Completed Capital Projects

This upgrade was designed by CDM and included the addition of the fourth aeration basin and a fourth final clarifier to secondary treatment system to provide greater secondary treatment capacity. Based on operating experience and overall growth in flows and loads, the additional aeration basin and secondary clarifier became necessary. It is important to note that the original design criteria did not include the concept of a maximum monthly flow for design purposes. The 1989 NPDES permit indicates the maximum month flow prior to the upgrade was considered to be 43 MGD, and is noted as 52 MGD following the upgrade. Information in the 1989 NPDES permit indicates that average flows in 1987 were 35 MGD and the maximum month was 51 MGD.

This facility planning was initiated after the District’s multiple hearth incinerators were shut down in 1988 to develop a new long-term sludge management plan. In the Final Sludge Management Facility Plan dated April 1998 and prepared by CDM, the projections for design flows and loads to the District were noted as follows:

Although a maximum month condition was not developed as a design condition, the maximum monthly flow in 1996 was noted to be 47.62 MGD and the average daily was noted to be 34.85 MGD. The 1996 maximum month BOD load was noted to be 66,300 lb/d and the 1996 maximum TSS load was noted to be 60,300 lb/d.

The projected sludge production was noted as follows:

The recommended plan from the sludge management facility planning was implemented in two projects. This project was designed by CDM using a conventional design, bid, build approach, and included the new anaerobic digesters, gravity belt thickeners for thickening of waste activated sludge, and centrifuges for dewatering as well as enhancements to sludge storage. All of the sludge handling facilities were covered and exhausted to a new open biofilter for odor control. These facilities are described in detail in the Biosolids O&M Manual.

The drying facility was constructed under a design-build-operate form of procurement, and is currently contract operated by the original developer, New England Fertilizer Company. The facility was designed by Wright-Pierce working with New England Fertilizer Company, and is intended to process design average quantities of 28 dry tons per day and design maximum day quantities of 38 dry tons per day. The facility includes two drying trains utilizing triple pass rotary drum dryers each with the capacity to evaporate 6,000 lbs of water per hour. A single train has the capacity to process 20 dry tons per day when the cake solids are 22%, but capacity increases to 31 dry tons per day when cake solids are 30%. These facilities are described in detail in the Biosolids Drying Facility O&M Manual.

Under an Administrative Order from EPA and DEP, the District moved forward with planning to reduce combined sewer overflows (CSOs) from the 5 CSO overflow structures within the GLSD interceptor system. The Draft Long-Term Control Plan prepared by CDM primarily involves increasing the peak flow capacity of the plant in two phases. The Phase I improvements are to increase the peak flow to 135 MGD. If necessary, the Phase II improvements would increase the peak flow capacity to 165 MGD. The Phase I improvements are projected to reduce the volume of CSOs from an average of 112 million gallons per year to 45 million gallons per year, and the frequency of occurrence of CSOs from 14 times per year to 5 times per year. Following the Phase I improvements, the system will be monitored to determine whether the Phase II improvements are needed.

The District proceeded immediately with facility planning for an upgrade to the WWTF to implement Phase I of the Draft Long-Term CSO Control Plan. This facility planning effort by CDM determined the complete scope of a plant upgrade needed to allow peak flows of 135 MGD to be processed as well as the improvements needed to implement the Phase II plan with a peak flow of 165 MGD. The key elements of the recommended Phase I improvements included electrical feed improvements at the Riverside Pump Station; a new headworks facility to address the high grit loadings associated with wet weather flows and to upgrade the existing screening facilities; and new secondary bypass facilities. The secondary treatment capacity of the facility was evaluated, and projected to decrease from the current peak hourly rate of 110 MGD to 75 MGD due to the increasing loads at the design condition. This resulted in the need for secondary bypass facilities with a future capacity of 90 MGD in order to provide for a future peak flow of 165 MGD.

Additional conceptual planning was carried out by Wright-Pierce. This included significant revisions to the headworks design intended to maximize use of the existing screening facilities, while improving the expected grit removal performance. The District also moved forward with evaluation of alternatives to enhance the secondary system capacity. The final plan included significant improvements to the secondary treatment system including installation of an anaerobic selector at the head end of the existing aeration basins, a new partition wall to allow the aeration basins to be converted to contact-stabilization mode during storm events, and a new fine bubble diffused aeration system. Evaluation of the aeration capacity of the existing mechanical surface aerators had determined that they were of marginal capacity at existing loadings, and an aeration upgrade was an imminent need of the District. It was necessary to convert to fine bubble to implement the process improvements; however, the new aeration system will also result in energy savings compare to upgrading with larger mechanical surface aerators. The secondary system improvements are projected to significantly increase the existing and future secondary treatment capacity and allowed the capacity of the secondary bypass facilities to be reduced. As part of the evaluation, the design flows and loads were reevaluated based on the most recent 3 years of data from 2001 through 2003. The change in design basis is summarized below:

This project implemented the Phase recommendation of the Draft Long-Term CSO control to increase the peak wet weather flow capacity of the plant to 135 MGD. The new facilities were designed by Wright-Pierce, and included a new aerated grit facility, replacement of the existing mechanical bar screens, new secondary bypass facilities, and upgrading of the aeration basins with an anaerobic selector zone and conversion to fine bubble aeration. The following is a detailed listing of the major elements of the project:

1. Aerated Grit Facility:

• New section of force main to connect to new influent channel.
• New influent channel with Parshall flume to measure up to 165 mgd influent flow.
• Two new aerated grit removal tanks designed to accommodate a peak flow of 165 mgd. Tanks will be covered and enclosed within cast-in-place and precast concrete building system.
• Ancillary grit chamber equipment including aeration system and clamshell and hoist grit removal system.
• Ancillary building spaces of masonry construction and equipment including truck bay with oil/water separator for drain; permanganate room with permanganate feed system; utility room and heating and ventilation equipment; and electrical room with MCCs and controls.

2. Influent Screening Facility:

• Replace the existing screens with three new mechanical bar screens each with 3/8″ bar spacing.
• Three new screening wash presses to wash and compact the screenings.
• New electrical and control room with separate heating and ventilation system.
• New power feed from main switchgear in Electrical Building to new transformer and motor control centers at the new electrical room in the Screening Building to feed head end of WWTP including the Screenings Building, Primary Clarifiers, and new Aerated Grit Facility.

3. Odor Control System:

• Proprietary bio-scrubber to treat exhaust of Aerated Grit Facility and Septage Receiving.
• Exhaust fan and ductwork to draw from Aerated Grit Facility and Septage Receiving to new odor control system.

4. Secondary Treatment System:

• Upgrade the existing secondary treatment process to the Anaerobic Selector with supplemental Contact-Stabilization Storm Mode. Construct new concrete walls to create selector at head end of each existing aeration tank compartmentalized into three zones. Provide submersible mechanical mixers for each zone of each selector. Provide new openings from primary effluent channel into aeration tanks complete with new gates.
• Replace the existing mechanical surface aerator system with a fine bubble diffused aeration system consisting of fine bubble diffusers fed by PVC manifolds in aeration basins with stainless steel distribution piping.
• New masonry Blower Building with four multi-stage centrifugal blowers to deliver air to new diffused aeration system complete with new electrical room feed from main service entrance to facility.
• New power feed from main switchgear in Electrical Building to new transformers and motor control centers at the new Blower Building.
• All necessary piping and appurtenances for a complete system.
• Repair areas of deteriorated concrete and control and expansion joints in aeration basins.

5. Secondary Bypass:

• Secondary bypass structure incorporating flow measurement, control of adjustable weirs and hypochlorite injection through submersible induction mixer for disinfection.
• 60-inch secondary bypass pipe from bypass structure to bypass contact tank
• Bypass contact tank complete with hypochlorite injection at head end of bypass contact tank through submersible induction mixer, and sodium bisulfite injection at discharge end.
• Bypass outfall structure tying in bypass outfall to the main plant outfall.
• Masonry wall at Plant Water Pump Station and new heating and ventilation system.
• New hypochlorite feed pumps in basement of Process & Maintenance Building drawing from existing hypochlorite storage tanks and piping to application points.
• New sodium bisulfite feed pumps in first floor of Plant Water Pump Station drawing from new sodium bisulfite storage tank and piping to discharge end of bypass contact tank.
• New sampling pumps and residual chlorine analyzers.

6. Riverside Pump Station:

• Furnish cooling fans for existing transformers.
• New soft starter for one of the 800-hp influent pumps.
• Various control system improvements.
• New manual operators for influent sluice gates.

7. Outfall Structure:
Removal of certain structural elements related to former hydroelectric project including widening orifice at base of vortex structure, to reduce headloss sufficient to avoid flooding weirs of chlorine contact tanks at future 165 MGD peak flow.

8. Structure 6+90:
Remove 24″ by 48″ sluice gate and frame, wall thimble, wall plate and concrete grout to provide a 5′-0″ wide by 5′-6″ height clear opening.

These projects implemented recommendations from the April 2009 Energy Evaluation. The following is a detailed listing of the major elements of the project that were provided.

Contract No. 2009-1 (2010) $600,000:

1. New variable frequency drives (VFDs) on existing Anoxic Zone “Y” Mixers (Mixer Nos. MX-315, MX-325, MX-335, and MX-345).
2. New VFDs and motors on existing Return Activated Sludge Pumps (RAS Pump Nos. 1-6).
3. New VFDs and motors on existing Waste Activated Sludge Pumps (WAS Pump Nos. 1-4)
4. New VFDs and motors on existing Primary Sludge and Grit Pumps.
5. New VFD and motor on existing Odor Control Fan No. 2.
6. Instrumentation and controls work.

Contract No. 2009-2 $1.2 Million:

Miscellaneous energy efficiency improvements related to new hot water and heat boilers that are fueled by either biogas or natural gas. Other miscellaneous HVAC efficiency upgrades including new thermostats.

Contract No. 2009-3 $500,000:

1. New variable speed Plant Water Pumps (Pump Nos. 1-4) and 10-inch magnetic Plant Water flow meter.
2. New motor actuators on existing aeration butterfly valves in Aeration Tanks Nos. 1-4 Zone B (BFV-313-07, 313-08, 323-07, 323-08, 333-07, 323-08, 343-07, 343-08).
3. New Condensate Water Feed Pumps (Pump Nos. 1-2) and 4-inch magnetic Condensate Water flow meter.
4. New Blower Building power meters.
5. Instrumentation and controls work.

Contract No. 2009-4 (2011) $2 Million

Installation of 410 kW of solar photovoltaic systems

CWP 11-13 Plant Improvements $2.7 million

Replacement of primary clarifier mechanisms and added additional diffusers to aeration system to increase aeration capacity.

CWR 11-14 Riverside Pumping Station Modifications and 72-inch Force Main Replacement (2012-2013) $11 Million

This project (CWSRF No. 3491) was implemented in accordance with recommendations identified in the June 2010 Long-Term CSO Control Plan, more specifically; the flow capacity of the RSPS and WWTP will be increased from 135 MGD to approximately 167 MGD. Additional work regarding the pumps at the RSPS will be completed in the future in order to achieve these flows and this work was not included as part of this Contract. The work performed under this project was designed by Kleinfelder, and included a new 72-inch force main, replacement of pump discharge piping and header internal to the RSPS, replacement of pump discharge knife gate valves, and new surge control system. The project also included replacement of the volute, impeller, impeller shaft, suction disk wear ring and other related appurtenances for Pump No. 2. The following is a detailed listing of the major elements of the project:

1. 72” Force Main

• 72-inch Steel Force Main from RSPS header STA. 700+00 to STA. 700+88 with cathodic protection.
• 72-inch Centrifugally-Cast Fiberglass Reinforced Polymer Mortar (CCFRP) Force Main “HOBAS” from STA. 700+88 to STA.724+14.
• Two (2) trenchless crossings by means of jacking 96-inch casing of the existing PCCP force main at STA. 702+38 to 703+85 and railroad at STA. 704+69 to 705+60.
• New force main with connection to the existing “west” stub (PCCP) of the influent structure at STA. 724+14.
• Influent channel slide gates on both the new 72-inch CCFRP force main and the existing 72-inch PCCP force main.

2. Riverside Pump Station:

• Replacement of Pump No. 2 (1250 HP) volute, suction disk, impeller, shaft and associated hardware.
• Installation of replacement parts for Pump No. 3 (1250 HP), including a new suction disc and lower wear ring (installed by general contractor); and a new impeller, wear ring, shaft and shaft bearings (provided and installed by the GLSD).
• New discharges for Pumps No. 1 through 4 including new check valves and knife gate valves.
• New bypass plug valves for Pumps No. 1 and 4.
• Elimination of hydraulically actuated surge control valves on all four (4) pump discharges.
• New steel header 42-inch to 72-inch in diameter.
• New air compressor for existing bubbler level transducers (total of 2) for the wetwell (Indication only).

3. Surge Control System

• 25,000-gallon hydropneumatics tank
• 48-inch steel inlet/outlet pipe with knife gate isolation valve
• Two (2) air compressor systems
• Associated air piping for level control and plant water piping for flushing
• Differential Pressure Transducers, Pressure Transmitter, and other associated instrumentation
• Control panel and electrical connections

This project provided the inspection and cleaning of all three anaerobic digester to improve operability and extend the life of the infrastructure. A fabricated metal gutter system with downspouts (one existing and two new) was installed at the top of the digester walls to capture any foam which may originate from the tank. This gutter system utilizes metal plating on the inside and outside face of the tank as walls of the gutter while the top of the existing concrete walls will serve as the base. This downspout piping will convey flow from the gutter down to a new subsurface pipe around each digester which will convey flow to the existing digester overflow pipeline. In addition, a new connection will be designed through the wall of the digesters and into the new downspouts to provide a new high-level outlet at an additional two locations (while reusing the existing overflow through-wall connection) for each tank.

A secondary containment system including a precast concrete highway (“jersey”) barrier installed partially buried to provide a catchment area for any foam that may escape (or be diverted from) the primary containment system. A joint sealant system will also be specified as part of the contract. To facilitate cleaning of the secondary containment and prevent any infiltration of materials into the subsurface environment, cast-in-place concrete has been installed.
Emergency Diversion Valves are installed on the vertical downspouts to allow for relief of any surcharging within the conveyance system which may occur due to plugging. Sumps are located within the secondary containment to facilitate pumping of materials within the secondary
containment.

Lastly, repairs to existing draft tubes were completed.

A new cover monitoring system was installed to determine and supply levels of all three digester covers.

This project includes the installation of improvements to increase pumping capacity at the Riverside Pump Station. Major aspects of the project include maintenance of the existing pump station operations, mechanical, electrical, and instrumentation equipment rehabilitation or replacement. The project also includes modifications/demolition of existing concrete equipment pads and installation of underground electrical duct banks. New, larger impellers were added to all pumps and spares as well as the ability to adjust the speed of the smaller, 800 Hp pumps. Speed controls were replaced on the larger 1250 Hp pumps. New electric operators were added to the four discharge valves.

This project was partially funded by the Clean Water Trust, Department of Energy Resources and National Grid.

The major components of the project include new organic waste receiving tanks and pumping systems, new anaerobic digestion feed pumps, a new 1.4-million-gallon digestion tank along with ancillary mixing and heating equipment, biogas conveyance and waste gas burner, biogas hydrogen sulfide and siloxane treatment systems, biogas pressure boosting system, two -1.6 MW combined heat and power engines with Best Available Control Technology (BACT) exhaust treatment. The power produced from this system will be utilized at the wastewater treatment plant first and any surplus will be “net-metered” to the electrical grid to offset costs at the off-site Riverside Pumping Station. In addition to providing the electrical needs at the treatment plant, this system will serve as the emergency power generation system if the electrical grid is experiencing brown or black outs.

This project was partially funded by the Clean Water Trust, MassDEP, Mass Clean Energy Center, Department of Energy Resources, and National Grid’s CHP Incentive Program.

On October 14th, 2022, sealed bids were opened for the rehabilitation of the Greater Lawrence Sanitary District Biofilter. The project involved removing, disposing, and replacing the existing biofilter media and crushed stone of the underdrain system. Additionally, 60 biofilter leachate pipes were replaced, and two new cleanouts were installed in the odor control piping system. The Biofilter was upgraded with a long-lasting media made of gravel, sand, and soil blend, rather than the conventional woodchip mixed media. The substantial completion of the project was achieved on August 8, 2023.

The District (GLSD) has two biological filters (biofilters) used to treat and remove odors from various areas in the plant. One filter is a stacked tower that uses plastic media. The other uses a combination of gravel, sand, and soil as media. A biofilter is not a traditional filter and does not function like a particulate filter. In the case of GLSD, odorous air is blown through the media. The media provides a habitat for microorganisms and bacteria to grow on. The bacteria produce a biofilm. The odor compounds are adsorbed on the surface of the media by the biofilm, and the odorous compounds are broken down.