-----Original Message-----
From: Ludwin, David [mailto:DLUDWIN@OCSD.COM]
Sent: Thursday, February 20, 2003 9:11 AM
To: Secondary Treatment Peer Review Panel
Cc: Yoder, Jess; Salgaonkar, Jag; Herberg, Jim; Smith, Matt
Subject: OCSD Secondary Treatment Peer Review

-Attached are responses to Dr. Drury?s comments regarding toxicity issues. These are all excellent insights that we will consider further as we move forward with the implementation of our secondary facilities at both Plants 1 and 2. Toxicity is an important issue for OCSD. We are currently conducting several studies (see comments below), and we are planning several more that will help define the nature of our specific toxicity concerns and develop plans to provide necessary treatment to mitigate it. As a result of Dr. Drury?s comments, we will insert a study that will help us define the proper treatment technology to employ at Plant 2; trickling filters or activated sludge, prior to the project design phase. We will assure that the implementation schedule has adequate time built into it to accommodate this study work and we will assure that the design and construction schedule will accommodate either technology. A revised schedule reflecting these changes will be made available for discussion at the meeting next Wednesday. We want to reemphasize that the focus of the Peer Review Panel should be on the implementation schedule and we would appreciate your insights into what we have proposed. Thank you for your continued help and we look forward to discussing these issues with you next week.

----Original Message-----
From: D4 [mailto:D4@ieua.org]
Sent: Friday, January 31, 2003 9:23 AM
To: Ludwin, David
Subject: OCSD Peer Review

Dave, Here are my comments from our first meeting. Would you make sure that the others on the committee receive a copy?

1. Your operations plan assumes that dilution will take care of the chronic toxicity. It also assumes that acute toxicity will not be in the future permit. From what little I know about EPA, they will allow a zone of initial dilution for chronic but not for acute toxicity. Therefore, the assumption that dilution will take care of the toxicity may not be a good one. Your team did not appear to be knowledgeable in the toxicity requirements when questioned. If the designers are not aware of the potential problem or assume it will go away, then the project will probably not address the issue. 2. Your staff has assumed that ammonia or water hardness toxicity are the only toxic sources. I would not make that assumption. My experience has been that there are multiple sources of toxicity. Ammonia and hardness may be obscuring the impact of other toxicants.

We are anticipating toxicity permit conditions that are consistent with the California Ocean Plan. Under the California Ocean Plan, chronic toxicity testing allows dilution with sea water. The rationale is that salt water test species need to have some saltwater to survive. Salt water dilution will also be allowed for the acute test.

Studies presently underway will define the degree that ammonia and hardness govern our toxicity. Other toxicants certainly can contribute to toxicity, and their impact is probably magnified if the test organisms are stressed by high ammonia and hardness. Our testing will confirm whether the Ocean Plan toxicity testing requirements can be satisfied if our ammonia levels are brought down. We are considering ammonia not as the only toxicant, but as the single constituent with the largest impact, and the one that is easiest to reduce.

Recognizing that we will need flexibility in our future operation to meet toxicity requirements, we are planning to size our air activated sludge facilities for Nitrification.

3. The operations plan states that you don't want to address the toxicity issue because it is too complicated and will confuse the TIE results. We have performed two formal TIEs. Neither study identified the specific toxicant. I would not wait to address the problem. If you believe that ammonia is a source of toxicity, then I would fully nitrify your effluent and eliminate the toxic source. Only then will you be able to address the potential toxicity from other sources.

There are two ongoing studies addressing toxicity and ammonia management. The first study is a series of bioassay tests being conducted by the OCSD Environmental Compliance and Monitoring Group. The testing is designed to simulate our future operation with the GWR System on-line, including RO concentrate blending into the final effluent. The test will be run with varying ammonia and hardness concentrations to identify a range of values that will give a satisfactory toxicity level.

The second study, Job No. P1-80 is developing design criteria and is comparing alternative treatment strategies to meet the ammonia levels identified in the bioassay testing. Options include nitrified activated sludge, nitrification of the belt press wash water, and nitrification of the RO concentrate. The optimal combination of these three options necessary to satisfy the toxicity level as defined in the bioassay work will be identified.

4. OCSD plans on doing two things that could increase the toxicity that other plants are not doing. First, you plan on treating a large amount of dry weather urban runoff. Secondly, you plan on treating the reject water from the RO units of the GWRS project. The urban runoff will bring residential herbicides and pesticides. The RO reject water will bring with it concentrated trace organic chemicals such as endocrine disrupters and pharmaceuticals. Direct experience of others in treating these chemicals is very limited. We have successfully used a high MLSS, high SRT activated sludge process to treat and remove pesticides such as; diazinon, chlorpyrifos and lindane, as well as other organics such as NDMA. I believe that you need a plan to treat these and other toxic chemicals that may enter your plant.

So far we have seen no increase in our effluent toxicity since we began accepting urban runoff diversions. If unacceptable levels of pesticides or other toxicants were to be present in the urban runoff, OCSD?s Source Control Division would take action to stop the diversions to the treatment plants.

The RO reject water will be blended into our ocean discharge and will not be blended into any source water for reclamation. Any trace contaminants in the RO reject water would have been in our effluent anyway if no reclamation was done. As mentioned above, bioassay tests are being run to determine the impact of increased concentrations on toxicity. We are also designing our air AS facilities with the capability to operate with high MLSS and SRT to reduce toxicity if needed.

5. You have selected the trickling filter process for producing secondary effluent for ocean discharge. If you were not treating urban runoff and RO reject water, trickling filters would be a good decision. But you are treating unique flows and you are going to produce waters for recharge of the drinking water aquifer. A high MLSS, high SRT activated sludge process will produce a better quality water than trickling filters. If I were in your position, I would not use trickling filters alone to treat potential drinking water, urban runoff, or RO reject water.

OCSD agrees that additional studies are needed before we finalize the selection of secondary treatment processes for Plant No. 2. Based on the results of the Job No. P1-80 study, the RO reject water will either be blended directly with our effluent or treated in a separate high MLSS, high SRT biological process. The above-mentioned toxicity studies will simulate OCSD?s effluent quality with the GWRS RO concentrate blended in, and will help confirm the level of nitrification that is necessary to meet our toxicity limits. Preliminary ammonia balance calculations indicate that nitrification at Plant No. 1, combined with sidestream ammonia removal will reduce effluent ammonia levels to below 25 mg/L, a level at which OCSD has consistently passed toxicity tests. Further studies will be needed to finalize the secondary treatment design criteria.

The issue of organic contaminants is being addressed by the GWR System in a number of ways as listed below.

• The Orange County Water District, in partnership with OCSD has been studying projected GWR System product water quality and has prepared a report titled Groundwater Replenishment System Water Quality Evaluation, by Eisenberg, Olivieri and Associates, using a blue ribbon panel. The projected product quality from the GWR System will meet all State DOHS requirements and the California Regional Water Quality Control Board as defined in the Groundwater Replenishment System Title 22 Engineering Report
• OCSD has committed to an enhanced source control program to prevent contaminants of concern such as endrocrine disrupters from entering the sewers tributary to Plant No. 1 and the GWR System.
• Phase 1 of the GWR System will require 104 mgd of secondary effluent with a maximum turbidity level of 5 NTU. This NTU limit will require that most of the effluent sent to the GWR System be activated sludge (AS), with some trickling filter (TF) effluent.
• In addition to the existing 80 mgd of AS treatment and 30 mgd of trickling filter treatment, an additional 70 to 80 mgd of air activated sludge is planned for Plant No.1 as part of the full secondary expansion. These AS facilities will be designed to provide high MLSS and SRT for nitrification, if needed, to control effluent ammonia concentrations. Once the full secondary facilities are constructed, there will be more than enough AS capacity to provide 104 mgd of AS effluent to the GWR System.
• The GWR System is being designed around our historical and projected secondary effluent quality and the Title 22 requirements for reuse including total organic carbon, NDMA, total nitrogen, total dissolved solids, turbidity, total coliforms, BOD, and TSS.
• OCWD is performing endocrine disruptor studies to determine the removal of estrogen and selected pharmaceuticals by the MF/RO/UV-H2O2 treatment process. The testing is complete and the results are being analyzed. A report should be coming soon.
• The RO process will provide demineralization and will remove organics, nitrogen-nitrosodimethylamine (NDMA), and microbial pathogens. UV light will be used for disinfection and destruction of NDMA. The combined use of RO and UV treatment is consistent with the multiple barrier approach to disinfection used at drinking water and water reuse plants.
• Water quality data from the Demonstration Project indicates that GWR System water will meet all the requirements of the Primary and Secondary California Drinking Water Standards. With regard to key constituents, the Total Organic Carbon (TOC) of the recycled water is projected to be about 0.26 milligrams per liter (mg/L) because the entire flow stream will receive full RO treatment. The combination of RO and UV treatment is designed to reduce the concentration of NDMA to below the action level.

6. You should consider treating separately the filtrate flows from belt press dewatering (not belt wash) and the RO reject water (not micro filter wash water). The belt wash and the micro filtration wash water probably should be returned to primary clarification. You may be able to treat both the filtrate and RO reject water in the same separate activated sludge process. The effluent from this activated sludge process should probably go to the main flow activated sludge process. You could use the WAS from the main flow activated sludge to continually seed the process and not use any RAS.

The Belt Press Filtrate Treatment study, (Job No. P1-80) will identify the treatment necessary for the belt press wash water and RO reject water. A combined AS process for the belt press filtrate and RO concentrate is one of the alternatives being studied under P1-80. Using WAS from our AS plant to feed the side stream treatment should be looked at in the study as suggested.

We are planning to return the MF backwash to the primary clarifiers as suggested. OCSD?s operations engineers are doing jar tests now to determine if primary clarification is effective in removing SS form the MF back wash. If primary clarification isn?t effective, we may decide to send the MF backwash directly to secondary treatment plant.

7. You may want to consider trying to convert the Plant 2 pure oxygen system to a high MLSS, high SRT nitrifying process. This would require some creative engineering and operation. You could use the first oxygen reactor as an anoxic selector, the second and third for oxygen transfer, and the fourth could be open to the atmosphere to strip out residual O2 and CO2. I believe that this would enhance the removal of pesticides and herbicides from urban runoff.

The bioassay studies currently underway by Jeff Armstrong will be used to estimate treatment requirements necessary to control toxicity in the future. We are presently meeting our toxicity limits with 65% secondary treatment an ammonia concentrations averaging 29 mg/L. and will be moving to full secondary treatment. Thus far, the need to provide 100% high MLSS, high SRT nitrifying AS effluent for our ocean discharge has not been demonstrated. If we experienced increased toxicity from pesticides in urban runoff diversions, we might consider discontinuing the diversions or separate treatment of the urban runoff. As stated above, more studies are needed to decide on the final secondary treatment configuration.

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