OPERATIONS and
MAINTENANCE PLAN
Mendenhall WWTP, Juneau AK
Prepared for: The City & Borough Juneau Alaska
LAST UPDATE:
January 2015
Operations and Maintenance Plan
TABLE OF CONTENTS
A. INTRODUCTION ... 3
A.1MENDENHALL WWTP NPDES PERMIT LIMITS ... 4
B. FACILITY DESCRIPTION... 6
B.1OVERALL PLANT ... 6
B.2LIQUID TRAIN ... 7
B.2.1PRE-TREATMENT ... 7
B.2.2 SEQUENCING BATCH REACTOR (SBR) BIOLOGICAL TREATMENT PROCESS ... 8
B.2.3 ULTRAVIOLET (UV) DISINFECTION ...15
B.2.4 NON-POTABLE WATER SYSTEM...15
B.3 SOLIDS PROCESSING ...15
B.3.1 WASTE AND THICKEN SLUDGE TANK ...15
B.3.2 DEWATERING ...16
B.3.3 OPERATIONAL PARAMETERS ...17
B.3.4 PERFORMANCE PARAMETERS ...17
B.3.5 POLYMER USE ...18
B.3.6 MONITORING, CONTROL AND RESPONSIBILITIES ...19
B.4 BEST MANAGEMENT PLANS AND SOPS ...19
C. PROCESS CONTROL STRATEGY ...19
C.1 CONTROL PARAMETERS ...20
D. SAMPLING PLAN ...20
D.1 SAMPLING PROGRAM DESIGN ...21
D.1.1 NPDES PERMIT MONITORING LOCATIONS, PARAMETERS MEASURED, AND COLLECTION FREQUENCIES ...21
D.2 SAMPLING METHOD REQUIREMENTS ...21
D.2.1 SAMPLE TYPES ...21
D.2.2 SAMPLE EQUIPMENT AND CONTAINERS ...22
D.2.3 SAMPLE PRESERVATION REQUIREMENTS ...23
D.2.4 CROSS-CONTAMINATION REDUCTION EFFORTS ...23
D.3 SAMPLE HANDLING AND CUSTODY REQUIREMENTS ...23
D.3.1 FIELD GRAB SAMPLE HANDLING ...23
D.3.2 CONTRACTED LABORATORY SAMPLE HANDLING ...23
D.4 SPECIAL TRAINING REQUIREMENTS/CERTIFICATION ...24
D.4.1 SAMPLE COLLECTION TRAINING ...24
D.4.2 METHODS TRAINING ...24
E. WEEKLY PROCESS CONTROL MEETING ...25
A.
INTRODUCTION
This Operations Plan is prepared to assist the plant staff in Juneau, AK to properly monitor and operate the wastewater treatment plant to consistently meet the objective of compliance. This operations plan is not intended to be all inclusive. Operations and maintenance staff members should review and fully understand state regulations, and the design and operations and maintenance manuals provided by the equipment suppliers for the plant.
An overview of the facility, including process components and general operational approach is discussed in the next sections. Detailed process monitoring and target set points are shown later in the Operations Strategy. More detailed discussion of each process is provided in the Unit Process Control Procedures (UPCP) and Standard Operating Procedures (SOPs) for each major process employed in the facility. Please refer to these documents for operational rationale, troubleshooting, and start up and shut down impacts and procedures.
This Plan also contains a sampling plan for the facility. While there is some latitude on collecting and analyzing process samples, the permit samples noted in the plan MUST be collected on the time and date specified, unless unusual circumstances prevent their collection at the appointed time.
The overall objective of the facility operation is to insure continuous compliance with the permit limits shown in the Exhibit Below.
A.1 MENDENHALL WWTP NPDES PERMIT LIMITS
TABLE 1 - Data Quality Goals for MWWTP Permit Parameters
Parameter Units Minimum Effluent Limits Monitoring Requirements
Daily Monthly Average Average Weekly Maximum Daily Location Sample Frequency Sample Sample Type
Flow MGD --- report --- 4.9 effluent continuous recording Dissolved Oxygen mg/L report --- --- report effluent 1/month grab Temperature °C --- report --- report effluent 1/month grab
BOD5
mg/L --- 30 45 60 effluent 2/month 24-hr composite lb/day --- 1226 1829 2452
mg/L --- report --- --- influent 2/month 24-hr composite % removal 85 See Permit AK0022951 Part 1.4.5 effluent vs influent 1/month calculation
TSS
mg/L --- 30 45 60 effluent 2/month 24-hr composite lb/day --- 1226 1829 2452
mg/L --- report --- --- influent 2/month 24-hr composite % removal 85 See Permit AK0022951 Part 1.4.5 effluent vs influent 1/month calculation pH (Nov 1 - Jun 30) s.u. 6.5 --- --- 8.5 effluent 5/week grab
(Jul 1 - Oct 31) s.u. 6.3 --- --- 8.5 effluent 5/week grab Fecal Coliform Bacteria
(Nov 1- Apr 30) FC/100 mL a --- 112 b 168 b 224 c effluent 2/week grab (May 1- Oct 31) FC/100 mL a --- 200 b 400 b 800 c effluent 1/week grab Total Ammonia as N
(Nov 1 - Apr 30)
mg/L --- 28.5 --- 40.5 effluent 1/month 24-hr composite lb/day --- 1165 --- 1655 calculation (Jun 1 - Oct 31) mg/L --- report --- report effluent 1/month 24-hr composite Copper d (Nov 1 - Apr 30) lb/day µg/L --- --- 3.54 86.7 --- --- 187.0 7.63 effluent 1/month 24-hr composite calculation (May 1 - Oct 31) lb/day µg/L --- --- 44.5 1.82 --- --- 95.8 3.92 effluent 1/month 24-hr composite calculation Lead d µg/L --- report --- report effluent 3/year e 24-hr composite Silver d µg/L --- report --- report effluent 3/year e 24-hr composite Zinc d µg/L --- report --- report effluent 3/year e 24-hr composite Whole Effluent Toxicity
(Nov 1 - Apr 30) TUc --- 5.1 --- report effluent 1/year 24-hr composite
(May 1 - Oct 31) TUc --- report --- report effluent 1/year 24-hr composite
Hardness mg/L as CaCO3 --- report --- report effluent 1/month 24-hr composite
Alkalinity mg/L as CaCO3 --- report --- report effluent 1/quarter f 24-hr composite
Floating Solids/Visible Foam visual --- See Permit AK0022951 Part 1.2.4 effluent 1/month visual
Notes:
a. FC/100 mL = colonies of fecal coliform bacteria (FC) per 100 mL.
b. All fecal coliform bacteria average results must be reported as the geometric mean. c. Not more than 10 percent of samples may exceed the daily maximum limit.
d. Metals monitoring in the effluent must be analyzed for and reported as total recoverable metal.
e. Lead, silver and zinc must be sampled at least once during each of the following periods each year: January through April, May through August, and September through December. Results must be submitted with the April, August, and December DMRs.
Quarters are defined as January - March, April - June, July - September, and October - December. Results must be submitted with the DMR for the last month of the quarter
TABLE 1a - MWWTP Effluent Discharged Receiving Waters Monitoring Requirements
Parameter Units Sampling Location Frequency Sampling Sample Type Reporting Limit
Temperature oC upstream and downstream 1/month grab ---
Fecal coliform a FC/100 mL upstream and downstream 1/month grab 1.0 Total Ammonia as N mg/L upstream and downstream 4/year b grab 0.05 pH s.u. upstream and downstream 1/month grab ---
Copper c µg/L upstream and downstream 2/year d grab 2.0 Lead c µg/L upstream 2/year d grab 2.0 Hardness mg/L as CaCO3 upstream and downstream 1/month grab 10
Dissolved oxygen mg/L upstream and downstream 1/month grab --- Alkalinity mg/L as CaCO3 upstream 1/month grab 10
Notes:
a. All mixing zone fecal coliform bacteria average results must be reported as geometric means.
b. Sampling must occur at least twice during each of the following time periods: November through April; and May through October.
c. Analysis values for copper and lead must be as dissolved metal.
d. Sampling must occur at least once during each of the following: May 1 through October 31; and November 1 through April 30.
TABLE 1b - MWWTP Additional Effluent Monitoring for Permit Reissuance
Parameter Units Sample Location Sample Frequency Sample Type
Total Ammonia as N mg/L effluent 3x/4.5 years 24-hr composite Dissolved Oxygen mg/L effluent 3x/4.5 years grab Nitrate Plus Nitrite Nitrogen mg/L effluent 3x/4.5 years 24-hr composite Total Kjeldahl Nitrogen mg/L effluent 3x/4.5 years 24-hr composite Oil and Grease mg/L effluent 3x/4.5 years grab Total Phosphorous mg/L effluent 3x/4.5 years 24-hr composite Total Dissolved Solids mg/L effluent 3x/4.5 years 24-hr composite Expanded Effluent Testing varies effluent 3x/4.5 years ---
Notes:
e. Metals monitoring in the receiving water samples must be analyzed for and reported as dissolved metal.
f. Sampling must occur at least once during each of the following: November - May, June, July - September, and October. g. Sampling must occur at least once during each of the following: November - May and October - June.
h. Sampling required during May, June, July, August, September, and October only.
B.
FACILITY DESCRIPTION
This section discusses the basic purpose of each process in the plant and what processes units/equipment that are provided for each. Operating parameters are shown in the Process Control Strategy that follows and in more detail in the UPCPs and SOPs.
Figure 1 – Process Flow
B.1 OVERALL PLANT
The Mendenhall Wastewater Treatment Plant (MWWTP) is a 4.9 MG Daily Max activated sludge facility utilizing SBR (Sequential Batch Reactors) technology. Wastewater enters the facility by gravity and debris is removed in the headworks. As it enters the plant it first flows through a grinder and then in a channel auger screen. The raw water then enters the IPS (Influent Pump Station). A combination of five pumps will then pump the raw water to the splitter box in the grit removal system, from there it flows to the SBR tanks that are in “Fill Mode”. Mixed liquor leaves the SBRs during the “Wasting Mode” and is pumped either to the waste sludge or thickened sludge tank. Normal operating conditions only require that seven SBRs be operated due to the hydraulic ratios loading on the facility.
Table 2 Mendenhall WWTP Design Parameters
Parameter
Units
Daily Avg.
Metric
Flow MGD 2.70 10,220 mˆ3/d MGD/ Peak 6.75 25,549 mˆ3/d BOD, Influent mg/L 260 2,655 kg/d Lbs./d 5,855 TSS, Influent mg/L 220 2,247 kg/d Lbs./d 4,954 Ammonia, Influent mg/L 30 306 kg/d Lbs./d 676 TKN, Influent mg/L 45 460 kg/d Lbs./d 1013 SBR basin MLSS mg/L 2,200
F/M (unadjusted for aer.
Time) 0.15
When the loading on the plant is within the design parameters below, it is capable of meeting the National Pollutant Discharge Elimination System (NPDES) Permit limits listed above.
B.2 LIQUID TRAIN B.2.1 PRE-TREATMENT
Wastewater enters the IPS through a pair of 30”gate valves into individual channels. It then gravity flows through the main channel into a JWC Auger Monster where debris is shredded, washed and screened. The influent flow may be bypassed through the secondary channel, which employs a manual bar rack, to allow for maintenance to the Auger Monster without interruption of influent flow to the wet well.
Immediately following screening, wastewater flows by gravity into the IPS. The pump station is equipped with five submersible pumps, each of which is capable of 2100 GPM (at 64 ft. TDH). The pumps are controlled automatically to activate/ deactivate as the liquid level in the wet well rises/falls. This type of operation allows the pump station to accommodate the wide variations in influent flow rates. During normal operation, the influent pumps operate in Automatic mode. In Manual Mode, the operating sequence of the pumps can be selected by the operator. Fluid from the wet well is pumped to the grit chamber head box at approximate elevation 52.0 Ft to a splitter box where it goes through three centrifugal grit separator vessels (Tea Cups) and concentrated into a slurry. The concentrate then drops down to the main floor level where it enters a clarifier and conveyor (Grit Snail) where it is dewatered and conveyed into a hopper for landfill disposal.
The influent flow is monitored through two flow meters. IPS pumps 1, 2 & 3 have flow measured by FE-01 with pumps 4 & 5 measured by FE-02.
Table 2a
Process Unit Quantity Description Location
Grinder/screener Grit separation Grit dewatering Influent Pumps 1 1 1 5 JWC Auger Monster TM Eutek Tea Cup®
Eutek Grit Snail ®
ABS, Pumps
Influent Pump Station Influent Pump Station Influent Pump Station Influent Pump Station
B.2.2 SEQUENCING BATCH REACTOR (SBR) BIOLOGICAL TREATMENT PROCESS
The MWWTP is an eight tank SBR Activated Sludge Wastewater Treatment Plant that operates with one tank serving as flow equalization or emergency storage tank. Each basin has its own dedicated positive displacement blower, jet pump, waste pump, level sensors, influent and mud valve, and jet header mixing/aeration system.
Operation of the SBR plant is based on a fill-and-draw principle, which consists of five steps; fill, react, settle, decant, and idle. These steps can be altered for different operational applications.
Fill – During the fill cycle, the basin receives influent wastewater. The influent flow brings food to the microbes in the activated sludge, creating an environment for biochemical reactions to take place. Mixing and aeration can be varied during the fill cycle to create the following three different scenarios:
Static Fill – Under a static-fill scenario, there is no mixing or aeration while the influent wastewater
is entering the tank. Static fill can be used when there is no need to nitrify or denitrify, and during low flow periods to save power. Because the jet pumps and aerators remain off, this scenario has an energy-saving component.
Mixed Fill – Under a mixed-fill scenario, the jet pumps are active, but the blowers remain off. The mixing action produces a uniform blend of influent wastewater and biomass. Because there is no aeration, an anoxic condition is present, which promotes denitrification. Anaerobic conditions can also be achieved during the mixed-fill cycle. Under anaerobic conditions the biomass undergoes a release of phosphorous. This release is reabsorbed by the biomass once aerobic conditions are reestablished. This phosphorous release will not happen with anoxic conditions.
Aerated Fill – Under an aerated-fill scenario, both the aerators and the jet pump are activated. The contents of the basin are aerated to convert the anoxic or anaerobic zone over to an aerobic zone. No adjustments to the aerated-fill cycle are needed to reduce organics and achieve nitrification. However, to achieve denitrification, it is necessary to switch the oxygen off to promote anoxic conditions for denitrification. By switching the oxygen on and off during this cycle with the blowers, anoxic conditions are created, allowing for nitrification and denitrification. Dissolved oxygen (DO)
should be monitored during this cycle so it does not go over 0.2 mg/L. This ensures that an anoxic condition will occur during the idle cycle.
React
This cycle allows for further reduction or "polishing" of wastewater parameters. During this cycle, no wastewater enters the basin and the mechanical mixing and aeration units are on. Because there are no additional volume and organic loadings, the rate of organic removal increases dramatically. Most of the carbonaceous biochemical oxygen demand (BOD) removal occurs in the react cycle. Further nitrification occurs by allowing the mixing and aeration to continue—the majority of denitrification takes place in the mixed-fill cycle. The phosphorus released during mixed fill, plus some additional phosphorus, is taken up during the react cycle.
Settle
During this cycle, activated sludge is allowed to settle under quiescent conditions—no flow enters the basin and no aeration or mixing takes place. The activated sludge tends to settle as a flocculent mass, forming a distinctive interface with the clear supernatant. The sludge mass is called the sludge blanket. This cycle is a critical part of the treatment process because if the solids do not settle rapidly, some sludge can be drawn off during the subsequent decant cycle and thereby degrade effluent quality.
Decant
During this cycle, a decanter is used to remove the clear supernatant effluent. Once the settle cycle is complete, a signal is sent to the decanter actuator to initiate the opening of an effluent-discharge valve. The floating decanter maintains the inlet orifice slightly below the water surface to minimize the removal of solids in the effluent removed during the decant cycle. It is optimal that the decanted volume is the same as the volume that enters the basin during the fill cycle. It is also important that no surface foam or scum is decanted. The vertical distance from the decanter to the bottom of the tank should be maximized to avoid disturbing the settled biomass.
Wasting/Idle
This step occurs between the decant and the fill cycles. The time varies, based on the influent flow rate and the operating strategy. During this cycle, a small amount of activated sludge at the bottom of the SBR basin is pumped out—a process called wasting.
Sludge wasting should occur during the idle cycle to provide the highest concentration of mixed liquor suspended solids (MLSS). The plant should be operated on pounds of MLSS and not concentration.
Sludge from the SBR basins is wasted to a holding tank for future processing and disposal. The sludge-holding-tank capacity is not sized for extended storage of the wasted sludge and should be processed daily to allow room for additional wasting.
Figure 2 – SBR Phases
Wasting Rates
Wasting rates are an essential control in every activated sludge plant. It affects sludge age, ratio of loading to biology, and biology characteristics. MWWTP’s design information indicates that at design loading, the intended F/M is 0.15, the design Solids Retention Time (SRT) would be 7.67 days, and the Mixed Liquor Suspended Solids (MLSS) will be 2,200mg/L. When not at full loading, we can run with a higher SRT to reduce “yield” and provide greater stabilization of solids.
To determine Waste Activated Sludge (WAS) rates we can use a modified version of SRT. To establish wasting we start with calculation of inventory. If we select say, a 10 day target SRT, we need to waste 1/10th of the inventory each day. The calculation looks like this:
Pounds per day to waste = (7cells)(0.311650 MG/cell)(average MLSS)(8.34) Desired SRT
Gallons per day to waste = (Pounds per day to waste)(1000000) (WASSS)(8.34)
Minutes per cycle to waste = ___________Gallons per day to waste_____________ (number of SBR cycles per daily wasting period)(1200 gal/min)
Anoxic Time
MWWTP does not have strict limits on effluent nitrogen, thus anoxic time is not needed for denitrification. Brief anoxic conditions are useful however to exert a selector effect against filamentous organisms that interfere with settling. Most filaments are obligate aerobes and are out-competed by facultative floc forming bacteria in taking up BOD under unaerated conditions. Sufficient anoxic time usually occurs passively during the fill cycle. An operator should just be aware that if aeration times are set very high, it may encroach on the anoxic time during the fill cycle and reduce the selector effect.
Reaction/Aeration Times and DO Concentrations
In Flow Proportioned Mode, the control system adjusts the aeration time per cycle (between a minimum and a maximum that is set) to be proportional to the percent of plant capacity being used at the time (with the value entered as the “air slope set point” defining the aeration time at 100% of plant capacity).
However, the usual way of operation is Full Cell Mode. In this mode the same amount of wastewater is treated in each cycle, therefore, we want to deliver nearly the same amount of air each cycle. So, we set the minimum and maximum air settings close together. Assume actual air time will match the setting entered into the “minimum air set point.”
Now, how much air time is just right? Aeration in each cycle should be long enough that biology has an opportunity to take up the BOD that came in during the Fill Cycle. Operators can become familiar with the behavior of D.O. compared to the rate of application of air. View this behavior on the Supervisory Control and Data Acquisition (SCADA) screen.
Number of Cells in Operation
MWWTP SBR is an eight-cell reactor. The plant is designed to treat its capacity with seven cells in operation and the eighth left as a redundant (backup) unit. Operators have the option of using all eight cells during periods of high loading if desired, but operators should recognize that if a mechanical failure occurs requiring a cell to need to be emptied, the other seven cells would then need to accept the volume and the mixed liquor solids from the cell being dewatered as well as treating the forward flow through the plant. It could introduce additional stress to the plant at a time when it is already stressed. While standing by as a redundant unit, the eighth cell serves a function as an EQ vessel (as does any empty cell not in “auto”). It is available to accept influent when the incoming flow rate exceeds the ability of the other seven cells to receive it. The stored influent can then be feed into the plant at a later, less stressed time.
SBR Automated Control
Access to the control system is through a graphical computer interface Supervisory Control And Data Acquisition (SCADA) interface running on a dedicated pair of PCs. One PC functions as the principal control interface and the second, as a “hot backup” and ancillary terminal. This enables process adjustments and logging data/trends of levels and alarms. Operator adjustable process variables are accessible through the computer interface. The interface also enables access to logged information on DO levels, tank levels, alarms, hour meter readings, elapsed step times, pump and blower running status, etc. The levels in the reactors, IPS and sludge holding tanks are monitored by level sensors mounted in each tank. The control system provides accurate metering of the flow through the plant eliminating the need for a plant effluent flow meter.
The control system can be accessed from virtually anywhere in the world using a remote computer, software and electrical communication access. By this method the operator and support personnel can remotely adjust process variables, check plant status and operational trends. This is particularly useful for alarm 'call outs' so the operator can check the nature of the call and determine before leaving home, the type of response required. Also if the operator is away for a period of time, the operator can monitor plant status and adjust process settings from anywhere in the world. The data acquisition is particularly useful for troubleshooting the plant. The system also incorporates an auto-dialer for alarm conditions while the plant is unmanned.
The control system interacts with field devices and equipment through a programmable logic controller (PLC). A PLC consists of two basic sections: the central processing unit (CPU) and the input/output interface system. The CPU controls all PLC activity and the input/output system is physically connected to field devices (e.g., actuators, level sensors, pumps, blowers, etc.) and provides the interface between the CPU and the information providers (inputs) and controllable devices (outputs).
To operate, the CPU "reads" input data from connected field devices through the use of its input interfaces, and then performs the control program that is stored in its memory system. Programs are created in ladder logic, a language that closely resembles a wiring schematic, and are entered into the CPU's memory prior to operation. Finally, based on the program, the PLC updates output devices via the output interfaces. This process continues in the same sequence without interruption, and changes only when a change is made to the control program.
Table 2b SBR Process Troubleshooting Guide
Sequencing Batch Reactor Troubleshooting Chart
Problem or
Observation Condition Process Control Analysis
Possible Causes Control Action
Loss of solids from reactor due to a high blanket
Poor sludge settling velocity and compaction SSV, SVI, diluted SSV, microscopic examination, NH3 - N, COD, D.O., SOUR
•Glutting (old sludge) • Decrease MCRT. •Classic bulking (young
sludge) • Increase MCRT.
• Filamentous bulking • Identify conditions contributing to filamentous growth and correct. See comments in narrative below. • Slime bulking • Add nutrients.
• Foam Trapping • Optimize pretreatment removal of oil and grease. • Highly nitrified or oxidized
sludge • Increase anoxic cycle, reduce aerobic cycle. • Toxicity • Isolate or split flow, identify
source of toxic influent and eliminate, increase aeration cycle, increase MCRT. 12
Sequencing Batch Reactor Troubleshooting Chart
Problem or
Observation Condition Process Control Analysis
Possible Causes Control Action
Rapidly settling blanket leaving particulate. Difficulty in maintaining waste concentration
Rapid sludge settling velocity and compaction
SSV, SVI, F/M,
SOUR • Low F/M ratio • Increase F/M ratio by decreasing MLVSS.
Turbid or cloudy effluent, disinfection problems
A.High effluent BOD or TS MLSS, MLVSS, D.O., pH, temperature, Influent COD or TOC, Influent NH3 –N, D.O., SOUR • Low MLSS or MLVSS • Increase MLSS/MLVSS. • Low D.O., temperature or pH • Increase aeration cycle in fill
react, increase MLSS, add alkalinity.
• High organic loading • If long-term, increase MLSS/MLVSS and aeration cycle.
• High nitrogenous loading • If long-term, increase MLSS/MLVSS and aeration cycle.
• Toxicity • Isolate or split flow, identify source of toxic influent and eliminate, increase aeration cycle, increase MCRT. B. High effluent NH3 – N (Incomplete nitrification) Influent and process NH3 – N, influent and process alkalinity, pH, temperature, SOUR, D.O.
• Influent NH3-N overload • Increase aerobic cycle. • Low D.O. • Increase aerobic cycle. • Low temperature • Increase aerobic cycle. • Inadequate aerobic
retention time • Increase aerobic cycle. • Low pH or alkalinity • Add alkalinity. • Low MLVSS (nitrifiers) • Increase MLVSS.
• Toxicity • Isolate or split flow, identify source of toxic influent and eliminate, increase aeration cycle, increase MCRT.
High-effluent TSS Individual particle washout Effluent and recycle TSS or turbidity, F/M, microscopic exam, SOUR
• Pin floc – low F/M • Increase waste cycle, decrease MLSS. • Pin floc – denitrification • Increase waste cycle,
decease MLSS, increase anoxic cycle.
• Pin floc – solids recycle • Optimize solids handling. • Straggler floc – high F/M • Decrease waste cycle, 13
Sequencing Batch Reactor Troubleshooting Chart
Problem or
Observation Condition Process Control Analysis
Possible Causes Control Action
increase MLSS, increase aeration cycle.
• Straggler floc – filamentous • Identify filamentous organism (see filamentous control above).
• Straggler floc – hydraulic • See mechanical troubleshooting section. • Individual bacterial cells in
effluent • Decrease waste cycle, raise MLSS, increase aeration cycle, if toxicity, remove source of toxic influent.
High-effluent NO3 - N High effluent NO3 –
N NO3 – N, pH, TOC or COD • Lack of or inadequate anoxic conditions • Increase anoxic cycle (may require decreasing oxic cycle). • Lack of or inadequate
carbon source • Add carbon (methanol or acetic acid). • Low pH, temperature or
MCRT • Add alkalinity, increase MCRT.
Foam Excessive foam or
scum on surface of SBR, flow EQ tank or chlorine contact chamber Microbiological examination, NO3-N, C-N-P ratio, SRT, oils and grease, D.O.
• The presence of hydrophobic filamentous bacteria may lead to excessive scum and foam. See section I.5.
• The presence of hydrophobic filamentous bacteria may lead to excessive scum and foam. See section I.5.
• Denitrification can result in sludge and foam on surface of SBR.
• Denitrification can result in sludge and foam on surface of SBR.
• Foam may also indicate a possible nutrient deficiency. This type of foam may be due to bacteria producing a natural polymer when subjected to nutrient deficient conditions for an excessive period of time.
• Foam may also indicate a possible nutrient deficiency. This type of foam may be due to bacteria producing a natural polymer when subjected to nutrient deficient conditions for an excessive period of time.
• Both too low and too high an SRT can cause foam problems.
• Both too low and too high an SRT can cause foam problems. • Fats, oils grease and other
non-degraded surface active organics can cause foam problems.
• Fats, oils grease and other non-degraded surface active organics can cause foam problems.
• Excessive (D.O. > 4.0 mg/L)
may cause foaming. • Excessive (D.O. > 4.0 mg/L) may cause foaming. 14
B.2.3 ULTRAVIOLET (UV) DISINFECTION
MWWTP converted its chlorine and sulfur dioxide disinfection system because of changing regulations and public safety concerns. As a result, UV disinfection became the choice for wastewater disinfection due to some significant advantages over chlorine-based disinfection. Specifically, UV has been proven effective in various types of effluent, requires less maintenance, non-hazardous and is cost-effective.
The Mendenhall UV 3000 system consists of three banks of 24 modules each. Each module has eight lamps and sleeves. Staff should consult the UV SOP as it covers routine inspection and cleaning of UV lamps and sleeves in each bank. Typically we clean one bank each week, thus the lamp cleaning frequency is once every three weeks.
Microorganisms in the water are exposed to ultraviolet light when they pass by special lamps. The UV energy instantly destroys the genetic material (DNA) within bacteria, viruses and protozoa, eliminating their ability to reproduce and cause infection. Unable to multiply, the microorganisms die and no longer pose a health risk.
B.2.4 NON-POTABLE WATER SYSTEM
The Non-Potable Water (NPW) system is a side-stream system located in the disinfection building. NPW pumps collect chlorinated water out of the downstream end of the contact chambers, and pump it into a 2,500 gallon pneumatic storage tank located in the NPW supply room. An air compressor in the same room keeps the tank pressurized. A 6" diameter pipe carries NPW from the pneumatic tank to the SBR facility.
B.3 SOLIDS PROCESSING
B.3.1 WASTE AND THICKEN SLUDGE TANK
Below the blower room are two tanks. These tanks provide storage of waste sludge. During the wasting cycle the waste sludge pump will energize and pump WAS to the waste sludge tank.
Table 2c
Process Unit Quantity Description Location
Waste Sludge Tank 1 62x24x16 ft
Each 178,000 gallons
Under Blower Room Thickened Sludge Tank 1 62x24x16 ft
Each 178,000 gallons
Under Blower Room Recycle/Jet Mix Pumps 1 per tank Centrifugal, 1500 gpm
5 HP
Under Blower Room
Each tank has its own continuously operated jet aeration pump, with START/STOP controls located in the blower room. Waste sludge flow into the waste sludge basin is monitored by two Polysonics Model LCDT single head doppler ultrasonic flow meters (FE03and FE04). Thickened sludge flow going to the belt filter press is monitored by a 4" MAG Meter (PE08). These three meters transmit 4 to 20 mA signals to the PLC, and flow information is displayed on both the control panel and on
the IDT screens. Actual flows are presented on the control panel on analog gauges, while IDT screens provide digital readouts of actual and total flows.
Flow ranges for the three sludge flow meters are as follows:
FE03 (waste sludge) 0-1500 gpm FE04 (waste sludge) 0-1500 gpm FE08 (belt press sludge) 0- 200 gpm
B.3.2 DEWATERING
The belt filter press (BFP) receives sludge from the Thickened Sludge Tanks (TSTs). Polymer is added to help drain water from the sludge. Sludge is squeezed between two belts to produce a cake that is between 10 percent and 20 percent solids. It is in this manner that the sludge is dewatered. The dewatered sludge cake is transferred from the press to a hauling truck via a conveyer belt for offsite disposal.
The purpose of sludge dewatering is to capture the solids in the dry cake and minimize the return solids to the liquid treatment process, while removing as much as water from the sludge as possible. This reduces the total volume and cost of material to be disposed of by hauling.
The BFP is fed directly from the aerobic Thicken sludge tanks by a variable speed, progressive cavity filter press feed pump. The sludge is injected with a polymer in a venturi tube apparatus upstream of the BFP on the discharge side of the pump. The venturi tube facilitates sufficient mixing of the sludge and polymer. Polymer is used to flocculate the sludge in a step known as conditioning, where polymer pulls solids particles together releasing water that is then drained away. After polymer addition, sludge is deposited on the BFP.
Dewatering of sludge on the BFP consists of two phases. The first is free drainage. The conditioned sludge is spread onto the moving belt. Water drains through the belt, leaving the flocculated sludge. As the belt moves, plows suspended above the belt cause the sludge to turn over, which allows water on the top to move down to the belt and drain away. Nearly all of the free water should drain from the sludge by the end of the drainage zone.
The second is the use of pressure to remove water from the sludge, which occurs in the remainder of the BFP. After the sludge on the top belt has been thickened by gravity the sludge is sandwiched between the top and bottom belts. Pressure on the belts is increased as they travel through a series of rollers. The increased pressure and shear forces remove more water from the sludge until all that is left is a relatively dry cake. At the end of the press the belts separate and the dried sludge cake is deposited in a roll-off container. Once the belts drop the dewatered sludge onto the conveyer, both the upper and lower belts are washed with a high pressure water supply to clean any remaining sludge from the belts prior to the belt beginning the process again. A wash water booster pump installed in line with BFP provides adequate spray nozzle pressure for effective belt cleaning. Plant reuse water is used as wash water.
Filtered water from the press (filtrate) flows to the plant recycle pump station via 8-inch drain line. Table 2d
Process Unit Quantity Description Location
Belt Filter Press 1 1.0 meter Press Building Press Feed Pump 1 Progressive cavity, Seepex
pump with variable gpm, 7.5 HP Motor
Press Building
Polymer Feed System 1 Fluid Dynamics feed system. 1.0 HP High pressure injector 100 PSI
Press Building
Wash Water Pump 1 Unknown gpm, 15 HP Press Building B.3.3 OPERATIONAL PARAMETERS
There are a number of different parameters that will help the operator control the belt press operation. These parameters are listed in Table 2. Included with each parameter are the unit measurement, range of values, target value, and frequency of monitoring. Following the table is a brief explanation of each parameter, its importance, how and when it is used, and how it relates to other parameters.
It should be noted that when making adjustments to parameters the operator should keep in mind that it takes time for the system to respond. Changes should be made in increments and the process allowed to stabilize before additional actions are taken.
Table 2e Operation Parameters
Parameter Units Range Target Frequency
Sludge feed rate % VFD speed 35-60 45 4/shift Sludge feed conc. % 0.5-1.5 0.5-1.5 1/shift Sludge cake conc. % 10-20 15 1/shift Polymer conc. % by vol 0.1-0.5 varies each batch Polymer feed rate % 24-92 varies 4/shift Belt speed ft./min 3.0 - 18 varies 1/shift Belt tension psi TBD 350 psi 1/shift B.3.4 PERFORMANCE PARAMETERS
The performance parameters listed in Table 2f are used to analyze the efficiency of the dewatering operation and to help make decisions on how to improve that efficiency.
Table 2f Belt Filter Press Performance Parameters
Parameter Units Range Target Frequency
Sludge cake conc. % 10-20 >15 daily
Cake production DT/D TBD TBD daily
Solids capture % 90-100 95 daily
Solids loading rate lbs/hr < 500 Varies daily 17
Polymer use lb/DT 8 - 16 Varies daily Sludge Cake Concentration
This parameter is an average of the solids in cake samples collected over entire day. The cake concentration, along with the quantity of sludge processed and the percent capture, determine the volume of sludge to be hauled to the landfill. If a downward trend is detected the operator should evaluate the operation parameters and correct the problem in order to maintain the efficiency of the operation.
Cake Production
This is the quantity of sludge dewatered by the press in dry tons per day. Tracking this measurement will help the operator monitor the effectiveness of dewatering.
Solids Capture
Filtrate samples are collected from the press every two hours and measured for total solids. Solids capture is calculated by subtracting the filtrate concentration from the sludge feed concentration, and dividing the remainder by the feed concentration and expressing the result as a percentage. Solids capture % = ((feed lbs/hr – filtrate lbs/hr) * 100) / feed lbs/hr
Solids capture is important because solids in the filtrate return to secondary treatment and impact that process.
Solids Loading Rate
The operator calculates the press loading by use of the standard pounds formula (MGD * TSS * 8.34) and dividing by the run time.
Solids loading rate, lb/hr = (feed mg/L * feed MGD * 8.34 Lb/gal) / (24 hrs/day)
The loading rate is important so that the BFP is not overloaded and percent capture and percent cake deteriorate.
B.3.5 POLYMER USE
Polymer use is the quantity of concentrated polymer, in pounds, used to dewater a dry ton of sludge. Keeping track of polymer use is important since the cost of polymer is a major belt press operating expense. The following formulas are used to calculate the polymer usage.
B.3.6 MONITORING, CONTROL AND RESPONSIBILITIES Operation and Monitoring Tasks
At the beginning of each shift, the operator receives a verbal update from the Senior Operator, reviews the belt filter press data collection sheet, and reads the operations log to become familiar with any problems and conditions noted by the previous shift. The operator then monitors the system for sludge characteristics, polymer dosage, drainage conditions and appearance of the cake, and makes adjustments as needed.
After the press operation has been optimized, the operator collects samples of sludge feed, cake, and filtrate for solids measurement. The operator also notes the polymer feed, sludge feed settings, and the speed of the belt.
Control Tasks
In order to operate the BFP effectively, the operator will need to monitor and adjust certain operation parameters as described in this procedure. These parameters include sludge feed rate, feed sludge concentration, polymer concentration, polymer feed rate, belt speed and belt tension. Control of the equipment associated with BFP operation are generally located on the BFP control panels located next to the BFP’s in the Solids Handling Building.
Duties of the Operator
The operator is responsible for monitoring the operation and controlling the performance of the sludge dewatering process, documenting its status, and changes made to it. The operator also collects cake and filtrate samples.
B.4 BEST MANAGEMENT PLANS AND SOPS
The following Best Management Plans are developed in the form of Unit Process Control Procedures and SOPs and are included as attachments for MWWTP:
1. UPCP - Influent Screening 2. UPCP - Influent Grit Removal 3. UPCP - UV Disinfection 4. SOP - SBR
5. SOP - Solids Management Straight WAS SOP 6. SOP - Solids Management SOP
7. SOP - Belt Filter Press
8. SOP - MWWTP Effluent Flow Measurement
UPCPs and SOPs are reviewed and modified at least once each year. Additional documents are being developed as process and equipment adjustments are made.
C.
PROCESS CONTROL STRATEGY
C.1 CONTROL PARAMETERS
Process Control Strategy
Facility Name MWWTP Date/ Revision # 4 November 2014 Rev. No. Process
Overview
The Mendenhall Wastewater Treatment Plant is a 2.7 mgd activated sludge process utilizing SBR Technology. The plant has the following processes: Influent screening, influent pumping, and SBR Tanks with jet aeration system, UV disinfection. The sludge system consists of a waste sludge and thickened sludge tanks and belt press dewatering with final disposal in a landfill in Oregon.
Control Strategy Wastewater is passed thru the preliminary treatment and pumped to one of seven on line SBRs (SBR 8 is for Stand-by) Plant loading is highly seasonal and corresponds to the local tourist season. Sludge is wasted to maintain a constant solids inventory in the SBR system. Inventory is determined and changed based on SRT, and base line average MLSS concentrations. Waste sludge stored in the waste sludge tank and transferred to the thickened sludge tank if and when decant occurs. The sludge is then dewatered through a belt press and sent to a landfill in Oregan
Control Parameters
Process Parameter Units Design Minimum Maximum
Bar Screens Automatic screw 1
Bar Screens Manual clean 1 On demand
Activated Sludge DO mg/L >2.0 2.0 3.5
Activated Sludge MLSS mg/L 2200 2000 3000
Activated Sludge System Pounds Lbs 50,000 75,000
Activated Sludge SRT days 9 15
Activated Sludge F:M #/d / # .15 0.1 .18
Activated Sludge Temperature °C 10 28
Dewatering Press Feed Rate gpm
Dewatering Cake Solids % 15-18% 15 --
Dewatering Polymer Usage #/Ton dry
slg 16
Dewatering Percent Capture % 95 >99
Troubleshooting SEE UPCP FOR PROCESS
Alternate Modes of
Operation SEE UPCP FOR PROCESS
Reference Documents
D. SAMPLING PLAN
Proper sampling is required to determine the efficiency of the process, to meet company standards and to comply with State and Federal Law. The samples that are routinely collected at MWWTP are shown in the exhibit below. Samples are required by the NPDES Permit under which the facility operates. All sampling points are labeled to clearly identify where the sample is to be collected. The sampling points are shown on the attached sampling location drawing.
Refer to the QAPP for proper collection and storage of samples, chain of custody (COC) requirements and quality assurance/quality control requirements.
MWWTP Sampling Schedule is shown in Table 4a. A plant layout showing the sampling locations is shown in Table 4b.
D.1 SAMPLING PROGRAM DESIGN
Sample collection locations, required sampling parameters, and frequency of collection are specified in the MWWTP NPDES Permit AK0022951. Sample collection locations have been indicated on Figure 3, while sampling parameters and collection frequencies have been summarized in Tables 1a, 1b and 1c.
• Influent samples assess the chemical/physical characteristics of wastewater entering the MWWTP and are used to calculate the percent removal for BOD and TSS (as compared to the effluent sample results).
• Effluent samples assess the chemical/physical characteristics of the treated wastewater discharged from the plant.
Ambient receiving water samples are collected, around the mixing zone, to assess any potential water quality impacts generated by discharge of the treated effluent to the receiving water body. The MWWTP mixing zone extends 150 meters upstream and downstream from the discharge.
D.1.1 NPDES PERMIT MONITORING LOCATIONS, PARAMETERS MEASURED, AND COLLECTION FREQUENCIES
Monitoring locations established in the NPDES permit for MWWTP (AK0022951) are shown in Table 7 with a site description and site location rationale.
Table 4 - MWWTP Monitoring Locations, Site Descriptions and Site Selection Rationale Site Description Latitude Longitude Sampling Site Location Rationale
MWWTP
MWWTP Influent 58° 21’ 44” N 134° 35’ 47” W Beginning of the treatment process MWWTP Effluent 58° 21’ 44” N 134° 35’ 50” W End of the treatment process Mendenhall River Discharge 58° 21’ 43” N 134° 35’ 53” W ---
Mendenhall River Mixing Zone
Upstream Sample Site 58° 21’ 48” N 134° 35’ 49” W Upstream boundary used to monitor for any deterioration in receiving water quality due to the discharge of treated effluent Mendenhall River Mixing Zone
Downstream Sample Site 58° 21’ 39” N 134° 36’ 1” W Downstream boundary used to monitor for any deterioration in receiving water quality due to the discharge of treated effluent
Plant-specific sampling parameters and collection frequencies have been denoted in Tables 2a, 2b, and 2c for the MWWTP from NPDES Permit AK0022951.
D.2 SAMPLING METHOD REQUIREMENTS
This section describes the procedures that will be used to collect, preserve, transport, and store samples in compliance with NPDES requirements. Samplers should wear disposable gloves and safety eyewear, be aware of the potential hazards, and take care not to touch the inside of bottles or lids/caps during sampling.
D.2.1 SAMPLE TYPES
Water quality samples collected under the NPDES permit are either composite or grab, as shown in Tables 1, 1a, 1b. Composite samples are collected over a given timeframe directly into a refrigerated sample carboy. Small aliquots are taken from the sample stream and deposited directly
into the sample container; the volume of the aliquots can vary based upon system operations (i.e., flow-paced or standard volume). The sample container is held at 4°C + 2°C for sample preservation. The time of the first sample aliquot, composite intervals, and the final compositing time are noted in logbooks or on bench sheets. The final compositing time is the sample collection time noted on the COC form. Grab samples are collected in one collection bottle at a discrete time.
D.2.2 SAMPLE EQUIPMENT AND CONTAINERS
City and Borough of Juneau (CBJ) sample collection equipment and field instrumentation is detailed in Table 4a.
Table 4a - CBJ Sample Collection Equipment and Field Instrumentation
Vendor Model Description Site Location
Sigma 1600 24-hour composite sampler MWWTP Influent Sigma 900 24-hour composite sampler MWWTP Effluent
Hach 2100Q Turbidimeter MWWTP Hach SS6 Online Turbidimeter MWWTP H-B S/N 1246208 Thermometer MWWTP Thermo-Scientific Orion Star A212 Conductivity MWWTP Thermo-Scientific A3265 pH, temperature, and DO meter MWWTP
Samples are collected in either polyethylene or glass containers. Shown in Table 4b is a summary of sample containers, types of preservation, sample volume, and permissible hold times associated with sample collection. Sample containers are provided by the contracted laboratory. Fecal coliform samples are collected in sterile, disposable specimen containers.
Table 4b - Summary of Sample Containers, Preservation, Volumes, and Hold Times
Group Parameter Containera Preservation Holding Time Maximum Minimum Volume
General Water Quality
pH P, G None required < 15 min 100 mL Temperature P, G None required in-situ 100 mL
Dissolved Oxygen P, G None required < 15 min/in-situ 300 mL
TSS P, G 0 < 6 °C 7 days 1 L TDS P, G 0 < 6 °C 7 days 1 L BOD5 P, G 0 < 6 °C 48 hours 1 L
Turbidity P, G 0 < 6 °C (store in dark) 48 hours 100 mL Hardness P, G HNO3 to pH < 2 6 months 100 mL
Alkalinity P, G 0 < 6 °C 14 days 200 mL Fecal Coliform Fecal coliform P, G 0 < 10 °C 6-24 hours b 100 mL Toxicity Whole Effluent Toxicity P, G 0 < 6 °C 36 hours 10 L
Inorganics
Copper P, G HNO3 to pH < 2 6 months 1 L
Lead P, G HNO3 to pH < 2 6 months 1 L
Silver P, G HNO3 to pH < 2 6 months 1 L
Zinc P, G HNO3 to pH < 2 6 months 1 L
Nutrients
Total Phosphorous P, G 0 < 6 °C, H2SO4 to pH < 2 28 days 100 mL
Total Kjeldahl Nitrogen P, G 0 < 6 °C, H2SO4 to pH < 2 28 days 500 mL
Total Ammonia as N P, G 0 < 6 °C, H2SO4 to pH < 2 28 days 500 mL
Nitrate + Nitrite as N P, G 0 < 6 °C, H2SO4 to pH < 2 28 days 200 mL
Notes:
a. P = polyethylene, G = glass
b. Maximum hold time is dependent on the geographical proximity of sample source to the laboratory
D.2.3 SAMPLE PRESERVATION REQUIREMENTS
Samples collected are preserved in accordance of the methods specified in Table 4b above. D.2.4 CROSS-CONTAMINATION REDUCTION EFFORTS
In an effort to reduce the potential for cross-contamination, the influent and effluent samplers have dedicated collection carboys. All sampling carboys and glassware are washed with laboratory-grade soap, rinsed with tap water, rinsed with distilled water, and dried immediately after use.
D.3 SAMPLE HANDLING AND CUSTODY REQUIREMENTS
Samples are identified, handled, documented, and custody controlled in compliance with the following sections. Samples may be analyzed in the field, CBJ lab, or in a contracted laboratory. Contracted non-Alaska laboratories must be members of the National Environmental Laboratory Accreditation Conference (NELAC) and/or State certified for the respective waste water analytical methods. All sampling equipment and sample containers will be cleaned according to the equipment specifications and/or the analytical laboratory. Bottles supplied by a contracted laboratory are new or pre-cleaned and should never be rinsed or reused. A temperature blank shall accompany each cooler.
D.3.1 FIELD GRAB SAMPLE HANDLING
Field grab samples analysis begins within the timeframe specified on Table 4b where sample collection and analysis information is recorded on laboratory bench sheets or in logbooks.
D.3.2 CONTRACTED LABORATORY SAMPLE HANDLING
Sample containers are provided by the contracted laboratory. Container types and preservatives are listed in Table 4b. Samples are labeled with waterproof ink and prepared as described on the COC. At a minimum, each label will contain the following information:
• Site location
• Sample identification
• Sample type (grab or 24-hr composite) • Date and time of sample collection • Sampler’s initials
• Analyzes required
• Method of preservation (as needed)
Contracted Laboratory for Wastewater Analyzes (Local Drop-off)
Analytical samples are hand delivered to the local contracted lab for wastewater analyzes (Admiralty Environmental, LLC) with complete COC paperwork. QAPP Appendix D contains Admiralty documents, such as the laboratory contract with CBJ, QAM, SOPs, and Microbac’s QAP. Company contact information is as follows:
Admiralty Environmental, LCC. David Wetzel, President 641 W. Willoughby Ave., Suite 301 Hope O’Neill, Manager
Juneau, Alaska 99801 Phone: (907) 463-4415 / Fax: (480) 247-4476 Admiralty prepares a summary report (both written and electronic) of the following findings:
• Title page • COC copies
• QC summary and documentation of any discrepancies affecting system measurement • Sampling and analysis dates
• Test methods
• Method detection limits • Recovery percentages
• QC data (including method blank, MS data, MS duplicate data, and laboratory control sample data)
D.4 SPECIAL TRAINING REQUIREMENTS/CERTIFICATION
The purpose of this section is to ensure that necessary training requirements are known and provided. D.4.1 SAMPLE COLLECTION TRAINING
MWWTP Senior Operators and Lab Technician ensure that all operators are trained in proper sample collection, handling, and analysis techniques. Prior to conducting sampling activities, personnel will review field procedures and sampling requirements discussed in this document to ensure permit required samples are collected and handled appropriately.
D.4.2 METHODS TRAINING
Personnel are required to review the applicable laboratory analysis SOP for all analyzes they conduct. CBJ and contracted laboratory SOPs have been included the current QAPP on file in the lab and at ADEC. Particular attention should be paid to any quality control requirements implemented for the particular analysis.
Figure 3 – Compliance Sample Locations
MWWTP NPDES general water quality parameter monitoring requirements and effluent limits are listed in Table 1a. Fecal coliform monitoring requirements and effluent limits for the MWWTP are shown in Table 1b. Shown in Table 1c are the MWWTP effluent discharged receiving waters monitoring requirements
E. WEEKLY PROCESS CONTROL MEETING
The Weekly Process Control Meeting is designed to keep all operations staff informed about process control decisions at the plant, discuss process issues, to look for changing trends in process parameters and to train new operators. The data for the process control meeting should be readily available in the plant data spreadsheet used at the plant.
Process Control and Compliance Weekly Report
Date: MWWTP
Attending:
Safety concerns:
Permit compliance: Parameter Actual Limit Parameter Actual Limit
BOD 30 pH 6 –8.5
TSS 30
NH3N 1.4 D.O. 6.0
FECAL 200 EFF FLOW 4.0
TRC 0.011 TOTAL P
Process activities since last meeting:
Process Performance:
Unit Process Parameter Target value Actual value Trend New target Actions to take
SBR D.O. MLSS Settleability SVI 125 WAS TSS Digester TS 2% pH > 6.0 D.O. 1.0 Mass Balance
Proposed changes and expected results: Staffing/Scheduling issues:
Energy management: Chemical management: Operations:
Maintenance: Laboratory: Solids Processing: Other:
F. OPERATOR SCHEDULE
The schedule for routine operations tasks has been established to insure the major tasks required for proper operation of the facility and required by the operating permit are completed as required.
Variation in the schedule that are required based on operating conditions will be discussed at the daily meeting during normal work days. Other schedule changes during the normal work day or after hours or on weekends should be reviewed with the Plant Supervisor or Senior Operator to insure that all required tasks are being completed.
The Routine Operator Schedule is included below:
CITY AND BUROUGH OF JUNEAU
WASTEWATER TREATMENT PLANTS
Date of last
modification: 8/05/2014 GT Mendenhall Operations Checklist Week of:
MON TUE WED THUR FRI SAT SUN
6:00 Check plant SCADA for: Any alarms
Jet pump and blower operation in solids tanks Influent valve of E tank in auto
Influent pumps and IPS level status PLC clock correct
Disinfection building screen DO trends
Calculated flow make proc adjust for high flow Check event printer
Monitor SCADA for plant operation throughout the day Check plant for unusual conditions
Check and Change turbidity circular chart Establish press target using press target tool DOB each SBRs before decant phase - record Measure MLSS by Royce
Measure DO in WAS and Thickened tank.
Enter daily plant data into Mendenhall data sheet Check that daily operator task sheet is complete Check any new data for exceedences, (report if any) Enter noteworthy facts in plant log
Calc WAS rate using WAS Calc tool. Set on SCADA Make process changes to SCADA per conditions Check and wash down basins
Calibrate Royce by TSS test
Print Operations W.O.s/ Close W.O.s Set call-out dialer to on call person
UPCP: Influent Screening
Plant: Mendenhall WWTP Location: Juneau, Alaska Author: CJ Schneider Date: October, 2014
Summary
The headworks of any facility should be designed to protect downstream process and
equipment. The Mendenhall WWTF’s headworks include grinding and screening of the influent raw water. The grinder is installed to grind larger debris to aid the downstream screen. The screen is designed to remove solids from the raw waste stream. The captured screenings are then washed, compacted and collected in a trash container.
This section describes the Channel Monster Double Drum (CDD) Series high flow waste management device (Figure 1-1). Included is a description of the CDD, Process overview and drive specifications, defines support guidelines, and summarizes the safety concerns relating to the use and operation of the CDD.
Process Overview
Influent flows by gravity from the sewer line through to the control manhole. It then flows
through the grinder/screener (Auger Monster) into the influent wet well. From the wet well it is pumped into the head-box of the grit removal system, where the pretreatment process is initiated.
The control manhole contains one 36" diameter inlet line, two (2) valved 36" diameter
discharge lines to the SBR plant. By opening and/ or closing the appropriate discharge lines, the mechanical Auger Monster and manual bar rack can be used independently or both
simultaneously.
Flows through the individual screening devices are controlled by opening or closing slide gate valves that control flow from the control manhole. The valves are located in separate channels, ahead of the Auger Monster and bar rack. The slide gates valves are controlled by crank mechanisms at the main floor level.
First, a grinder shreds clumps of rags, sticks, plastics, fecal matter and inorganic/organic material. Next, solids are captured by a perforated plate screen and removed by a rotating auger. As solids are removed, dual wash water zones clean-off fecal material. The rotating auger then conveys solids to the discharge point.
1.0 Influent Screening
The CDD cutter cartridge is an integrated, electrically driven horizontal screen and cutter assembly that screens and reduces raw sewage and solids and serves as an alternative for treatment plant bar screens, rakes, etc. It was specifically designed to fit the existing influent channel width and sit across channel (perpendicular to the influent flow) in the MWWTP Influent Pump Station.
Functionally, when power is applied, the screens rotate horizontally in synchronization with dual counter rotating cutter stacks. The rotating screens directs solids toward and into the cutters where the influent solids are ground into fine particles (to an approx. diameter of .33” x up to 2.5” varying lengths and acceptable to all process pumps) to facilitate free flow and easy disposal of sludge.
1.1 EQUIPMENT SPECIFICATIONS
The following paragraphs define the specifications of the CDD. See the Controller and Drive Assembly manuals for the specifications and details related to the Controller and drive
Physically the CDD consists of the following:
A. Cutter Assembly - Two (2) parallel shafts alternately stacked with individual intermeshing
cutters and spacers positioned on the shaft to form a helical pattern. The shafts counter-rotate with the driven shaft rotating approximately two-thirds the speed of the drive shaft.
The cutter assembly is a 32” (813mm) cutter chamber configuration. The cutters consist of standard 7 tooth cam cutters and spacers stacked on the drive and driven shaft.
B. Screen Drum Assembly - Dual single shaft horizontally rotating screen drums that divert
waste stream solids towards and into the cutter assembly. The assemblies utilize stainless steel perforated screening drums with 1/4” (6mm) circular openings for high capture efficiency.
C. Side Rails - Baffle drum side rails are installed on each screen side of the CDD. The side
rails deflect solids into the cutting chamber. The side rails are concave, follow the curvature of the screens, and extend the full length of the screen assembly.This design provides a rigid structure between end housings to allow the screen and cutter assembly seal cartridges to float, which reduces shaft fatigue. Clearance between the side rails and screen assemblies is set to maintain fineness of grind, uniform particle size, and consistent flow through the CDD.
D. End Housings - Top and bottom end housing protect the screen and cutter assembly
seals and bearings while guiding particles directly into the cutting chamber. The top end housing provides access to the stack tightening nut to enable cutter stack tightening without removing the CDD from the channel.
E. Seals and Bearings - Sealed ball bearings bear the radial and axial loads of the cutter
assembly drive and driven shafts and the screen assembly driven shaft. Each end-housing contains seal cartridge assemblies which, in turn, contain the seals and bearings. Each seal is: independent of the cutter stack and screen, functioning even if the cutter stack or screen becomes loose and remains an integral part of the end housing during almost all maintenance actions.
F. Cutter Stack Tightening - An access cover on the discharge side of the top housing and
an access opening in the top cover allows maintenance personnel to adjust the cutter stack compression for maximum cutting efficiency without having to remove the CDD from the channel or performing any unit disassembly. The adjustment requires power lock out,
removal of the access cover and opening, locking the cutter assembly drive shaft nut through the top housing access cover and torqueing a stack screw through the access opening in the top cover.
G. Frame - An adjustable channel frame and Controller complete the CDD system
Installation. The frame is the enclosure for the CDD assembly. It is lowered into the
channel, bolted into place, and the CDD assembly is lowered into and secured in the frame. H. Controller - The Controller is a power panel, designed to control and protect the CDD. I. Drive Assemblies - An electric motor and gear reducers drive the CDD.
1.2 GRINDER ASSEMBLY
Each grinder assembly is constructed from materials selected for strength, corrosion
resistance, and long life. Cutter shafts are fabricated from two (2)-inch 4140 steel hexagon stock supported on each end by heavy duty sealed Conrad type bearings protected by mechanical shaft seals.
A. Castings are constructed of ductile iron.
B. Cutters are constructed from 4130 steel and thru hardened to 45-50 Rockwell C scale.
C. Bearings/seals: Operating pressure:10 PSI (69 kPa) Maximum. No sealing water required. D. System Weight without drive system components: 1275 pounds
1.3 PROBLEM ANALYSIS
The CDD is designed to operate smoothly and quietly. If ANY excessive noise or
temperature rise is noted, stop operation, and inspect the unit. Table1-1 identifies potential problems and possible solutions. Refer to the Controller and Drive Assembly manuals for potential Controller and Drive Assembly related problems and possible solutions.
Table 1-1
Troubleshooting Guide
Potential Problems
Possible Solutions
Grinder making noise Inspect cutters for burrs.
Check side rails and cutters for evidence that off-center cutter is hitting side rail.
Check for broken cutter or spacer.
Inspect top and bottom seals for any indication of seal failure.
Inspect bearing. Contamination found in the end housing indicates that the seals and bearings have worn and must be replaced.
Check the drive and driven shaft for any indication of a bent or broken shaft.
Cutter stack driven shaft
NOT turning
Check gear key. Replace gear key if broken or missing. Check for broken shaft.
Cutter stack drive shaft not turning
Check for broken shaft below the gear. Cutter stack drive and
driven shaft NOT turning
Check gear key. Replace gear key if broken or missing Check for broken shaft.
Check for broken shaft below the gear
Screen seal failure Inspect bearing/seal assemblies for wear. Replace if wear is indicated.
Potential Problems
Possible Solutions
Cutter stack shaft bobbingup and down
Inspect bearing /seals. Contamination in the end housing indicates that the bearing/seal assembly must be replaced.
Inspect retaining rings and keys. Replace if damaged. Check shaft tightening components. If loose tighten. Cutter stack seal failure Inspect bearings/seal assemblies for wear. Replace if
obvious signs of wear are observed.
Inspect cutters/spacers for wear. If worn thin, replace. Hole worn through a side
rail
Inspect bearing. Contamination found in the end
housing indicates that the seals and bearings have worn and must be replaced.
Check the drive and driven shaft for any indication of a bent or broken shaft.
Screen drum makes noise Inspect screen drum for damage. Do not attempt to repair the stainless steel drum, cage, or shaft stubs. Inspect bearing/seal assembly. Contamination found in
the end housing indicates bearing/seal assembly have worn and must be replaced.
Inspect seals for wear. Replace parts indicating wear. Check the screen drum for any indication of a bent or
broken shaft stub. Do not attempt to repair the stainless steel drum, cage, or shaft stubs.
Screen not turning Check gear drive. Replace defective components. Check for broken screen shaft stub. Do not attempt to
repair the stainless steel drum, cage, or shaft stubs. Screen shaft bobbing up
and down
Inspect bearing/seal assembly. Contamination found in the end housing indicates bearing/seal assembly have worn and must be replaced.
Inspect retaining hardware. If broken replace.
Table 1-2 Design Specifications
Parameter Specification
Wastewater Type Domestic/Commercial
Average Daily Flow (MGD) 3.0
Peak Flow Rate (MGD) 8.5
Flow Channel Width 48”
Flow Channel Depth 48”
Overall Height w/ Motor & Reducer
73.33” (1864) Overall Height w/o Motor &
Reducer
44” (1118)
Weight w/o Motor & Reducer 1275 (580 kg)
2.0 Auger Assembly
This section describes and defines the operation, specifications, and support information related to the auger and its components. Refer to the Controller, Channel/Muffin Monster manuals/instructions for the details on the operation, equipment and options associated with the auger. See Figure 2-1 below for the MWWTP auger/frame installation.
Figure 2-1. Auger Frame Installation
2.1 OPERATION
Operationally, when power is applied to the controller and the auger start cycle is initiated, power is applied to the drive segment and spiral rotation is initiated.
The rotating spiral captures and pulls effluent particles upward, above the channel liquid level, and out the discharge chute. As the spiral rotates, the spiral brush is always in contact with the perforated portion of the stainless steel screen trough to prevent clogging of the
perforations. The screen openings separate liquids and biological solids from the mostly inorganic solid materials. The particulates are carried upward and out of the channel. A spray wash system, mounted over the screen trough, rinses the organic material from the processed solids back into the waste stream, reducing the odor of the particles being discharged.