Proceedings of Western Dredging Association and Texas A&M University Center for Dredging Studies' "Dredging Summit and Expo 2015"

ELECTROCOAGULATION (EC) AND CHITOSAN ENHANCED SAND (CESF) TREATMENT TECHNOLOGIES FOR DREDGE RETURN WATER: TWO CASE STUDIES ON THE LOWER DUWAMISH WATERWAY IN SEATTLE, WASHINGTON

L.M. Doty1

ABSTRACT Thirteen years ago, the Lower Duwamish Waterway in Seattle, Washington was designated as a superfund site due to contamination with , PCBs/cPAHs, and dioxins/furans, the result of heavy industrial use in the area over the last century. Comprehensive clean-up is still a few years out, however the Environmental Protection Agency (EPA) designated 29 acres of “hot spots” that posed enough threat to human and environmental health to warrant Early Action.

Two specific Early Action Areas (EAA) conducted environmental dredging activities from 2013 to 2014. Due to contamination levels, specifically heavy metals and PCBs, traditional methods of on-barge dewatering were not allowed. Site 1 had limited upland real estate and implemented an Electrocoagulation (EC) treatment train. Geotubes with , an established dewatering technique, was considered for Site 1, however potential toxicity of the polymers and lack of sufficient real estate made this option unfeasible. Site 2 had no upland real estate and deployed a barge mounted Chitosan Enhanced Sand Filtration (CESF) system. Both the EC and CESF treatment technologies carry a General Use Level Designation (GULD) granted by the Washington State Department of Ecology for turbidity removal on construction sites. The GULD status of these technologies helped streamline the permitting approval process.

Site 1 operated for 48 days without any water violations, discharging 6,300,000 gallons of treated water back to the Duwamish River. Site 2 operated for 45 days without any water quality violations, discharging over 5,000,000 gallons of treated water back to the Duwamish River. The laydown areas required were approximately 5000sf and required no ground disturbance, as all treatment train components were mobile. For Site 1, this equates to a nine- fold reduction is land use compared to the Geotube approach. No land was available for Site 2, so temporary equipment on flexi-floats was the only alternative.

As presented and discussed in the Site 1 and Site 2 case studies, EC and CESF provide reduced footprint options for treating contaminated return water for direct discharge to surface waters. Both technologies produced effluent with water quality levels well below discharge limits. In addition both technologies have GULD approvals and are considered non-toxic which eliminates the need for ongoing toxicity screening and streamlines the approval process.

Keywords: dredge return water, contamination, remediation, superfund, water treatment, chitosan enhanced sand filtration, electro-coagulation, CESF, EC, PCBs

1 CPSWQ/CPESC, Regulatory & National Construction Manager, Water Tectonics, Inc, 6900 Merrill Creek Parkway, Suite C, Everett, Washington 98203, USA, T: 425-349-4200, Fax: 425-349-4890, Email: [email protected].

176 Proceedings of Western Dredging Association and Texas A&M University Center for Dredging Studies' "Dredging Summit and Expo 2015"

INTRODUCTION The Lower Duwamish Waterway (LDW) Superfund Site is the last five mile stretch of the Duwamish River before it empties into Elliot Bay at Harbor Island in Seattle, Washington. Both sides of the LDW are heavily industrialized/commercial areas interspersed with the Georgetown and South Park neighborhoods of south Seattle.

Heavy industrial and maritime use over the last 100 years have left area soils, groundwater and river sediments contaminated with polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), dioxins/furans, arsenic and other heavy metals. In addition to commercial use, the Duwamish/Green river system is a traditional fishing ground for the Suquamish and Muckleshoot tribes and is also home to numerous fish hatcheries that release approximately 10 million juvenile salmon per year1. In 2001 the Environmental Protection Agency (EPA) placed the LDW on the Nation Priority List to protect and restore benthic organisms, resident fish populations and protect those who rely on these species as a food source. Following EPA’s listing, the Washington State Department of Ecology (WADOE) added the LDW to the Washington Hazardous Sites List in 2002.

Due to the size and complexity of the LDW, the final Record of Decision (ROD) for clean-up of the entire site was only recently finalized (November 2014). The ROD details the clean-up of approximately 177 acres and will involve dredging, capping and natural sedimentation with an estimated cost of $342 million2.

Prior to the issuance of the ROD, EPA identified six specific areas within the LDW site that posed immediate threats to the environment and human health. These are called Early Action Areas (EAAs). These EAAs had “hot spots” of contamination that in some cases were orders of magnitude higher than the surrounding LDW. Starting in 2011 EPA and WADOE entered into agreements with the owners and/or responsible parties to perform remedial actions. This paper discusses the remedial actions taken at the Boeing Plant 2 and Jorgensen EEAs, specifically dredge water return treatment during dredging activities. Locations are shown in Figure 1. Lower Duwamish Waterway superfund site and EEAs.Figure 1 below.

177 Proceedings of Western Dredging Association and Texas A&M University Center for Dredging Studies' "Dredging Summit and Expo 2015"

Figure 1. Lower Duwamish Waterway superfund site and EEAs.

178 Proceedings of Western Dredging Association and Texas A&M University Center for Dredging Studies' "Dredging Summit and Expo 2015"

DREDGE RETURN WATER TREATMENT Dredge return water management is highly variable from site to site and is largely dependent on the type of dredge project. Maintenance dredging will be less treatment intensive than a remediation project. Simple dewatering through the scuppers may be allowed on a maintenance project where extensive treatment with Geotubes® and coagulants may be required on environmental remediation projects. In some cases the water returned is not allowed to be discharged to the receiving water and must be discharged to the sanitary sewer. The pros and cons of these traditional methods are presented below in Table 1.

Table 1. Pros and cons of traditional dewatering processes. Method Pros Cons Sufficient treatment for Environmental/Remediation? Scuppers Easy, no additional cost Provides no treatment or No as barges come equipped only minimal treatment when filter fabric place over scuppers (large diameter soil particles). Geotube® Solids dewatering and Dewatering fluids may YES provided dewatering water treatment in a need further treatment fluids are properly treated. single step. If dewatered before discharge to material is clean, filled surface waters or sanitary bags can be used for sewer. Inconsistent bank stabilization or effluent water quality. other landscape feature. Large staging area High flow rate capacity. required for laydown and dewatering capture. Tubes are difficult to move once full. Sanitary Sewer For non-contaminated Not all jurisdictions YES provided dewatering sites minimal treatment is allow discharge. fluids are properly treated. typically required. Discharge may be subject to a per gallon fee. Some treatment likely required. Flow rates limited.

As remediation projects become more complex and space limited alternatives to traditional methods will be needed. Some alternatives can be borrowed from the upland construction industry where, particularly in Washington State, Active Treatment has been common for over a decade. Active Treatment Technologies Active Treatment involves pumping water, adding coagulants and filters to remove sediment and dissolved contaminants from a waste stream. In Washington State active treatment technologies have been extensively refined to treat turbid and pH impacted stormwater and groundwater in the construction industry. The practice became so prevalent that WADOE created a targeted assessment protocol, Chemical Technology Assessment Protocol – Ecology or CTAPE. The CTAPE process uses engineering evaluation as well as water quality performance and toxicity data to develop a General Use Level Designation (GULD) for a proposed technology. These approvals dictate how a coagulant or technology may be applied, what filtration must be used and how the system will be operated. The two GULD approved technologies used on the LDW EEA case studies are discussed in detail below.

Chitosan Enhanced Sand Filtration (CESF) Chitosan is a natural coagulant that promotes and facilitates the removal of particulate and colloidal solids (including clay and fine silt) from stormwater when used in conjunction with sand filtration. Chitosan is the only known naturally-occurring cationic (positively-charged) polysaccharide biopolymer. Chitosan Acetate is

179 Proceedings of Western Dredging Association and Texas A&M University Center for Dredging Studies' "Dredging Summit and Expo 2015" soluble at pH less than 7. When the pH increases above 8.0 the chitosan will precipitate out of solution & becomes inactive.

Figure 2. Molecular representation of chitosan acetate.

Chitosan promotes coagulation and flocculation of solids in storm/ground water waste stream. Coagulation is the process of destabilizing the predominately negative charge of particulate and colloidal eroded soil in stormwater. Sediment typically exhibits a net-negative charge in water, the negative charged particles stay dispersed in the water due to the effect of charge-to-charge repulsion. Chitosan acetate is positively charged and destabilizes the negative charge (Figure 2). Flocculation is a natural process of agglomeration of destabilized (coagulated) particles into larger particles typically referred to as flocculated solids or “flocs.” Making larger particles out of small particles into larger flocs which are heavier and settle quicker. The flocculated material is then removed by a combination of gravity settling and filtration resulting in water with significantly reduced turbidity.

The CESF treatment train consists of detention structures, pumps, piping, chemical metering devices, sand filter, water quality probes, automated values and programmable logic controller. The typical treatment train configuration is shown in Figure 3, and each step is discussed below.

KEY CO2 Injection Point pH Measurement Location

Turbidity Measurement Location

PRETREATMENT Chitosan Injection Point

P Detention Coagulation/Settling Pond/Tank/Vault Treatment Tank Connex P Sand Filter

Inflow Discharge from Site Off‐site

Figure 3. CESF treatment train.

Step 1 consists of the primary settling pond or tanks. The influent water is analyzed for pH by submersible pH probe if tank is used. The pH is lowered to an optimum reaction point by injecting carbon dioxide into a fine gas bubbler hose. The bubbler hose is held down by inert sand ballast built into the hose. The Carbon dioxide injection will be controlled by a set of pH probes linked to a solenoid control system. This system is connected to a

180 Proceedings of Western Dredging Association and Texas A&M University Center for Dredging Studies' "Dredging Summit and Expo 2015"

SC100 Hach controller that reads and adjusts the carbon dioxide feed rate duration. Detention provided by the pond/tank will allow for gravity settling of larger particles. Influent turbidity is read inline as the water enters the Chitosan Enhanced Treatment System Box (Box).

Step 2 consists of pretreatment when influent turbidity exceeds 600 ntu. If pretreatment is required, Chitosan is injected prior to the pump for initial turbidity reduction. The rate of dosage is decided via field jar testing by the operator. The water from the pretreatment tank(s) is then pumped through the CESF Box. The pretreatment tank(s) will need to be monitored for sludge build up. A maintenance program, based on physical inspection, will be required to remove the sludge on a regular basis.

Step 3 consists of the water (pre-treated or not) passing through the standard CESF system. Here, the influent pH and turbidity are monitored at a second injection point. Additional Chitosan is available for injection if needed. The function of the Chitosan in this stage is to convert particles smaller than 15 microns to particles larger than 20 microns so they can be removed by the sand filters. The water is sent through at least 50 feet of piping (to facilitate coagulation) before entering the sandfilter(s) which remove the flocculated particles.

In Step 4 the sandfilter removes particles that are 15-20 microns or larger from the treated effluent stream. The sandfilter will automatically backwash itself in order to avoid blinding at the interior upper level of the sandfilter bed. Automated backwash is initiated one pod at a time when the preset pressure differential is exceeded.

After sand filtration the treated water is sent back to the CESF box to monitor pH and turbidity. The PLC is set up to either discharge the water or to send it back to the source for reprocessing based on the real time water quality readings. This is necessary to ensure that pH and turbidity are in the correct range for discharge ensuring that no out of spec water is discharged. The system is also equipped with a flow meter that records the volume of water treated as well as the flow rate when operational. Effluent water quality data is logged in 15 minute increments as well as being instantaneously shown on the screen (Figure 4).

Figure 4. CESF water quality monitoring and PLC panels.

Electrocoagulation (EC) EC is a process that is combined with filtration to remove , heavy metals, emulsified oils, , and other contaminants from water. As water passes through the electrocoagulation cell, multiple reactions take place simultaneously. First, on the surface of the , a metal is driven into the water. Second, on the surface of the , water is hydrolyzed into hydrogen gas and hydroxyl groups. And third, electrons flow freely from the cathode to the anode which destabilizes surface charges on suspended solids and emulsified oils. As the reaction begins, metal complex with hydroxyl groups and form large flocs that include metals and other

181 Proceedings of Western Dredging Association and Texas A&M University Center for Dredging Studies' "Dredging Summit and Expo 2015" contaminants. Suspended solids and emulsified oils are readily entrained within the floc because of the destabilized surface charges. Finally, the hydrogen gas bubbles help to separate and lift the flocs (Figure 5). Depending on the application, the final solids separation step can be done using setttling tanks, media filtration, , and further selective polishing methods (granular activated carbon, orgaanno clay, resin, , etc).

Figure 5. Electrocoagulation reaction.

Like CESF, the EC treatment train consists of detention structures, pumps, piping, sand filter, water quality probes, automated values and programmable logic controller. The typical treatment train configuration is shown in Figure 6Figure 3, with each step further discussed below.

Figure 6. EC treatment train.

Step 1 consists of the primary settling pond or tanks. This will be the pump point for the EC system. Detention provided by the pond/tank will allow for gravity settling of larger particles. Depending on influent water quality, conductivity and pH may be adjusted in this step. The influent wateer is analyzed for pH by submersible pH probe if tank is used. Unlike CESF the EC process is not affected by high pH and so pH adjustment is only performed if necessary to meet discharge limits.

182 Proceedings of Western Dredging Association and Texas A&M University Center for Dredging Studies' "Dredging Summit and Expo 2015"

In Step 2 water is conveyed from the influent tank to the WaveIonics EC treatment system where it is distributed through a series of electrocoagulation treatment cells. As water leaves the treatment cells, fine particles and heavy metal precipitates begin to coagulate due to cationic particle charges and electron surplus causing ionic/covalent bonding and agglomeration (Figure 5). The WaveIonics unit contains all of the automated system controls for all phases of the treatment train.

In Step 3, treated water leaving the cells is directed to the clarification tank(s) where coagulated and precipitated material settles. The clarified water is then pumped to the sand filter which removes any remaining suspended solids and precipitated heavy metals that have not settled out of the water column due to specific gravity or particle size. Sand filtration in this application is a pressure driven system where water is passed through layers of granular media (sand, garnet, anthracite) to remove particulates down to 0.5 microns. Water leaving the sand filtration system is routed to the Water Quality Discharge Valve for analysis prior to discharge from the system.

The final step prior discharge is measuring water quality. Turbidity and pH in real-time and the PLC and automated discharge valve only allows discharge of effluent water that meets user-defined criteria. Non-compliant water is automatically returned to the detention pond/tank for re-treatment.

All system processes are controlled by the PLC/HMI system located in the treatment box. This system incorporates control and adjustment of all system processes to a single touch-screen user interface (Figure 7). The interface allows the operator to visualize system performance and operations and visualize quickly if there are any elements that require operator attention. In standard operation, the system is set to run automatically and send system alerts to operators via text or mobile phone.

Figure 7. EC water quality monitoring and PLC/HMI panels.

183 Proceedings of Western Dredging Association and Texas A&M University Center for Dredging Studies' "Dredging Summit and Expo 2015"

CASE STUDIES

Site 1 – Boeing Plant 2 EAA – Construction Season 1 The Boeing Plant 2 EEA was comprised of both shoreline improvements as well as dredging activities. Contaminants of concern aside from standard turbidity and pH were cadmium, chromium, copper lead mercury, silver zinc and PCBs. The contractor had originally planned to use Geotubes® to manage solids and treat dredge return watere . In discussions with EPA and WADOE there were concerns about the that was planned on being used with the Geotube® technology and the agencies stated tthat no polymeers were to be used on the project. The only alternatives were sanitary sewer or EC. The sanitary sewer infrastructure in the area would not support the volumes anticipated and would still require treatment. This option was ruled out. A 300 gpm EC treatment train was proposed and approved by the agencies due to the non-polymer nature and ability to precipitate dissolved metals as well as reduce turbidity/TSS. The core EC 300 gpm system was comprised of six detention tanks, EC control box, two settling tanks, redundant sand filters and conveyance pumps. The contractor added a rock box and triflow separator unit before the detention tanks feeding the EC box as well as bag filtration and granular activated carbon (GAC) for final polish after the EC system sand filters (Figure 8 and Figure 9). The 300gpm EC system footprint was approximately half of what was required for the proposed Geotube® system.

Figure 8. Boeing Plant 2 EC equipment photos.

Figure 9. Boeing Plant 2 EC equipment layout (final).

184 Proceedings of Western Dredging Association and Texas A&M University Center for Dredging Studies' "Dredging Summit and Expo 2015"

A total of 36,000 cy of material was dredged utilizing four sediment barges with capacities ranging from 350 to 650 tons. Barges were dewatered using a large pump with a maximum capacity of 1200gpm. Due to varying water volumes during cuts and barge transport times the water quality entering the detention tanks was highly variable. At times the dredge return water was 10-15% solids, a 10 fold increase from the design of 1-2% solids. This translates to influent turbidity values of over 6000ntu and at one point a measured TSS volume of 37,000mg/L. While the rock box and Triflow removed large debris they were not able to reduce the upfront sediment loading as expected. The excessive loading reduced available detention, produced sediment carry-over between tanks and ultimately resulted in frequent tank clean-outs. To combat the loading additional detention and settling tanks were added and all were re-plumbed to facilitate tank clean-out while the system was operational (isolation valves). A second 300gpm system was mobilized to increase throughput to 600gpm (Figure 9). When the second system was mobilized it was plumbed in parallel so that one system could be operating while the other was serviced. This allowed processing to continue during maintenance activities.

During the first construction season approximately 6,300,000 million gallons were treated and discharged back to the Duwamish meeting all water quality compliance criteria. Return water treatment system operations occurred over 54 days with only 8 days of limited operation and 6 days where operations were suspended to implement the required design changes. Dredge return water treatment costs for Construction Season 1 were after adjusting for experimental equipment and contract extensions for upland work were $0.038/gallon. This figure does not include any accumulated solids or media removal and disposal.

Construction Season 1 (north shoreline and dredge) was a working pilot in preparation for the larger and longer Season 2 work (south shoreline and dredge). Along with increasing detention tanks and EC throughput during Season 1, a Dissolved Air Floatation unit was briefly installed to determine if this method would provide better separation, which it did not. Lab scale settling tests were performed and a 90% reduction in TSS was observed after 45 minutes of settling. This critical design information as well as refinement of operational measures was incorporated into the design of the Season 2 system which was relocated to the south on a larger 2 acre parcel. In Season 2 the upfront detention tanks were replaced with an ecology block pond with >500,000 gallons of detention which allowed for >45 minutes of settling time prior to the EC treatment system. The post EC settling tanks were replaced with a circular 30,000 gallon clarifier followed by sand and carbon filtration. These changes, particularly the upfront detention, resulted in less loading with the highest influent turbidity reading of 110ntu, a 98% decrease in solids loading to the EC system from Season 1 to Season 2. Season 2 activities are scheduled to be complete this spring.

Site 2 – Jorgensen EAA The Jorgensen EEA is immediately south and upstream of the Boeing Plant 2 site. Remediation activities included 12,500 cy of dredging along with material placement for capping and shoreline removal and restoration. The main contaminant of concern were PCBs and since PCBs are strongly associated with soil particles, EPA and WADOE were confident that water quality goals could be met with a Chitosan Enhanced Sand Filtration system which is excellent at removing soil particles (turbidity/TSS) from water. The agencies were pleased with the performance of Advanced Treatment /GULD Approved Technologies on previous EEA clean-ups which facilitated the approval process.

There was no upland area available to stage the treatment system so the contractor Pacific Pile & Marine (PPM) chose to place the equipment on flexi-floats in the river Figure 10. Since the Dredge Return Water was never brought onshore the permitting authority was undefined and the treatment approval process was simplified.

185 Proceedings of Western Dredging Association and Texas A&M University Center for Dredging Studies' "Dredging Summit and Expo 2015"

Figure 10. Jorgensen EEA dredge return water CESF treatment system (Courtesy PPM).

Having learned from the operations at Boeing Plant 2 – Season 1, the Jorgensen system was sized to process double the anticipated daily average flow rate of 250 gpm. Doubling the capacity would enable the system processing rate to be slowed down should heavy loading occur. To prevent excessive loading PPM agreed to modify their sediment barges to create clean(er) pump points, the goal being prevention of pumping large volumes of solids. Creating this sump area and allowing for 45 minutes of settling on the barge prior to dewatering kept the return water turbidity within normal and easily treatable ranges. The Jorgensen system was comprised of four upfront detention tanks, two pretreatment tanks, CESF treatment box with all controls, redundant sand filters and GAC for TSCA work (Figure 11 and Figure 12).

Figure 11. Jorgensen CESF equipment layout.

186 Proceedings of Western Dredging Association and Texas A&M University Center for Dredging Studies' "Dredging Summit and Expo 2015"

Figure 12. Jorgensen PFD. The barge mounted CESF system was operational from July 9, 2014 to August 23, 2014 during which time 5,183,000 gallons of dredge return water was treated and discharged to the LDW, meeting all water quality requirements. The dredge return water treatment costs, not including accumulated sediment or media removal was $0.041/gallon.

CONCLUSIONS Active treatment technologies like EC and CESF are viable alternatives for dredge water return treatment particularly on environmental remediation sites. The success and ease of treatability was directly impacted by three design and operational parameters: 1) How cleanly the return water was pumped from the barge to the detention/treatment facilities. 2) How much settling time was provided prior to the coagulation step. 3) How much additional capacity was included in the system sizing.

Identifying the above factors during the Boeing Plant 2 – Construction Season 1, implementing solutions and repeating these findings on the Jorgensen project reinforces that with proper design and operational controls EC and CESF may be a better solution than traditional methods for contaminated return water treatment. The ease of implementation (little to no site prep, mobile equipment, modular nature), reduced footprint and consistent effluent water quality despite variable influent are all benefits over traditional methods. The WADOE GULD status of these two technologies allows for easier approval process with the agencies having jurisdiction. Over 5 million gallons of return water were treated at each site, for a total of 10 million gallons with an average cost of $0.0395/gallon.

REFERENCES

Anchor QEA, LLC (2013) “Water Quality Monitoring Plan Basis of Design Report Jorgensen Forge Early Action Area.” Prepared for the US EPA Region 10, Seattle, Washington. AMEC Environmental & Infrastructure, Inc. (2013) “2012-2013 Construction Season Completion Report Duwmaish Sediment Other Area nd Southwest Bank Corrective Measure and Habitat Project Boeing Plant 2 Seattle/Tukwila, Washington”. Prepared for The Boeing Company, Seattle, Washington. EPA Region 10. (2011) “Jorgensen Forge Comment on Proposed Cleanup” Website: http://yosemite.epa.gov/r10/cleanup.nsf/sites/lduwamish EPA. (2012) “NPL Site Narrative for Lower Duwamish Waterway” Website: http://www.epa.gov/superfund/sites/npl/nar1622.htm EPA Region 10. (2015) “Lower Duwamish Waterway Superfund Site” Website: http://yosemite.epa.gov/r10/cleanup.nsf/sites/lduwamish EPA Region 10. (2015) “Lower Duwamish Waterway Superfund Site” Website: http://yosemite.epa.gov/r10/cleanup.nsf/sites/lduwamish EPA Region 10. (2015) “Lower Duwamish Waterway Record of Decision Fact Sheet on the final Cleanup Plan” Website: http://www.epa.gov/region10/duwamish.html EPA Region 10. (2015) “Lower Duwamish Waterway Record of Decision Fact Sheet” Website: http://www.epa.gov/region10/duwamish.html

187 Proceedings of Western Dredging Association and Texas A&M University Center for Dredging Studies' "Dredging Summit and Expo 2015"

Mastin, B.J., Lebster, G.E., Salley, J.R. (2008) “Use of Geotube® Dewatering Containers in Environmental Dredging”.Website: http://www.gowatersolve.com/downloads/GeoAmericas_2008_Mastin_and_Lebster_Use_of_Geotube_De wat.pdf Mastin, B.J., Lebster, G.E., (2008) “Dewatering of Oil-Contaminated Dredge Residuals” WEDA XXVIII Water Solve, LLC Grand Rapids, MI Moffatt & Nichol (2008) “Capitol Lake Alternatives Analysis Dredging and Disposal” General Administration State of Washington. WADOE (2015) “Jorgensen Forge Corp” Toxics Clean-up Program. Website: https://fortress.wa.gov/ecy/gsp/Sitepage.aspx?csid=3689 WADOE (2015) “Lower Duwamish Water Way” Toxics Clean-up Program. Website: http://www.ecy.wa.gov/programs/tcp/sites_brochure/lower_duwamish/lower_duwamish_hp.html WADOE (2015) “Lower Duwamish Waterway Source control Investigation Early Action Area 4 Boeing/Jorgensen”. Website: http://www.ecy.wa.gov/programs/tcp/sites_brochure/lower_duwamish/sites/early_action_area_4/early_acti on_area_4.htm WADOE (2015) “General Use Level Designation for Erosion and Sediment Control for Chitosan-Enhanced Sand Filtration using 1% StormKlear® LiquiFloc™ chitosan acetate solution”. Website: http://www.ecy.wa.gov/programs/wq/stormwater/newtech/use_designations/LIQUIfloc1PCTguld.pdf WADOE (2011) “General Use Level Designation for Erosion and Sediment Control for Water Tectonics’ WaveIonics™ Electrocoagulation Subtractive Technology (ECST)”. Website: http://www.ecy.wa.gov/programs/wq/stormwater/newtech/use_designations/WTECCUD31008.pdf

CITATION Doty, L. “Electrocoagulation (EC) and chitosan enhanced sand filtration (CESF) treatment technologies for dredge return water: two case studies on the lower Duwamish waterway in Seattle, Washington,” Proceedings of the Western Dredging Association and Texas A&M University Center for Dredging Studies' "Dredging Summit and Expo 2015", Houston, Texas, USA, June 22-25, 2015.

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