CITY OF BEVERLY HILLS BEVERLY H I ILS PUBLIC WORKS DEPARTMENT MEMORANDUM TO: Public Works Commission FROM:

Transcription

1 BEVERLY H I ILS CITY OF BEVERLY HILLS PUBLIC WORKS DEPARTMENT MEMORANDUM TO: FROM: Public Works Commission Gil Borboa, Assistant Director of Public Works Vince Damasse, Water Resources Manager DATE: SUBJECT: ATTACHMENTS: March 8, 218 Hollywood Basin Wells Pre-Treatment Testing Update Reporting Period February 1 to February 28, Test Work Plan Progress Flow Diagram RECOMMENDATION Staff recommends that the Public Works Commission receive and file this report. DISCUSSION Following the discovery and identification of the changed water quality conditions in the Hollywood Basin wells, staff contracted with Carollo Engineers (Carollo) to begin the next phase of investigation to determine pre-treatment options at the WTP. The pre-treatment options are part of a multi-pronged approach to evaluate potential pre-treatment options, conduct well rehabilitation, and explore blending options to address the water quality issues of iron sulfide, sanding, and higher than historical Manganese levels in groundwater. The process by which pre-treatment alternatives are being investigated for each of the aforementioned water quality constituents is included in the attached process flow chart. The flow chart provides a graphical representation of Carollo s pre-treatment approach for each constituent. Each of the constituents of concern has flow charts indicating potential bench scale and/or pre-treatment pilot options that may be utilized in a pre-described sequence to attempt to mitigate a particular water quality issue. The areas on the flowchart indicated in light grey, represent testing work options that have been completed to date while the blue colored represent work in progress that was either started or conducted and is in-progress for the reporting period. The attached flow chart was updated at the end of this reporting period (February February 28, 218) to reflect current progress. ito areas During this reporting period, a blend of the three operating Hollywood Basin Wells (Wells 4, 5 and 6) was tested with a sequence of pre-treatment processes; the Forsta sand separator, the Filtronics oxidation and filtration pilot, followed by the single-element RO pilot. The following summarizes the findings of each constituent of concern. Sand/Iron Sulfide: The positive results from past months for sand and iron sulfide removal were again replicated during this reporting period. Staff observed small amounts of incoming sand and iron sulfide

2 particles in the Rossum sand testers but these constituents were all removed at the end of the Filtronics pre-treatment process prior to entering the RO pilot equipment. In addition, for all water samples that were sent to an external laboratory during testing, optical micrographs of the Filtronics effluent was described to contain very few particles, almost clear. The reduction in particles entering the RO pilot skid is beneficial because this would prevent the clogging of membranes, the abrupt increase in differential pressure (and resultant shutdowns), and the extremely short runtimes. RO pilot performance is summarized later in the report. Iron/Manganese/Arsenic/Hydrogen Sulfide: During the reporting period, iron, manganese and hydrogen sulfide were all removed to nondetect levels except for the sample collected on February 16, 218. This sample was collected shortly after an electrical power outage had occurred at the water treatment plant, causing insufficient chemical dosing. 2. WeH4 Raw Iron WeN 6 Raw Iron 18. We 5 Raw Iron Hollywood Blend Raw Iron 16. Effluent Iron 14..S 12, 1. * Iron Secondary MCI: 3 ppb ,.. **, e #sa..., /11 12/1 12/21 1/1 1/ Iron removal

3 8, Secondary MCL Hollywood Blend Raw Manganese We 5 Raw Manganese Effluent Manganese 1. 9 Department of Drinking Water s (DDW) permit level. Regardless, the Filtronics pre-treatment rest (i.e. non-detect of Arsenic in RO effluent (permeate)). process was able to remove around 5% of the Arsenic and the RO pilot system removed the For Arsenic, due to the blending of the wells, influent concentrations were already below the Hydrogen Sulfide removal o.oo...* z 3 4 Holtywood Blend Raw Hydrogen Sulfide 5 Wet 6 Raw Hydrogen Sulfide Manganese removal... I. *,...,,, a6 a, 5.ea, C) 1. 11/ /21 1/1 1/ Effluent Hydrogen Sulfide Taste/Odor Threshold E a, V U) / /7 1/27 2/16 We6RawManganese Wet 4 Raw Manganese

4 35. - DOW Permit Limit 4. - MCL Effluent Arsenic 45 Hollywood Blend Raw Arsenic Well 5 Raw Arsenic Silica Data Silica Feed Permeate Silica 2, 25. 3o 35, Reverse Osmosis: hardness. RO performance. RO permeate (effluent) samples all had non-detect levels of TDS, silica, and The Filtronics effluent was then pumped to the single element RO pilot skid to simulate full-scale Arsenic removal.. * o. 3. U, /11 12/1 12/21 1/1 1/ Cl) 215 2/7 2/9 2/ / Well 6 Raw Arsenic so o Well 4 I (3 NsenIc

5 6. 5. normalized salt passage, the ideal result would be for the data points to resemble a straight line, permeate water quality) indicate good RO performance. For normalized permeate flow and differential pressures were also monitored closely by staff. The plots below (combined with the RO operating parameters such as normalized permeate flow, normalized salt passage, and Hardness Data /11 2/13 2/15 2/17. I 5. Permeate Hardness Feed Hardness. 1. U, E -J o 2. In TDS Data 2/5 2/7 2/9 2/11 2/13 2/f 5 2/17,, 1. Permeate TDS 2. Feed TDS ,

6 , September 217 is plotted on the same graph. Results indicate that the pretreatment system has a positive impact on the differential pressure of the RO system. possible. As a reference, the baseline RO DP data with no pretreatment collected during For differential pressure (DP), it is essential to keep DP consistent and low for as long as Normalized Salt Passage Operating Time (days) %...+.ø*..., % a 3.% 4.% 5.% 6.% o 7.% 8.% 9.% 1.% Normalized Permeate Flow Operation (Days) e..... =..... S testing. which indicates minimal membrane fouling. This was observed throughout the duration of

7 Base{me status update and will be available for any questions. Staff has received requests from the Commission for a private tour of the pilot system and can be available upon request for tours as needed. Carollo and staff will present a brief project equipment being installed and tested during February / March 218. Depending on when the memorandum prepared in May/June 218. Maple Yard wells come online, pilot testing will continue throughout April with the technical The Maple Yard Wells pump/motor equipment arrived in late February 218 with the pumping Filtronics system s capability for removing the highest levels of Manganese. treatment system, and RD pilot systems on the Maple Yard Wells, which would test the The final phase of testing includes operating the sand separator, Filtronics iron/manganese pre Next Steps: Operation (Days) e e a 4... I,, $ a, a, 8 a, I.. C Prcteatrnent