concentration (40.12
mg/l). The Wadi Mujib source (50% of the combined flow) has highest pH, TSS (turbidity),
and iron. The Wadi (Zarqa) Ma’in (38.3% of the combined flow) has easily the highest TDS
(average 1706 mg/l, maximum 1980 mg/l) and also the highest average silica and strontium
concentrations.
The most pertinent raw water parameters for the combined source waters are summarized in
Table 2 below. These values are from the original project specification. The significant
variation due to seasonal or climatic conditions is very apparent for key RO design parameters
such as temperature, salinity, silica, and strontium. The occasional severe spikes in raw water
turbidity and fluctuation in UV absorbance point to the need for an effective pretreatment.

Table 2. Raw Water Quality, Average and Maximum Values

                                                                   Maximum Value
     Parameter              Unit            Range        Average Combined   Worst
                                                                  Water   Resource
Salinity (TDS)             mg/L          1,092 – 1,980    1,487    1,685   1,980**
Temperature
Pre-treatment                °C             15 – 45        27.5                45
Reverse Osmosis                             20 - 40                            40
Barium                     mg/L          0.051 – 0.086     0.065             0.086
Strontium                  mg/L          1.84 – 14.52      6.32              14.52
Boron                      µg/L          < 100 – 1,000      200              1.000
Turbidity                  NTU             1.7 – 180         7                180
Silt Density Index                                                           > 20
Suspended solids           mg/L             1 – 550         15               550
TOC – Total
                          mg C/L           0.1 – 0.8        0.6               1.4
Organic Carbon
UV Absorption at
                            m-1           0.24 – 2.14      2.14              2.14
254 mm
UV / TOC                      -

Treatability Tests
Coagulants, coagulation pH, and flocculants were screened to determine the optimum
treatment. Both alum and ferric salts worked effectively, with the optimum pH range being
6.8 to 7.2 (sulphuric acid was added at approximately 25 mg/l to obtain this coagulation pH.
Optimum coagulant dosages were typically 15-20 mg/l for alum and ferric sulphate and 8-12
mg/l for ferric chloride. Optimum coagulant conditions were determined based on settled
water turbidity, filtered turbidity, filtered color, total and filtered iron, manganese, and
aluminium, and organic residuals. A coagulation time of 2 minutes was quite adequate,
particularly owing to the high temperature of the raw water. A high molecular weight, low
charge density anionic flocculent was utilized at a dosage of 0.1 mg/l. Settling and sludge
cohesion tests were done to confirm the proper design velocity for the sludge blanket clarifier.
Filtration test were also performed on settled water to confirm the SDI value after filtration
and the filtration media choice.

Optimum Pretreatment Process
Based on this work, an accurate determination of the various source water qualities and
variations were determined. Treatability and pilot studies concluded that the best
pretreatment consisted of:
   Prechlorination (shock, as necessary)
   Acidification to obtain optimum coagulation pH (6.8-7.2) and to minimize indigenous
   aluminum residual; addition of KMnO4 as necessary when presence of manganese
    Coagulation with ferric chloride (8-12 mg/l), alum (15-20 mg/l) or ferric sulfate (15-20
   mg/l)
   Flocculation with 0.1 mg/l anionic flocculant
    Clarification with an upflow solids contact sludge blanket clarifier– upflow velocity 7
   m/hr
   Post-coagulation (0.3 – 0.6 mg/l as Fe)
   Dual media filtration (sand & anthracite at specific depths and effective size)

Plant Design
The overall process design was based on the following key objectives:
   Achievement of the required effluent standards and requirements
   Maximum reliability of the overall process
   Optimized capital and operating cost
   Maximum water recovery and minimum wastewater discharge
   Flexibility in terms of process adaptability to widely varying influent conditions and in
   terms of potential future plant expansion
The required net capacity of the plant is 128,767 m3/day (47 million m3/day) based on 24 hour
production under the maximum or worst case influent water quality. The plant was also
required to have sufficient flexibility to operate at the minimum projected demand of 26
million m3/day. The maximum and minimum capacities at the various stages from the raw
water pumping station to the treated water pumping station were designed to meet those
criteria.
Pretreatment Design
The primary objectives of the pretreatment system are (1) 3-log removal of Giardia and
Cryptosporidium and 2-log removal of viruses and (2) production of a consistently high

quality RO feedwater (SDI

Additionally, the pretreatment in association with the RO provides the assuredness of
multiple barriers to microbiological contaminants: (1) sedimentation and filtration, (2)
membrane (RO) filtration, and (3) chlorine disinfection.

                     Table 3. Projected Pretreated Water Characteristics
                                                 Maximum value for Maximum value for
   Characteristics        Unit      Average
                                                  combined water    the worst source
Calcium as Ca             mg/l         110             120
Magnesium as Mg           mg/l          43              49
Sodium as Na              mg/l         310             340
Potassium as K            mg/l          43              46
Strontium as Sr           µg/l         2.5             6.32              14.52
Barium as Ba              mg/l        0.065           0.082              0.086
Bicarbonates as           mg/l         122             122
HCO3
Sulfates as SO4           mg/l         260                260
Chlorides as Cl           mg/l         575               661.5
Fluorides as F            mg/l         0.5                0.5
Nitrates as NO3           mg/l          4                  4
Silica as SiO2            mg/l        18.4               26.26                   40.12
Salinity TDS              mg/l        1,494              1,685                   1,850
pH                         -          6.60               6.60
Carbon dioxide as         mg/l          50                 52
CO2
Temperature                °C         20-40              20-40                   20-40
SDI (Silt Density           -

Variable RO Feedwater Quality - Raw water originates from three (3) different sources, the
flow rates and characteristics of which are subject to variations. Table 4 which follows
provides detail on the average values of raw water characteristics (does not account for
pretreatment) calculated as 11.7% the average analysis of Zara Springs, plus 50.0% the
average analysis of Wadi Mujib, plus 38.3% the average analysis of Wadi Ma’in. The average
analysis is shown in the column “Combined average water quality”. The “combined worst
water quality” referred to in Table 6 reflects the blending to the specified ratios of the worst
analysis of each source water. The key sizing (limiting) parameters for the RO design are
silica content, TDS and temperature. Thus, “worst” can be interpreted as worst for TDS or
worst for Silica content.
In fact no easy link can be detected between the silica content and the other sizing parameters
– temperature, TDS, and seasonal/climatic impacted water quality (dry, rainy seasons, etc).
Silica varies independently from the other parameters. All cases must be studied. However the
contracted guarantee is to achieve 90% recovery at average combined water characteristics
(18.6 mg/l of silica), and 85% recovery at worst combined water characteristics (26.3 mg/l of
silica).
Recovery Rates - The overall recovery rate is dependent upon (1) pretreatment water losses
(projected to be 0.5% of raw water flow or up to 0.275 million m3/year), (2) salt rejection, (3)
solubility limits of salts (barium and silica are the limiting factors in this design), (4)
pretreatment efficiency and cartridge filtration (5 µm selected), and (5) antiscalant selection
and dosage to eliminate scaling risk for the membranes. Detailed calculations show that the
plant recovery is not affected by the raw water salinity provided it remains within the
specified design value (i.e. below 1980 mg/L). The only operating parameter that has an
impact on the water recovery is the silica content (in conjunction with temperature). The
recovery rate is:
   90% when raw water characteristics represent average values.
   85% when the raw water characteristics represent the combined extreme values from
   individual sources after mixing at the design ratios (26.26 mg/L of SiO2).
This curve is used for controlling the RO skids recovery based on a silica measurement using
an on-line silica analyzer to monitor the pretreated water. The percentage from silica
saturation concentration is between 55% (at 40°C) and 78% (at 20°C) in most cases (from
90% down to 85%).
Antiscaling agent – Due to the significant risk of scaling imposed by the high and variable
silica concentrations in the some of the source waters, an antiscaling agent will be employed
to mitigate the risk of silica scaling. The antiscaling agent dosing rate is related to the silica
content of the raw water (thus the recovery rate) as well as the water temperature (increased
silica scaling risk at low temperature).
Post-Treatment
The RO permeate is blended with a portion of pretreated water (247 m3/hr or about 5% of the
total plant production) since the RO design meets minimum recovery at all conditions of
temperature and TDS. This pretreated portion is disinfected with UV at a dosage of 40
mJ/cm to ensure necessary microbial inactivation.

Table 4. RO Feedwater Quality Parameters
                                              Combined                   Combined worst Combined worst water
                                            average water                water quality (for quality (for SiO2)
                                               quality                         TDS)
Temperature                 °C                 20 to 40                      20 to 40            20 to 40
pH                           -                   8.0                            8.0                 7.9
TDS                         mg/l                1475                          1663.1              1571.0
TSS                         mg/l                  65                            13.1                90.1
boron                       mg/l                 0.22                           0.22               0.22
calcium                     mg/l                 116                           121.8               115.0
magnesium                   mg/l                 42.2                           38.0                45.0
sodium                      mg/l                 312                           344.3               332.1
potassium                   mg/l                 32.5                           30.6                30.8
phosphate total             mg/l                 0.16                           0.05               0.04
nitrate                     mg/l                 3.96                            2.0                 2.8
sulfate                     mg/l                 199                           211.0               232.6
fluoride                    mg/l                 0.47                            0.5                 0.8
chloride                    mg/l                 577                           629.2               572.6
bicarbonate                 mg/l                 190                           209.0               198.5
aluminium                   mg/l                 0.14                           0.14                0.1
barium      (4)             mg/l

Water Recovery and Wastewater / Sludge Treatment
In addition to the main treatment train which includes the clarification, filtration, and reverse
osmosis, the filter backwash water and clarifier sludge blowdown is directed to a clarifier
thickener. Approximately 12,000 to 15,000 m3/day supernatant is recovered and treated via
UV disinfection (80 mJ/cm) to ensure proper microbial removal / inactivation efficiency and
recirculated to the plant inlet.
In order to protect the environment and the Dead Sea, the pretreatment sludge (from the
recirculation clarifier) is sent to drying lagoons. The major part of the suspended solids and
their pollutants (especially, microbiological contaminants) will be kept in the sludge in the
bottom of the drying lagoons. Only the reverse osmosis brine and the clear supernatant from
the lagoons will discharged by gravity to the Dead Sea. Therefore, the total average water
loss is just over 15,000 m3/day.

Conclusions
The Wadi Ma’in, Zara, and Mujib Water Treatment at 47 million m3/day (34 MGD) is one of
the larger brackish water RO plants in the world. The design was conceptualized, based on
strict treated water requirements and substantially varying multiple raw water sources, with
substantial emphasis on efficiency and flexibility.
The design of the system meets all water quality requirements of the project:
   all Jordanian potable water quality requirements
   TDS

Figure 2. Process flow diagram of the entire treatment plant design