Attachment 4 Operation and Maintenance Manual 1981.pdf

OPERATION AND MAINTENANCE MANUAL

FOR

SEWAGE TREATMENT PLANT

BOLAR MOUNTAIN RECREATION AREA

LAKE MOOMAW, BATH COUNTY, VIRGINIA

Prepared by:

Gerald E. Coffey, P. E.

Civil Engineering Section Design Branch

Norfolk District, Corps of Engineers 803 Front Street

Norfolk, Virginia 23510 April 1981

CONTENTS

Page Number

I. INTRODUCTION 1

II. DISCHARGE REQUIREMENTS 3

III. UNIT: TREATMENT PROCESSES 9

A. Pretreatment (Septic Tank) 9 B. Flow Equalization 9 C. Rotating Biological Contactor (RBC) 10 D. Secondary Clarifier 12 E. Flow Splitter Box 13 F. Filtration 13 G. Chlorination 14 H. Post Aeration 15 I. Submerged Outfall 15 J. Plant Hydraulics 15

IV. NORMAL OPERATING PROCEDURES 16

A. Manufacturer's Operation & Maintenance Manuals 16 B. Pumping Station Operation 16 C. Septic Tank 19 D. Flow Equalization 21 E. Bucket Feed System 24 F. Rotating Biological Contactor 25 G. Clarifier 29 H. Splitter Box 30 I. Sand Filtration 30 J. Chlorinators and Chlorine Contact Tank 33 K. Flow Meter 34 L. Post Aerator 34 M. Sludge Handling 35 i

CONTENTS (Continued) Page Number

V. SYSTEM RESPONSE AND ANALYSIS 39

A. Rotating Biological Contactor 39 B. Sand Filtration 40

VI. CONTROLS AND ALARMS 41

A. Pumping Stations 41 B. Rotating Biological Contactor and Clarifier 42

VII. SAFETY AND EMERGENCY PROCEDURES 44

A. General 44 B. Emergency Assistance 46 C. Safety Rules 46 D. Safety Program 49 E. Safety Equipment 51 F. Other Safety Requirements 51

VIII. START-UP AND SHUTDOWN PROCEDURES 52

A. Process Start-Up 52 B. Plant Shutdown 54 C. Shutdown Operation and Maintenance 56

IX. SAMPLING LABORATORY PROCEDURES AND REPORTING 58

A. Sampling 58 B. Testing and Laboratory Procedures 59 C. Records and Reporting 64

X. GENERAL MAINTENANCE 66

A. Equipment Records 66 B. Maintenance Scheduling 69 C. Spare Parts and Tools 70 D. Lubrication 71 ii

Follows Page

XI. PLATES

1. Plant Layout 2

2. Bolar Mountain STP Flow Diagram 9

3. Biological Unit 10

4. Biological Treatment Section 10 Splitter Box and Weir Section

5. Feed Well Section, Biological 10

Contact Tank Section, Clairfier Section

6. Chlorination and Reaeration 14

Schematic

7. Sewage Treatment Plant Hydraulic 15 Profile

8. Hydrograph of Type 3 Day Weekend 23

(Holiday)

9. Hydrograph of Type 3 Day Weekend 23 (Holiday) 60% Utilization

10.Flow Equalization Storage Volume 24

Curve

11.Sand Filtration System 30

12.Chlorine Contact Tank Section, 33 Chlorine Dosing Tank and Chlorinators Section, Cascade Aerator Section

13.Chlorinator 33

14.Discharge Curve for 300 V-Notch Weir 34

15.Sampling Bottle 59 iii

Page Number

TABLES

I. Weekly Flows 24

II. Analytical Sampling and Testing Points 60

APPENDICES

A. NPDES Permit

B. Instruction Manual for Autotrol BIO Module Shafts and Autotrol BIO Clarifier Shafts

C. Standard Sewage Siphons for Small Disposal Plants

D. Chlorinators, Instructions, Water-Sure 050

E. Instructions, Stevens Total Flow Meter, Models G1M and G1R

F. Submersible Quick Disconnect Sewage Pumps

G. Sampling and Maintenance Forms

H. References

I. Oil Recirculating Toilets

J. Plant Operator Addition iv

SEWAGE TREATMENT PLANT

I. INTRODUCTION

This manual has been written to provide basic information on operation and maintenance procedures for personnel at the

Bolar Mountain Sewage Treatment Plant. The manual contains a description of the plant, factors that affect its performance, and procedures for maintaining equipment and keeping proper records. Although the manual will be most useful in familiarizing new personnel with the plant and its operation, it is quite important that all plant personnel maintain a familiarity with its content. The manual should be updated as conditions change and additional pertinent information should be inserted, as appropriate, for future use. This manual has been designed to be modified to keep pace with changing treatment system operating and maintenance needs as a result of changes and modifications that accompany the start-up of the treatment plant. In order for this manual to remain a viable tool to operating personnel, present and future, it is imperative that this manual be modified and updated as the need arises.

The plant serves three camping areas, one picnic area, a bathhouse and two trailer dump stations in the Bolar Mountain

Recreation Area which are in use only during the summer months. For this reason, a rotating biological contactor system is utilized with a flow equalization system. The rotating biological contactor is followed by a tertiary filter treatment system to meet effluent requirements. A layout of the treatment plant site is shown on PLATE 1, "Plant Layout".

The plant has a design capacity of 13,000 gallons per day. As a minimum, the plant should be manned two (2) hours per day by a Class III operator.

Job descriptions that outline the Class III operator’s responsibilities and his helpers shall be on file at the site.

Routine work schedules shall be as defined in this manual.

Organizational charts for the operating agency shall be also available as now routinely prepared and updated.

II. DISCHARGE REQUIREMENTS

A. INTRODUCTION

The Federal Water Pollution Control Act, as amended by

Public Law 92-500 enacted October 18, 1972, prohibits any person from discharging pollutants into a waterway from a point source unless the discharge is authorized by a permit issued either by the U. S. Environmental Protection Agency

(EPA) or by an approved State agency, such as the Virginia

State Water Control Board (SWCB). Regulations for the operation of this program are published in the Federal

Register as 40 CFR part 125 (38 F. R. 13528, May 22, 1973) available from the Government Printing Office, Washington, D.C. 20402.

B. NPDES PERMIT

The National Pollutant Discharge Elimination System

(NPDES) Permit contains the authorization to discharge, the effluent limitations, monitoring requirement and reporting requirements. Performance reporting responsibilities are specified in the NPDES Permit. The permitee's reporting responsibilities reside in two areas - monthly reporting and special reporting required in the event of permit violations.

The Environmental Protection Agency (EPA) has issued an

NPDES Permit to the sewage treatment plant which defines the quality of effluent the plant must discharge, and other treatment requirements. The plant must maintain this quality and report monthly to the EPA and SWCB. Reporting requirements are covered in the permit, a copy of which is included herein as Appendix A. The following definitions will aid the new operator, who may not be familiar with the terms used in the permit:

Biochemical Oxygen Demand (BOD) -The BOD test is used to determine the oxygen required to stabilize biologically the organic matter present in the wastewater. It is the principal test to determine the strength, in terms of oxygen required, of municipal wastewater. It is widely used to evaluate the efficiency of various treatment processes and to estimate the effects of pollution on receiving streams. BOD test results are usually reported in milligrams per liter (mg/l) of oxygen consumed at the end of a five-day test period. These results are referred to as the 5-day BOD (BOD5) and should not be confused with the ultimate BOD (BOD5) of the sample.

Chlorine Residual -Chlorine residual is the chlorine remaining in wastewater at the end of a specified contact period (40 minutes) and test results are reported in terms of milligrams per liter. It is used to determine, if desired, that chlorination objectives are being met.

Dissolved Oxygen (DO) -Dissolved oxygen represents the amount of oxygen in solution (dissolved) in a liquid. The solubility of oxygen in fresh waters ranges from 14.6 mg/l at

00 C to about 7 mg/l at 350 C. The solubility of oxygen is at a minimum when temperatures are high. In wastewater testing, dissolved oxygen measurements are used to monitor aerobic conditions in receiving streams and in controlling aerobic treatment processes.

MGD -Million gallons per day.

mg/l -Concentration expressed as milligrams per liter. For use in wastewater analysis this is equal to parts per million (ppm).

pH -pH is a term used to express the intensity of the acid or alkaline condition of a solution. The pH scale is usually represented as ranging from 0 to 14, with pH 7 representing absolute neutrality. Acid conditions increase as pH values decrease, and alkaline conditions increase as the pH values increase.

Suspended Solids -The undissolved substances in wastewater are usually referred to as suspended solids. It is a major parameter in evaluating wastewater strength and in determining the efficiency of treatment processes. It is also used to estimate effects of pollution on receiving streams. It is used with activated sludge mixed liquor testing in determining the sludge density index. This index is an important part of activated sludge process control.

Suspended solids test results are reported in terms of milligrams per liter.

Further descriptions of laboratory tests are given in Section

IX. The discharge permit does not allow bypasses in the event of equipment breakdown, power failure, or any cause other than potential personnel injury or severe property damage. Although standby power equipment is usually provided for treatment plants, such was not needed at this facility since the large storage capacity of the pump stations and flow equalization tank will provide time for restoration of power or so that the recreation facilities can be closed to stop all flow. However, it is strongly recommended that portable generators be obtained and used as a stand-by power source.

C. PENALTIES (Ref 1)

For all violations of the VA-NPDES permit to discharge civil penalties have been provided and for falsification of records and

State reports, criminal penalties have been provided by Federal law.

It is very important that the plant operator be very much aware of these penalties and what constitutes a violation. The operator who signs the Discharge Monitoring Report (DMR) is in essence saying that all information contained on the DMR itself, as well as the information used to prepare the report is correct. He is the person held legally responsible in the event that any discrepancy or falsification of data is discovered. Regardless of who creates the discrepancy or falsification and regardless of whether or not he is aware of it, the operator signing the DMR may be held legally responsible.

A criminal penalty is provided for any and all falsification of NPDES reports. Falsification of tests results recorded on data sheets, whether or not the results have been used for reporting purposes, is considered to be a falsification of State reports as well. Falsification of data on log sheets shows an intent to defraud the State and is considered to be the same as a falsification of the actual report. Upon discovering any falsification or discrepancy in records, the State Water Control

Board transmits all evidence over to the Federal Attorney's Office.

The Federal Attorney handles all proceedings from that point as a

Federal offense. Charges may be filed against the operator who signed the DMR, the plant owner, or both. If found guilty, fines up to $10,000 for each falsification and/or maximum imprisonment of between six months and five years may be assessed. Signing a DMR that has been falsified or falsifying any daily operating data is a very risky business. The State would rather you admit that the required analyses were not performed than make up test results to fill in blank spaces on the daily log sheet.

Civil penalties are provided for any and all violations of the facilities discharge permit. The number and types of violations are many and wide-ranging. Any violation, regardless of type, is punishable by a $10,000 per violation fine. These fines are usually levied against the owner of the facility. Any exception to conditions set by the plants permit is a violation. Violations of permit conditions include but are not limited to: exceeding the flow, BOD or

Suspended Solids average quantities for the reporting period;

having any instantaneous pH reading above or below the permit minimum and maximum (every week the average is above the maximum is a violation); having C12 exceptions exceeding the number of allowable exception; having any D.O. reading below the allowable permit concentration; failing to collect the required samples (i.e. grab instead of composite); failing to collect samples on the required frequencies; failing to perform the analysis according to the correct method, unintentional mistakes committed in calculating averages and quantities on the DMR; or failure to submit the DMR by the tenth of the month. It is a separate violation for each day the DMR is late in reaching the regional office (i.e. five days late equals a $50,000 fine). Each violation of permit conditions carries its own fine as well. As an example, every time the D.O. drops down below the minimum allowable concentration, it is a $10,000 fine. All requirements as set forth in the plants approved O & M Manual should be met since non-compliance with it can be considered to be a violation.

As an example, if the O & M calls for four Class I and eight

Class 2 operators, these numbers of operators must be employed at all times at the plant. Everyday that these requirements are not met is a violation. All requirements set forth in the 0 & M Manual should be met. Normally the SWCB will not press the 0 & M requirements unless the plant gets into operating trouble.

There are other violations but they are too specific to he mentioned here. Normally if the State discovers any violations, they will allow a grace period in which the problem must be corrected.

III. UNIT TREATMENT PROCESSES

An overall layout of the plant is shown on PLATE 1, "Plant Layout". The following sections describe the individual plant units and their function which can be followed on PLATE 2, "Bolar Mountain STP Flow Diagram":

A. Pretreatment (Septic Tank)

The pretreatment facilities consist of a single chamber septic tank, 9,500 gallons. This unit was designed for 12 hours of retention at a design flow of 13,000 gallons per day plus 25% for sludge storage. The principal function of the septic tank is the removal of large solids and dense particulate matter to avoid the lodging of large material in the rotating biological contactor (RBC) media and the settling of dense material in the RBC tankage, both of which would present a maintenance problem. The other functions of the septic tank are (1) some anaerobic digestion of the sludge and

(2) sludge and scum storage.

B. Flow Equalization

Flow equalization is the damping or attenuation of variations in wastewater flows to provide a constant load on the wastewater treatment facility. This damping of peaks in hydraulic loading is accomplished by holding the waste in a structure and releasing it at a constant rate into the RBC unit. The optimum method of loading a wastewater treatment plant is at a constant rate of flow. For example, in this recreational area, flows are highest on weekends and holidays and then drop to much lower levels during weekdays. Large flow variations make the operation of a treatment plant based on biological processes very difficult. Flow equalization solves this problem by providing storage during high flows (weekends and holidays) and releasing the wastes for treatment during low flow periods. This provides a constant hydraulic loading to the plant and makes operation easier and more efficient. The bucket feed mechanism picks up the effluent from the flow equalization tank at a constant rate and applies it to the head or first stage of the RBC unit, see PLATE 3.

C. Rotating Biological Contactor (RBC) (REF 2)

The RBC process is a secondary biological wastewater treatment system. It consists of a large-diameter corrugated plastic media mounted in a horizontal shaft and placed in a concrete tank. The media is slowly rotated while approximately 40% of the surface area is submerged in the wastewater. Immediately after start-up, organisms, present naturally in the wastewater, begin to adhere to the rotating surfaces and multiply until, in about one week, the entire surface area is covered with up to an approximately 1/10-inch thick layer of biomass. This attached biomass contains approximately 50,000 mg/l suspended solids. The biological population present on the plastic media is responsible for the treatment achieved. Flow through the process can be seen on PLATE 3 with a section through the RBC unit shown on PLATE 4 and also on

PLATE 5.

During rotation, the contactor carries a film of wastewater into the air. The wastewater trickles down the surfaces of the contactor and absorbs oxygen from the air.

Organisms in the biomass then remove both dissolved oxygen and organic materials from this film of wastewater. Further removal of organic materials and consumption of dissolved oxygen occurs as the surfaces continue rotation through the bulk of the wastewater in the tank. Unused dissolved oxygen in the wastewater film is mixed with the contents of the mixed liquor to maintain a mixed liquor D.O. concentration.

Shearing forces exerted on the biomass cause excess biomass to be stripped from the media into the mixed liquor as the unit rotates through the wastewater. This prevents clogging of the media surfaces and maintains a constant microorganism population on the media. The mixing action of the rotating media keeps the stripped solids in suspension until the flow of treated wastewater carries them out of the process for separation and disposal. The rotating media thus serves the following functions:

a. provides surface area for the development of a large, fixed biological culture.

b. provides vigorous contact of the biological growth with the wastewater.

c. efficiently aerates the wastewater,

d. provides a positive means of continuously stripping excess biomass, and

e. agitates the mixed liquor to keep sloughed solids in suspension and to provide thorough mixing.

Each shaft of media operates as a completely mixed, fixed-film biological reactor, in which the rate of biological growth and the rate of stripping excess biomass are at a dynamic equilibrium. Treated wastewater and stripped biomass pass through each subsequent stage of media. As wastewater passes from stage to stage, it undergoes a progressively increasing degree of treatment by specific biological cultures in each stage, which adapt to the changing wastewater.

Initial stages of media, which receive the highest concentration of organic matter, develop cultures of filamentous and non-filamentous bacteria. As the concentration of organic matter decreases in subsequent stages, higher life forms including nitrifying bacteria begin to appear, along with various types of protozoans, rotifers, and other predators.

D. Secondary Clarifier

When a liquid containing solid particles is placed in a relatively quiescent state, those particles having a higher specific gravity than the liquid tend to settle. It is the object of this secondary clarifier to remove the suspended solids and return these solids to the septic tank for storage and some treatment. Because the RBC process effluent will generally contain 50 to 150 mg/l of suspended solids, solids loading on the clarifier is quite low. Solid separation occurs by discrete particle settling with no hindered settling or solids compression zones. This means that there will not be a significant sludge blanket as in a clarifier for an activated sludge plant and that the surface overflow rate is the only important factor in the operating efficiency of the clarifier. Since rapid recirculation of the solids is not required for the RBC process as in the activated sludge process, a simple mechanical collector, such as the rotating scoops provided, can be used. As the scoops rotate through the clarifier, they pick up the sludge which flows through the hollow support arms to a flush tank. This flush tank is provided because the sludge is heavy and difficult to transport through the piping. In operation, the scoops will be actually flushed by clarifier water just before the scoops break the water level on its upward swing, see PLATE 5. The flush tank discharges its contents by gravity through the hollow supporting shaft into the septic tank for final storage and some treatment.

E. Flow Splitter Box

The flow splitter box, as shown on PLATE 4, is an open channel with two (2) stop gates. The purpose of this unit is to control the flow from the RBC unit. Depending on which gate is pulled, flow is either recycled through the septic tank or discharged to the sand filters for further treatment.

F. Filtration

Following the secondary clarifier is a gravity sand filter.

The purpose of the filter is to further remove suspended solids and BOD5 from the plant effluent. The wastewater passes down through the filter media which consists of fine sand by gravity. Solid particles are trapped on the filter surface and some between the media particles. As more and more solids are filtered out, the amount of space between the media particles for fluid flow becomes increasingly less causing increased head loss through the filter. When the wastewater above the filter takes too long to drain through the filter, the filter must be cleaned.

A dosing tank or siphon chamber with two automatic alternating dosing siphons is provided for flow distribution on to the sand filters. Each dose has a volume of 1,150 gallons of wastewater and covers one filter to a depth of 4 inches. The average discharge rate is 165 gpm and it will take approximately 7 minutes for the siphon to empty the dosing tank.

Once the wastewater has filtered through the sand, a system of underdrains collect the effluent for coveyance to the chlorinator dosing tank.

G. Chlorination

The supernatant which is discharged from the sand filters enters a chlorinator dosing tank where the water is dosed by gravity through either one or two erosion type chlorinators. This discharge is then collected and routed to the chlorine contact tank for further treatment, see PLATE 6. The purpose of the chlorination is to disinfect the wastewater. Disinfection is the destruction of pathogenic (disease causing) organisms in the wastewater. It is important to differentiate between disinfection and sterilization (a process where microorganisms are destroyed). It would be unnecessary and impractical to sterilize wastewater. Disinfection is necessary to prevent the spread of disease by waterborne pathogens.

Chlorine is used for disinfection because it is highly toxic to disease causing microorganisms. The main elements of effective chlorine disinfection are chlorine residual and contact time.

Chlorine residual is the chlorine which is not used up by elements in the wastewater and is most toxic to microorganisms. Contact time is the amount of time the wastewater is exposed to the chlorine.

Sufficient contact time is necessary to insure that enough organisms have been killed.

The chlorine contact tank also contains a flow recorder/totalizer along with a 300 V-notch weir which will record continuously the outflow from the sewage treatment plant.

H. Post Aeration

Before the effluent leaves the plant, it passes through a post aeration chamber where it is aerated to restore dissolved oxygen which has been depleted during the RBC, filtration, and disinfection stages of the treatment process. The plant discharge permit requires 6.5 mg/l of dissolved oxygen in the treated effluent. The post aeration stage is necessary to insure that this requirement is met. The effluent is aerated by a cascade aeration system which is basically a series of concrete steps. As the fluid falls from step to step, it is exposed to the surrounding atmosphere from which it absorbs oxygen.

I. Submerged Outfall

From the cascade aerator, the flow is discharged into the lake through a single port outfall which was designed to keep the discharge field or plume submerged in the hypolimnion layer of the lake. The outfall line was constructed of 6-inch ductile iron pipe approximately 550 feet long. The discharge elevation is 1550 with

10 feet of sediment storage space beneath the outfall port.

J. Plant Hydraulics

The sewage treatment plant was designed to operate with a very minimum power requirement. To accomplish this, gravity flow was used to convey the waste through the plant with the exception of the bucket feed system from the flow equalization tank, see PLATE 7. By using gravity operated equipment whenever possible and only two motors, plant failures and maintenance can be reduced to a minimum.

IV. NORMAL OPERATING PROCEDURES

A. Manufacturer's Operation and Maintenance Manuals

Routine operating and maintenance procedures for the prefabricated treatment units and mechanical equipment are given in the following Manuals:

MANUAL APPENDIX

1. “Instruction Manual for Autotrol B10 Module B

Shafts and Autotrol B10 Clarifier Shafts"

2. "Standard Sewage Siphons for Small Disposal C

Plants"

3. Chlorinators,"Instructions, Water-Sure 050" D

4. "Instructions, Stevens Total Flow E

Meter, Models GIM & GIR"

5. Submersible Pumps F

The following sections describes in general terms the various components of the collection and treatment system and provides guidelines for their proper operation.

B. Pumping Station Operation

There are two pumping stations which deliver flow to the treatment plant. One is located between the two camping areas at the end of the Bolar Mountain Recreation Access (B.M.R.A.)

Road, (Pump Station No.2), and the other between the Bathhouse and the picnic area also on B.M.R.A. Road, (Pump Station

No.1).

1. Equipment

a. Camping areas (Pump Station No. ?)

Two (2) 10 HP, 1750 RPM, Quick disconnect submersible centrifical sewage pumps, 80 gpm at 59

ft. TDH.

b. Bathhouse (Pump Station No.1)

Two (2) 7-1/2 HP, 1750 RPM, Quick disconnect submersible centrifical sewage pumps, 80 gpm at 48

ft. TDH. 2.

2. Normal Operating Procedures

Pumps at each station are designed to operate automatically. Operation is float (four floats) activated as follows:

a. All pumps cut off and/or alternate at lower level #1.

b. As sewage flows into the pumps station, the level rises until level #2 is reached and the lead pump cuts on.

During normal operations, the pump will pump to level II, cut off and alternate.

c. If the level continues to rise because the lead pump cannot handle the flow, level 13 will be reached and the lag (second pump) will be cut on. Both pumps will then operate until level 11 is reached and both pumps will be cut off.

d. If both pumps cannot handle the flow, the level in the wet well will continue to rise until level #4 is reached and a horn and flashing light alarm will be activated at the pump station.

3. Alternate Operating Procedures

The pumps may also be controlled manually. One pump singly or both pumps may be operated in the manual mode.

4. Emergency Operating Procedures

None of the pump stations have been provided with emergency equipment. In the case of power failure, the wet well should have enough excess capacity to hold one day’s flow. If the flow is excessive or both pumps have failed, then closing of the buildings feeding the pump station is the only alternative. There are three alternatives that maintenance personnel should want to consider doing in the future depending on the extent and type of problems they experience at the pump stations.

a. Power Failures

1. Install a manual transfer switch and a connection for 8 an emergency generator; then use a portable generator to supply power to the pumps. This method of stand-by power is highly recommended.

2. Install an emergency pump connection to the force main, then use a portable pump by dropping a hose in the wet well and connecting to the emergency connection.

b. Equipment Failures

The only thing that can be done is to increase the supply of spare parts including the stocking of a complete spare motor and pump.

C. Septic Tank (Ref 2)

One of the major advantages of the septic tank is that it has no moving parts and, therefore, needs very little routine maintenance. A well-maintained concrete tank should last for 50 years. One cause of septic tank problems involves a failure to pump out the sludge solids when required. As the sludge depth increases, the effective liquid volume and detention time decrease. As this occurs, sludge scouring increases, treatment efficiency falls off, and more solids escape through the outlet. The only way to prevent this is by periodic pumping of the tank.

Tanks should be inspected at intervals of no more than every month to determine the rates of scum and sludge accumulation. Regardless of the inspection programs, a pump-out frequency of once a year is required at the end of the season. Once the characteristic sludge accumulation rate is known, inspection frequency can be adjusted accordingly. The inlet and outlet structures and key joints should be inspected for damage after each tank pump-out.

Actual inspection of sludge and scum accumulations is the only way to determine definitely when a given tank needs to be pumped. When a tank is inspected, the depth of sludge and scum should be measured in the vicinity of the outlet baffle. The tank should be cleaned whenever:

(1) the bottom of the scum layer is within 8 in. of the bottom of the outlet device; or (7) the sludge level is within 12 in. of the bottom of the outlet device. The efficiency of suspended solids removal may start to decrease before these conditions are reached.

Scum can be measured with a stick to which a weighted flap has been hinged, or with any device that can be used to feel the bottom of the scum mat. The stick is forced through the mat, the hinged flap falls into a horizontal position, and the stick is raised until resistance from the bottom of the scum is felt. With the same tool, the distance to the bottom of the outlet device can he determined. A long stick wrapped with rough, white toweling and lowered to the bottom of the tank will show the depth of sludge and the liquid depth of the tank. The stick should be lowered behind the outlet device to avoid scum particles. After several minutes, the sludge layer can be distinguished by sludge particles clinging to the toweling.

Other methods for measuring sludge include connecting a small pump to a clear plastic line and lowering the line until the pump starts to draw high solids concentrations.

Following is a list of considerations pertaining to septic tank operation and maintenance:

1. Climbing into septic tanks can be very dangerous, as the tanks are full of toxic gases. When using the manhole, take every precaution possible, i.e., do not lower an individual into the tank without a proper air supply, and safety rope tied around chest or waist.

2. The manhole, not the inspection pipe, should be used for pumping so as to minimize the risk of harm to the inlet and outlet baffles.

3. Leaving solids in the septic tank to aid in starting the system is not necessary.

4. When pumped, the septic tank must not be disinfected, washed, or scrubbed.

5. Special chemicals are not needed to start activity in a septic tank.

6. Special additives are not needed to improve or assist tank operation once it is under way. No chemical additives are needed to "clean septic tanks. Such compounds may cause sludge bulking and decreased sludge digestion. However, ordinary amounts of bleaches, lyes, caustics, soaps, detergents, and drain cleaners do not harm the system. Other preparations, some of which claim to eliminate the need for septic tank pumping, are not necessary for proper operation and are of questionable value.

7. Materials not readily decomposed (e.g., sanitary napkins, coffee grounds, cooking fats, bones, wet-strength towels, disposable diapers, facial tissues, cigarette butts) should never be flushed in a septic tank. They will not degrade in the tank, and can clog inlets, outlets, and the plastic media of the

RBC unit.

D. Flow Equalization

Proper operation of the flow equalization system is the key to the performance of the sewage treatment plant.

To operate the flow equalization tank only three (3) variables effect its performance:

a. Position of the stop gate in the splitter box, position (1) or (2) as shown on PLATE 4.

b. The flow rate of the bucket feed system as it pumps to the RBC 8 unit which has a maximum of

13,000 gpd or 9 gpm.

c. Inflow to the sewage treatment plant.

Of the above three variables, (a & b) are the only two that the plant operators can control. The third variable, inflow to the plant, will change drastically according to the weather and the time of the recreation season, holidays, etc., or how different areas of the park are utilized each day. To explain the operation of the flow equalization system, two weekends will be examined: a three-day or holiday weekend and a normal weekend with reduced utilization.

The first requirement is to calculate the maximum flow if the park is fully utilized:

AREAS FLOW

Campsites 9300 gpd

Picnic Area 2400 gpd

Bathhouse 6300 gpd

Total Flow 18,000 gpd

Note that this calculated flow is based on state criteria which may or may not actually represent what will he generated when the park is in full operation. For the operators to fully use the flow equalization system, data on the actual inflow to the plant versus the percent utilization of the park will have to he developed. Based on studies at other Corps of

Engineers' Recreation (REF 2), the following flows can he predicted for a holiday (three-day) weekend. Table 1.

TABLE 1

DAY OF % Average Average Daily

WEEK Daily Flow Daily Flow Flow

Monday 66.6 18,000 12,000

Tuesday 27.8 18,000 5,000

Wednesday 20.6 18,000 4,000

Thursday 27.8 18,000 5,000

Friday 50.0 18,000 9,000

Saturday 100.00 18,000 18,000

Sunday 100.00 18,000 18,000

From this data an inflow mass diagram (cumulative inflow) has been developed, PLATE 8. From this inflow mass diagram, the sewage treatment plant discharge will be operated and controlled. The above flow distribution and maximum flow

(100% utilization on Saturday and Sunday) has to be achieved.

From PLATE 8, the two variables that the treatment plant operator has control over can be seen, the first (1) is shown at the bottom of the graph as start discharge and start recycle and the second (2) is shown as flow to the RBC unit or the bucket feed rate.

The inflow hydrograph is for a peak weekend (three day) and should be used to operate the flow equalization tank as follows:

1. Predict, based on experience, the expected utilization of the camping areas, bathhouse and picnic areas for the weekend. If the expected utilization, thus the peak flow, is less than the peak on PLATE 8, develop a new inflow hydrograph based on Table 1 and the percent utilization expected, similar to PLATE 9.

2. Next draw two parallel lines tangent to the inflow hydrograph to equal the pumping rate in the bucket feed system, 13,000 gpd or 9 gpm maximum. The bucket feed system can be adjusted as will be shown on the PLATE 9.

3. From the developed hydrograph, PLATE 8, the operator can calculate that he should start discharge to the sand filters

Friday morning and that there should be about 2,000 gallons in the flow equalization tank when he starts to discharge. This can be determined by placing a staffgage in the feed well and reading the depth, which should be about 1.8 feet. Then from

PLATE 10, the volume can be determined, 2,000 gallons.

4. Every morning the operator should monitor the volume in the flow equalization tank and compare it to the inflow hydrograph. This information should be used to modify any future hydrographs, stop discharge or change feed rate.

5. Wednesday morning, the operator should start recycle.

However, should the flow equalization tank be pumped below the

1 foot mark, water should be added to the system until a good recycle flow is obtained.

PLATE 9, shows how for a typical weekend the inflow hydrograph and plant operation will be changed due to a reduced (60%) utilization of the recreation areas.

E. Bucket Feed System

Only one bucket, with a volume of 5 gallons, will be required initially. Maximum pumping rate will be 5 gallons every rotation of the RBC unit which is rotating at 1.6 rpm or

(5 gallons x 1.6 rpm) 8 gpm. To reduce the flow, plastic inserts in the bucket can be removed thus reducing the volume. When the maximum flow of 9 gpm is required, the five-gallon bucket and arm can be replaced with the 18 gallon bucket, and adjusted to the required flow by removing the appropriate plastic inserts to reduce the volume collected per revolution.

F. Rotating Biological Contactor (Ref. 4)

1. General: Operation of the RHC unit is simple due to the lack of any recycle requirements such as that required for an activated sludge plant. Recycle in the case of the Bolar Mountain plant is to obtain a food source for the biomass on the media during low inflow.

Once the plant is operating, the best control method of the RBC unit is through observation of the biomass on the plastic media and the dissolved oxygen (DO) in the tank or mixed liquor dissolved oxygen.

2. Observation of Biomass: Within the stages of treatment that are accomplishing carbonaceous BOD removal, (stages

1 and 2, see PLATE 3) the biomass, when fully developed, will appear typically as a gray-brown, shaggy mass.

Following initial startup, a thin slimey-feeling biomass will appear. Just after the first week, some biomass stripping may occur, although no apparent decrease in treatment efficiency results. This stripping is normal, and the stripped biomass is soon replaced and the media becomes completely covered with biofilm.

When high degrees of treatment including nitrification are being achieved, the growth in later stages (stages 3 and

4) will be much thinner, less shaggy, and more golden-brown in appearance. The growth will often be irregular in thickness due to the activity of predators, such as protozoa, rotifers, and worms.

3. Mixed Liquor Dissolved Oxygen

The DO content of the wastewater beneath the rotating media will vary from stage to stage. The RBC unit should have a DO greater than 1.0 mg/l and often as high as 2 to 3 mg/l in the first stage. The last stage normally will have a DO approaching 4 to 5 mg/l.

4. Potential Operational Problems

a. Loss of Biomass

Excessive stripping or loss of biomass on the media during the first two weeks of start-up operation is not an unusual occurrence. This event is likely to occur if the unit has been seeded with a biological culture developed in a waste environment different from the operating conditions in the new system. It is also likely to occur if an influent waste containing a toxic or inhibitory substance that kills the biomass, such as chemicals used in recirculating toilets of campers is present. Another possible cause is severe variation in pH.

If severe loss of biomass occurs after the initial start-up period, the following action may be taken:

(1) Determine the concentration, and discharge frequency and duration of the substance that is causing the loss of biomass. Eliminate the toxic substance, if possible. In the event that toxic substances cannot be eliminated, loading peaks should be dampened through the flow equalization system to provide a uniform concentration of the toxic substance which may permit an acclimated culture to develop.

(2) Equalization of the inhibitory substance at the source if possible. Since this is not usually possible, it may be accomplished at the treatment plant through dampening with an aerated equalization system which can be accomplished by adding hydrogen peroxide to the feed well.

(3) Generally, pH in the range of 6.0 to 8.5 will not cause any excessive stripping problems. However, if severe variations, consisting of periods of very low

(below 5) or very high pH (above 10.5) occur, loss of biomass may result. Wastewater neutralization through use of chemicals may be required to insure the influent pH is maintained within a range of 6.0 to 8.5 at all times.

b. Development of White Biomass

The development of white biomass on the media surface can sometimes occur. There is no immediate concern if the white growth (probably thiotrix or beggiatoa) appears only on limited areas of the media.

If, however, this biomass appears to dominate the entire surface, reduced process performance levels may be expected.

White biomass can result when wastewater is received in a septic condition, or has a high hydrogen sulfide (H2S) concentration. High H2S concentrations are sometimes the cause of a predominance of a white filamentous growth on the media. Particularly if, the first stage DO is not large enough that this problem will not develop.

If this condition does develop, it may he alleviated by mechanical pre-aeration of the wastewater or with the addition of hydrogen peroxide.

The dosage is normally determined by a trial and error process.

Another possible cause of white biomass formation is an overloaded first stage in the Bio-Surf system. The solution to this situation is to provide a larger amount of surface area in the first stage. This can usually be accomplished by removing the baffles between stages one and two to increase the total surface area on the first stage.

c. Decrease in Treatment Efficiency

The following are major factors that may affect treatment efficiency:

(1) Reduced wastewater temperature. Wastewater temperature below 55°F (13°C) will result in a reduction of biological activity and a decrease in organic removal. The exact amount of performance reduction will depend on the actual operating load and wastewater temperature. Temperature is a very critical parameter in plants designed to achieve nitrification.

Development of a nitrifying culture under very low temperature conditions can be accomplished, but the time required to achieve maximum Nitrification may be substantial. Experience has shown that 6 to 8 weeks or more are required to achieve steady-state conditions with wastewater temperatures at 45 to 50°F.

(2) pH difficulty. Every wastewater has an optimum pH level for best treatability. For domestic wastewaters, variations in pH between 6.5 and 8.5 will result in little effect on organic removal efficiency. If this range is exceeded at any time, however, a decrease in efficiency is likely to result. When nitrification is required, pH and alkalinity are very critical parameters, and pH should be kept as close as possible to a value of 8.4. The alkalinity level in the raw wastewater should be at least 7.1 times the influent ammonia concentration to allow the nitrification reaction to go to completion without adversely affecting the microorganisms.

(3) If the last two stages don't develop a good biomass for nitrification, it could he due to the low alkalinity of the water. To correct this problem, lime should he added to the septic tank or flow equalization tank; but he careful of the pH and don't exceed 8. Add small amounts weekly to obtain better nitrification.

d. Accumulation of Solids

If grit and primary solids removal is inadequate, which will happen if the septic tank is overloaded, suspended solids may accumulate in the reactor and block passage of wastewater into the media. Substantial accumulation of volatile solids in the reactor may result in the development of odors and may also exert a deleterious influence on process performance.

In the event that a solids accumulation problem develops, the reactor should be pumped free of the solids, and the type and concentration of these solids should be determined to establish the best solution. Contact the

Engineering Department to assist in solving the problem.

G. Clarifier

The suspended solids concentration of the treated wastewater leaving the last stage of media will equal approximately one-third the influent ROD concentration, (SS approximately 194/3 = 65 mg/l). For detailed operation instructions, see Appendix B.

Only a few daily checks are recommended to assure satisfactory clarifier performance.

1. Check flushing action in sludge scoops slightly before they break the water level. If too great or not enough, adjust per manufacturer's manual.

2. Clean effluent weir.

3. Remove any floating material from the water surface.

4. Should the effluent appear to have a high solids content, then do the following:

a. Check alignment and adjustment of sludge scoop, see Appendix B.

b. Clean the small baffle at the inf1uent connection, see PLATES 2 and 3.

H. Splitter Box

Only good housekeeping will be required for the splitter box, periodic cleaning and inspection. Extra gates should be purchased and stored near the plant.

I. Sand Filtration

The dosing tank and siphons should never require any maintenance other than inspection during plant start-up and cleaning at shut-down, see Appendix C.

Dual alternating siphons, (marked "A" or “B") as shown on

PLATE II, dose two of the three filters depending on how the operating valves are controlled. To determine which filters are to be dosed, four control valves have been provided (lA, 2A, 2B and 3B on Plate II). Dosing siphon "A" can only dose filters 1 and 2 through valves lA and 2A, while dosing siphon

"B" can only dose filters 2 and 3 through valves 2B and 3B.

The sequence of operation should be as follows:

1. Open valve lA and close valve 2A; thus siphon "A" will dose filter number 1.

2. Open valve 2B and close valve 3B; thus siphon "B" will be dosing filter number 2, while filter number 3 will be in stand-by or resting mode.

3. Every 3 to 4 weeks rotate the filters. Close valve 2B and open valve 3B; and filter number 3 will now be dosed and filter number 2 will rest. The next sequence would be to dose filters 2 and 1, while resting number 1. In another 3 to 4 weeks, switch to dosing filters 1 and thus starting the sequence over again.

Various techniques to maintain the filter bed may be employed when the bed becomes clogged. Clogged conditions can be determined by logging the time it takes for the dosed effluent to drain through the sand. As the bed becomes clogged, this time will increase significantly and indicate that the filter is clogging. Some of these maintenance techniques include:

1. Resting the bed for a period of time.

2. Raking the surface layer and thus breaking the inhibiting crust.

or,

3. Removing the top surface media and replacing it with clean media.

A section through the filter is shown on PLATE 11. Should any of the material have to be replaced, the following quoted specifications should be used (Ref. 5):

12.2 Filter Material:

12.2.1 Sand shall be coarse, clean and free from clay, loam or organic matter. The sand shall have an effective size of 0.30 mm to

0.50 mm and a uniformity coefficient of not more than 4.0. No more than two percent shall be finer than 0.177 mm (80 mesh sieve) and not more than one percent shall be smaller than 0.149 mm (100 mesh sieve).

Not more than two percent shall be larger than 4.76 mm (4 mesh sieve).

12.2.2 Coarse Aggregate shall conform to Section 203, Virginia Department of Highways and Transportation, Road and

Bridge Specification, Sizes 3, 68 and 8. Crushed limestone will not be acceptable for use as No. 8 aggregate.

12.2.3 Stockpiling of filter media at the site of the

filter, if used, shall be so located that the material will not become contaminated with extraneous matter such as concrete, sand, clay, or dirt. The piles shall he prepared so that withdrawals can be made in a manner that will result in uniform distribution and gradation of sizes of the media throughout the filter. Large, cone-shaped piles or high and narrow piles that would result in appreciable separation of size will not be permitted.

12.2.6 Installation: The filter media shall he carefully

placed in well-leveled layers using wheelbarrows and shovels, and in such a manner as to avoid movement or injury to the underdrains. The media shall be placed as nearly as practicable in final position to avoid excessive rehandling.

Dumping the filer media from trucks directly into the filter, dropping the media from heights exceeding three feet, or throwing the media will not be permitted. Board runways shall be provided for wheelbarrows. After any part of the media has been placed in the filter, the following will be strictly forbidden:

a. Running trucks into or over the filter.

b. Storing materials, such as cement, or placement of construction equipment, such as concrete mixer, inside the filter walls.

c. Installing or using runways or walkways over the filter, except for the purpose of installing material or equipment required in the particular filter.

d. Passing concrete, sand, dirt, or other deleterious material over the filter by any means.

J. Chlorinators and Chlorine Contact Tank

Dual tablet feed chlorinators follow the dosing tank and discharge into the chlorine contact tank after each dose, see PLATES

6 and 12. When the flow first enters the dosing tank, it passes through a stainless steel strainer which removes any large solids that may have gotten into the wastewater stream. This strainer should be checked every week at first and cleaned as necessary.

Tablet feed devices for Ca (OC1)2 tablets (PLATE 13) are constructed of durable corrosion-free plastic. Part of the wastewater flow passes through the dissolving chamber where the amount of chlorine being added is controlled by how much the feed hopper is screwed into the chamber. Tablets are added as required upon manual inspection of the unit. Frequency of inspection will have to be determined by the operator, based on his experience and total treated flow. Manufacturer's operation and maintenance instructions for the chlorinators are in Appendix C. Tablet feed chlorination devices should require less frequent attention than other units, although recent experience indicates that caking of hypochlorite tablets may occur due to the moisture in the chamber.

Caking may result in insufficient dosing of chlorine, but may also produce excessive dosage due to cake deterioration and subsequent spillage into the wastewater stream. Once each month the feed hopper should he taken out and cleaned of any cake deposits or white matter.

Shown in the section through the chlorinators on PLATE 12 is a plug valve in the line to each chlorinator that can be closed…