Appendix C1 SBR/MBR Wastewater Facilities Analysis

Wastewater Treatment System for Title 22 Reclamation at the Malibu Civic Center Area 1.

DESIGN CRITERIA

The proposed wastewater treatment facility in the Civic Center Area of Malibu will provide treatment of residential and commercial domestic wastewater for reclamation as unrestricted use irrigation water. Thus the treatment system will have to treat the wastewater to levels that meet Title 22 requirements for reclaimed wastewater as well as meet effluent limits required by the Regional Water Quality Control Board (RWQCB). The design criteria for the treatment plant include the estimated influent water quality, the Title 22 and RWQCB effluent requirements, and the influent flow rate. There are two possible influent flow rates based on the selected collection system area and disposal option as discussed above. The influent and effluent water quality is the same for both flow options. The treatment system design criteria are as follows. The influent wastewater quality is expected to have a biochemical oxygen demand (BOD) of 300 mg/L, a total suspended solids (TSS) of 300 mg/L, and ammonia of 45 mg/L. The effluent limits are expected to be as follows: BOD TSS Total Nitrogen Turbidity

10 mg/L 10 mg/L 10 mg/L average of < 2 NTU < 5 NTU 95 percent of the time Never greater than 10 NTU CT (if using chlorine for disinfection) 450 min-mg/L with a minimum of 90 minute contact time Coliform < 2.2 MPN/100 mL The flow rate for Option 1 is an average dry weather flow (ADWF) of 120,000 gallons per day (gpd) with a peak wet weather flow (PWWF) of 150,000 gpd. The flow and loadings for Option 1 are presented in Table 1. Table 1 Wastewater Flows and Loadings Used for Option 1 Flow into New Treatment Plant ADWF, MGD PWWF, MGD BOD5 Concentration at ADWF, mg/L Loadings at ADWF, lb/day Loading at PWWF, lb/day TSS Concentration at ADWF, mg/L Loadings at ADWF, lb/day

0.120 0.150 300 300 375 300 300

Loading at PWWF, lb/day 375 Nitrogen ADWF Total Nitrogen, mg/L 45 Nitrogen loading at ADWF, lb/day 45 Nitrogen loading at peak month, lb/daya 60 ______________________________________________________________________________ a Loadings for Nitrogen increased by 1.3 for peak monthly conditions. The flow rate for Option 2 is an average dry weather flow of 200,000 gallons per day (gpd) with a maximum flow of 250,000 gpd. The flow and loadings for Option 2 are presented in Table 2. Table 2 Wastewater Flows and Loadings for Option 2 Flow into New Treatment Plant ADWF, MGD 0.200 PWWF, MGD 0.250 BOD5 Concentration at ADWF, mg/L 300 Loadings at ADWF, lb/day 500 Loading at PWWF, lb/day 625 TSS Concentration at ADWF, mg/L 300 Loadings at ADWF, lb/day 500 Loading at PWWF, lb/day 625 Nitrogen ADWF Total Nitrogen, mg/L 45 Nitrogen loading at ADWF, lb/day 75 Nitrogen loading at peak month, lb/daya 100 ______________________________________________________________________________ a Loadings for Nitrogen increased by 1.3 for peak monthly conditions. 2.

TREATMENT TECHNOLOGIES

As determined in the Preliminary Conceptual Plan for Wastewater Reclamation in the Civic Center Area dated July 7, 2003, the two treatment options considered for this feasibility study are a sequencing batch reactor (SBR) and a membrane biological reactor (MBR). Both systems have a history of meeting the discharge requirements at various locations. A description of each follows. 1.

PROCESS DESCRIPTION

An SBR is a fill-and-draw reactor system that utilizes a single complete mix reactor in which all the steps of the activated sludge process occur. The fill-and-draw mode of operations utilizes four cycles: fill, react, settle, and decant. The activated sludge mixed liquor remains in the reactor during all cycles, thereby eliminating the need for a separate secondary sedimentation

tank. To provide for nitrogen removal an anoxic sub-cycle is added during the react cycle for denitrification. The SBR system will provide an effluent suspended solids in the 15 to 20 mg/L range. However, to reliably meet the anticipated, stringent effluent total coliform limit of 2.2 MPN/100 mL, a very low turbidity effluent is required. In addition, a low suspended solids effluent should improve land disposal capacity and extend the life of the disposal system. Therefore, filtration is required to provide suspended solids at a range of 5 to 10 mg/L. To provide for equalization of peak flows and emergency storage, an influent equalization tank was included in the SBR system considered for this project. An SBR treatment system will consist of influent flow metering, screening, the SBR system, filtration, disinfection, effluent flow metering, an aerated sludge tank, and sludge dewatering. The principal manufacturers of SBR systems are Fluidyne, Cass, and Aqua Aerobics. An MBR is an activated sludge reactor system that utilizes a single complete mix reactor in which all the steps of the activated sludge process occur with a membrane filter system submerged in the reactor. The membrane filter system filters the water continuously from the reactor by the suction from a pump. As with the SBR, the activated sludge mixed liquor remains in the reactor during all cycles, thereby eliminating the need for a separate secondary sedimentation tank. In addition, the filtration system is located within the reactor, thereby eliminating the extra space required for a filter system. To provide for nitrogen removal an anoxic stage is added for denitrification. MBR systems are continuous gravity flow-through systems and are sized for the average flow. If the peak flow conditions are greater than two times the average flow at any time, then an equalization tank must be installed prior to the biological treatment tank to provide flow equalization. For comparison purposes, the same influent equalization tank was provided for both the MBR and SBR. An MBR treatment system will consist of influent flow metering, screening, the MBR system, disinfection, effluent flow metering, an aerated sludge tank, and sludge dewatering. The principal manufacturers of MBR systems are Zenon, Kubota, Mitsubishi, and Ionics. 2.

FACILITY REQUIREMENTS

The facilities required for the SBR and MBR systems are provided below. The MBR system includes membrane filtration in its design. The SBR system requires a filtration system. A description of the filtration system options follows the discussion of the SBR facilities. Both the SBR and the MBR require influent and effluent flow metering, screening, disinfection, and sludge aeration and dewatering. A description of these facilities is provided after the following discussion of the filtration systems. MBR The facilities required for the MBR system are a concrete rectangular tank divided into three cells (influent equalization, anoxic zone, and aerated/filtration zone), pumps, electrically actuated valves, blowers, level controls, a programmable logic controller (PLC), and ultrafiltration membrane filter. The screened raw wastewater is discharged to the anoxic cell. The raw wastewater is mixed with recirculated mixed liquor in the anoxic cell and then flows to the aeration cell. In the aeration cell, the wastewater is aerated through a grid of fine bubble diffusers connected to positive displacement blowers. The ultra-filtration membranes are

immersed directly in the aerated mixed liquor and are either gravity fed or connected to the suction side of a centrifugal pump. The wastewater is biologically treated in the anoxic/aerobic bioreactor and the clean permeate is drawn through the membranes and discharged to the disinfection system. The MBR system will provide an effluent suspended solids in the less than 5 mg/L range and turbidity of