IWC 1 1

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72 nd ANNUAL INTERNATIONAL W ATER C ONFERENCE (IWC) 

# RECOVERY AND RECYCLING OF INDUSTRIAL SIDE

- STREAM WASTEWATER

Michael Chan, P.E. Duraflow, LLC Tewksbury, MA

K EYWORDS : Industrial wastewater, side

- stream wastewater, difficult

- to

- treat, recycle, reuse, chemica l softening, pre

- treatment, membrane, microfiltration, reverse osmosis

ABSTRACT

M ost industrial operations generate a substantial quantity of “side

- stream” wastes. These streams are characterized by their high concentrations and difficult

- to

- treat prope rty

. Recent studies have identified side

- stream wastes as a major cause of perfor mance problem to treatment operation s

. As the national water scarcity crisis escalat es , industries have started looking into recycling of the less desirable water sources as a long

- term sustainable solution to the problem. This presentation shall explore the technical challenges associated with side

- stream s management

.

INTRODUCTION It is well documented that water is a

scarce resource in many parts of the world including in the U.S . In som e areas water availability is the key issue while in other s , water quality is the major problem . Some locations , unfortunately, have to cope with both quality and quantity issues . In response to these growing concerns , industry has been challenged to find ways to utilize poorer quality water , such as the side

- stream wastes, which in general is not being considered a viable source in the past

. For most industrial water and wastewater treatment operations, a substantial quantity of side

- stream wastes is generated from t he manufacturing and water/wastewater treatment processes as by

products of the operations

. These streams are characterized by high concentrations in total dissolved solids (TDS) , suspended particles, difficult

- to

- treat chemicals and organic substances.

SID ESTREAM SOURCES As shown in Figure 1

, s ide

- stream wastes are generated from three primary sources: (1) Manufacturing operations, (2) Process water supply treatment operations, and (3) Wastewater treatment or recycling operations. The types of side

- streams fr om these sources vary according to the industry, production processes, technology employed and method of operation. As a general characteristic, side

- streams have high instantaneously flow rate but small average volume relative to the main stream, and t hey

co ntain high concentration s of various contaminants as indicated in Table 1.IWC 1 1

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Table 1

– Side

- stream Contaminants

Side

- stream Contaminants

Reverse Osmosis Brine High TDS, hardness, silica, and metals Filter/Screen B ackwash High TSS Cooling Tower Blowdown High TDS, TSS, hardness, silica, and organic Equipment Wash

- down Complex cleaning chemicals, and trace heavy metals Scrubber Blow

- down High chloride, sulfate, heavy metals and organic Ion Exchange Regeneration W astes High TDS, TSS, hardness
Boiler Blowdown High TDS, metals and complex chemicals

IMPACT ON WWTP Most of the traditional wastewater treatment plant (WWTP) combines the side

stream wastes with the main wastewater stream for treatment. It was reported that the side

- st ream wastes cause significant interferences, mal functions and damages, in many cases, to the treatment operation. The degree of impact on the WWTP will depend largely on factors such as the flow volume, surge frequency, chemical characteristic, TSS concen tration

, and mixing ratio and blending method for the side

- stream s . The following examples were documented for some of the major impacts observed and reported

.

 Foul the RO membrane pre

- maturely and cleaning the membrane is difficult.

 Foul or bind the activated carbon and

san d filter medium , and increas e the backwash frequency and volume.

 Interfer e with the coagulation reaction and cause discharge compliance issues

.

 Caus e settling difficulties in clarifier resulting in carry

- over of pin flocs in the overfl ow

.

 Induce watery sludge cake generated from the de

- watering process.

S IDE

- STREAM R ECYCLING TECHNOLOGY Reverse Osmosis (RO)

- RO membranes are designed for removal of dissolved solids with high efficiency , but adversely affected or fouled by suspe nded solids, colloidal material or scale

. Common examples of such foulants are calcium precipitates, metal oxides, colloidal silica and various organics. Industrial side

- stream wastewater typically contains most, if not all, of these fouling substances. Once fouled

, limited by its membrane material properties, only mild cleaning chemicals such as citric acid and detergent can be used to restore the flux . Stronger or more effective cleaning Process Water Treatment

Production Operation

W W Treatment or Recycle

Figure 1

– Industrial Side

- stream Sources Industrial S ide

- streams

 RO Brine (Reject)

 Filter/Screen Back wash

 IX Regenerant

 Bo i l er Blowdown

 De

- watering Filtrate / Centrate

 Cooling Tower Blowdown

 Plant & Equip

. Washdown

 Scrubber Blowdown Water Recycle Water SupplyIWC 1 1

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chemicals, such as sulfuric acid, hydrochloric acid, bleach, and peroxide

can not be applied as they will cause irreversible da mag es to the RO membrane s

. In wastewater recycling applications, RO

can rarely function independently without any protection from the fouling materials. Appropriate pretreatment must be provided to achieve stable performance of RO membranes.

Micro filtration ( MF )

– Certain MF products ha ve demonstrated the ability to handle concentrated wastewater and significantly reduce membrane fouling to provide stable, predictable RO performance . The success of MF for this application can be attributed to the following k ey reasons:

 M F membrane is designed to remove suspended solids and colloidal particles (RO foulants)

. Some of the MF products, such as the one with tubular configuration, can handle very high TSS of >5

, 000 mg/L in the influent.

 MF membrane can be made of a variety of polymeric materials, including PVDF, which exhibit strong resistance to concentrated chemicals. As a result, the membrane can be cleaned with mineral acids, oxidizers (bleach, peroxide), caustic and selected organic solvents for removal of di fferent persistent fouling elements, both inorganic and organic, which are difficult to be removed with weak cleaning chemicals.

 MF f iltrat ion produces a quality product water stream with NTU (<1.0) and SDI (<3.0) values in full compliance with the feed wa ter criteria specified by all RO manufacturers.

 The chemical or physical characteristic of the foulants in the wastewater can be converted into particles suitable for removal by M F filtration

.  The MF can be designed to remove regulated contaminants in the side

stream wastes and make the RO reject more manageable for recovery or discharge.

C hemical pre

- treatment plays a key role in membrane

- based treatment or recycle. Properly designed and controlled chemistry mitigate s the effects of the fouling components on membrane because it induced a change in the characteristics of the foulants. The principle pre

- treatment chemistries for different contaminants are presented in Table 2.

Table 2

– Pre

- treatment Chemistry

Examples
Contaminants MF Pre

- treatment Chemistry

Hardness (Ca & Mg)  Chemical softening

- Lime

& soda ash Heavy Metals  Hydroxide precipitation

–

Caustic/lime

 Sulfide precipitation

– Sodium sulfide

 Organo

- sulfur precipitation

– Sodium Dithiocarbamate (DTC)
Fluoride  De

- fluoridation

–

Calcium/aluminum sal ts
Sulfate  Sulfate precipitation

- lime

and aluminum salt.
Silica  Chemical adsorption

–

Magnesium salt
Oil & Grease  Adsorption

– Lime /

activated carbon

 Acid Cracking

– Sulfuric acid Organic  Adsorption

– Lime /

activated carbon

 Coagulation

– Aluminum/ iron salts

 Oxidation destruction

– Bleach / PeroxideIWC 1 1

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C ASE S TUDY S IDE

- STREAM S RECYCLING Project Data Plant Type/Location An a utomotive c omponents m anufacturers located in Mexico

. Backgroun d (1) There w as s evere shortage of quality
water a round the plant site

. (2) Performa nce of the main WW PT plant was unstable and subject to frequent upset s due to high variation of the influent characteristic

. Project Objective Segregat e the difficult

- to

- treat side

- streams, specifically the cooling tower blowdown and RO brine, for water recycl ing and improvement of the central WWTP
ope ration

. Years of Operation Over 8 years

. Side

- stream Flow 1 00 to 150 GPM

. Recycle Concept Selected side

- streams, RO brine, cooling tower blowdown and others from the production process es and main wastewater treatment plant are directed to an equalizatio n tank. The process starts with chemical softening / coagulation and followed by microfiltration and RO. The RO permeate is returned to the cooling tower for

reuse , and the reject stream is discharge to

an on

- site evaporation pond for de

- watering

. Design Considerati on s The side

- streams contain a variety of membrane f

oulants including h ardness (Calcium and Magnesium), s ilica, o rganic (Anti

- scalant & Dispersants) and total suspended solids (TSS) . Fouling control plays a critical role in the success of operating a membrane

- based recycl ing system. The Fouling Mitigation Technique (FMT) employed consist s of Chemical Softening for c onvert ing all foulants into compatible forms followed by MF for separation of the resulting suspended solids.

The MF membranes employed in this installation are manufa ctured in a tubular configuration designed to handl e high solid concentration. The membranes, made of PVDF, are cast on the surface of porous polymeric tubes to produce a nominal pore size of 0.1 micron. Figure 2 illustrate s the MF membrane modules install ed in the system. Bleach and hydrochloric acid are typically used for membrane cleaning.

The chemically pre

- treated wastewater is processed through the MF membrane modules designed for separation of the precipitates from water. The wastewater is pumped at a velocity of 12

– 15 ft/sec through the membrane modules connected in series as shown in Figure 3 . The turbulent flow, parallel to the membrane surface, produces a high

- shear scrubbing action which minimizes deposition of solids on the membran e surface. During operation, filtrate permeates through the membrane, while the suspended solids retained in the

re

- circulation loop are periodically purged for further de

- watering. An automatic back

pulse mechanism provide s surface cleaning by periodical ly reversing the filtrate flow direction. The MF has been operated with an average flux of 300 GFD. The entire
treatment process is depicted in Figure 4

. Figure 2 MF M odule End View Figure 3 MF System ConfigurationIWC 1 1

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Membrane P rocess P erformance Data The removal efficienc y for selected elements in the MF filtrate and RO permeate is presented in Table 3.

Table 3

– Selected Membrane Process Performance Data

Selected Elements Influent

(mg/L as ion) MF Filtrate

(mg/L as ion) RO Permeate

(mg/L as ion)

Ca 150

– 300 < 35 .0 <1.0
Mg 100

– 250 < 5 .0 <0.5

SiO 2 100

- 200 <10.0 < 4 .0

Na 900

– 1, 200 <1200 <60

SO 4 1,000

– 1, 500 <150 0 < 40

Cl 500

- 900 <900 <45

TSS 250

– 1, 500 <1.0 ND

TDS 3

, 000

– 4, 000 <4,000 <200

SDI

---- < 2 .0

----

Figure 4

– Simplified Side

- stream Wastewater Recycling Process Flow Diagram

Tub ular Microfultration Reverse Osmosis Manufacturing Plant Side

- stream EQ

 Process Water RO Brine

 Cooling Tower Blowdown

 Filter/Screen Backwash

 De

- watering Filtrate

 Plant & Equip. Washdown Two

- Stage Chemical Softening & Coagulation

Central Waste water Treatment & Recycling Plant RO Permeate To Cooling Tower Softening Coagulant s Chemicals Selected Sidestreams

Effluent Discharge

RO Reject t o Evaporation Pond Sludge Slurry to Central De

- watering Side

- stream Recycle System Main WW Stream Recycle WaterIWC 1 1

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C ONCLUSION Side

- stream wastewater is known to cause adverse impact to the operation and performance of a conventional wastewater treatment system. Most of the side

- streams can be clearly defined , but for large industrial plant operations, so me of them will r equire thorough site survey to track and identify

. The removal of side

- stream wastes from the main wastewater stream has
a two

- fold advantage: (1) Improve and optimize the performance of the main treatment system, and (2) maximize the in

house re source available for recycle and reuse. Membrane based technolog y (MF/RO) is proven as a technically viable approach. Chemical pre

- treatment that transforms wastewater into membrane

compatible form provides the needed flexibility to cope with the complicated and fa st

- changing side

- streams chemistry

. To

as sure a successful side

- stream control project from initial desi g n to final operation,

c areful evaluation of potential sources of reuse water is needed and detailed treatment processes must be tailored to the site speci fic needs of a particular plant. R EFERENCE 1. Cheryan, Munir, 1998, Ultrafiltration and Microfiltration Handbook, 2 nd edition, CRC Press, Boca Raton, Florida, pp. 237

– 254.

2. Duraflow, 2005

– 2011

, Internal T echnical Files

.

3. EPA, December 1985, Sidestream s in Advanc ed Wastewater Treatment Plants: Problems and Rem e dies, pp. 3

- 4.

4. Hydranautics, January 2001, Pre

- t reat ment , Technical Service Bulletin

.