Treatment Facility and Collection System History:

Construction of the first public system of sanitary sewers and of the treatment plant began in 1966 and was designed to be expandable to meet the growth of the Town of Billerica's population, which was estimated to be 50,000 by the year 2,000.

The original Wastewater Treatment Facility was designed to treat .8MGD (million gallons per day), by using aeration tanks and final settling tanks followed by chlorination before discharge into the Concord River. In 1975 the first upgrade took place which, doubled the aeration tank capacity, added an additional final settling tank and added a sludge disposal building which housed a coil vacuum filter for sludge thickening. This upgrade brought the plant capacity to 1.6 MGD.

In 1982, a return sludge building was added to house the sludge return pumps which had been externally mounted on the final settling tanks.

In 1984, the Town of Billerica's landfill was closed which was where the thickened sludge was disposed of. We began hauling liquid sludge by tanker truck to Greater Lawrence and then to Upper Blackstone Abatement Facility.

In 1988, construction began on the next expansion which would bring the Wastewater Treatment Facility to it=s present size of 5.5 MGD.

New Facilities:

The new facilities include: preliminary treatment (mechanically cleaned bar screens, grit removal equipment); primary treatment (3-60' diameter primary settling tanks, primary sludge pumps, primary scum pumps, primary sludge holding tank); replacement of the mechanical aerators in the aeration tanks with a diffused aeration system; 3-60' diameter final settling tanks; 3 recirculated sludge pumps; secondary scum pump; new chlorination equipment; post-aeration facilities; plant water system improvements; blended sludge holding tank; sludge transfer pumps; new dissolved air flotation thickener; 2-2 meter belt filter presses; associated polymer storage, transfer and conditioning equipment; sludge conveyors; composting facility and storage areas and a new Administration and Maintenance Building, which houses the Plant Superintendent's office, control room, laboratory, personnel facilities, aeration blowers, maintenance shop, garage and emergency generator.

Wastewater Treatment Plant Data

Plant type - Grade 7 secondary Treatment with full composting abilities.

Flow - Average daily flow is 3.1 MGD, (includes .40 MGD industrial flow)

Designed for 5.5 MGD

Plant Lab Results

Average BOD5 - In 146, Out 7 Average 95% Removal

Average Suspended Solids - In 161, Out 10 Average 94% Removal

Collection System - 19 pump Stations with 172 miles of sewers. Additional miles of sewer added yearly.

Population Served - 65% of the Town population is sewered.

Town Population - 38,000 residents (24,700 residents served)

Plant Equipment

Mechanical Bar Screen - grit removal - 3 primary clarifiers - diffused air aeration tanks - 6 final clarifiers - chlorine tank - post aeration tank - 3 sludge housing tanks - 2 diffused air flotation thickeners - 2-2 meter belt filter presses - 12 - 200 cubic yard bins - 24,000 square feet uncovered compost storage area.

Plant Staff And Licenses

Plant Superintendent- (Gr. 7), Grade V Operator- (Gr. 7), Maintenance Supervisor-( Gr. 4.), Lab Technician- (Gr.7), 7 Licensed Operators (1-Gr. 7, 1-Gr.6, 5-Gr.4), 9 Maintenance Men (1- Gr. 7, 1-Gr 4, 2-Gr. 1), Principal Clerk

21 Personnel total, operation is 365 days per year, 24 hour per day , 7 days a week.

Preliminary Treatment

Mechanically-Cleaned Bar Screens - remove floating and/or large objects that could either clog or damage downstream equipment.

Grit Removal Chambers - remove sands, gravel and other heavier inorganic solids from the wastewater flow into the plant.

Parshall Flumes - measure the wastewater flow into the plant.

Primary Treatment

Primary Settling Tanks - remove virtually all settable solids and approximately 60 percent of the suspended solids, grease and oil. The settled solids are pumped to the primary sludge holding tank and the floatables flow by gravity to the primary scum well and are then pumped to the scum concentrator.

Secondary Treatment

Aeration Tanks - Organic pollutants are removed by micro-organisms cultivated under aerobic conditions. Oxygen to support the biomass is supplied by a fine bubble diffused aeration system.

Final Settling Tanks - Receive the aeration tank discharge (mixed liquor) containing the biomass and separate the solids from the liquid. An appropriate amount of the settled activated sludge is pumped back to the aeration tanks and the excess is wasted and pumped to the sludge handling facilities for thickening.

Disinfection

Chlorination - treated wastewater flows through one or two detention channels after being mixed with a solution of chlorinated water to achieve disinfection of final effluent by reducing pathogenic bacteria and viruses to safe levels.

Post-Aeration

Post-Aeration Tanks - the dissolved oxygen content of the treated wastewater is increased by the addition of air supplied by a fine bubble diffused aeration system.

Sludge Thickening

Dissolved Air Flotation thickeners - receive waste activated sludge (WAS) directly from the biological treatment system and thicken the sludge from about 0.5 percent solids to about 4 percent solids; thickened sludge then flows by gravity to the WAS storage well.

Sludge Dewatering

Belt Filter Presses - thickened WAS and primary sludges are blended, polymer conditioned and dewatered to about 25 percent solids.

Sludge Stabilization

Aerated Static Pile Composting - sludge cake from the belt filter presses is transferred by conveyors, blended with a bulking agent (wood chips or wood ash) to reduce its moisture content; increase porosity and facilitate materials handling; and is then placed in one of 12 concrete bins. Each bin is loaded to form a pile which is aerated by blowers and perforated piping to enhance aerobic decomposition and stabilization of the sludge.

Curing and Storage Area - after the sludge/bulking agent mixture is allowed to actively compost for 14 to 21 days, the material is subsequently stockpiled in the storage areas adjacent to the Composting Building, where it is allowed to cure for an additional time before it is transported offsite for final disposal. The end product may be marketed for beneficial use such as landscaping or conditioning poor quality soils.

Problems Overcame/Success Achieved:

Composting started in Billerica in August of 1990 after the plant upgrade had been finished. In March of 1992, odor problems and complaints had closed down the composting operation. Liquid Sludge had to be hauled (at $.03 cents a gallon) to Upper Blackstone WWTF which had to be treated and incinerated (at $250.00 per dry ton) All of these additional costs added up to $175,000.00 for the year. In addition to all of this, the surrounding neighborhoods had formed an Odor Control Committee and were very vocal at Town Meetings. They were able to generate local newspaper interest in their story and this caused the shutdown of the composting operation.

In the fall of 1992, the Town of Billerica Wastewater Treatment Facility (WWTF) started experimenting with woodash as a bulking agent instead of wood chips (which has been used in the original start-up). With cooperation of the Odor Control Committee, the WWTF started composting at 50% capacity to show the plant could eliminate odors with a change in the bulking agent. By February of 1993, odor control had been successful and the WWTF started composting at 100% capacity. The WWTF had generated between 6,000 and 8,000 cubic yards of Type I Compost per year since 1993, due to the inception and use of woodash and sawdust as a bulking agent.

In May of 1997, the Town of Billerica Wastewater Treatment Facility submitted an application to the EPA for the "Beneficial Use of Biosolids Award". This is a ten year old program that recognizes the outstanding efforts to promote the beneficial use of biosolids. The Billerica WWTF won third place and became the only Massachusetts facility to win a National Beneficial Biosolids Award in the history of the program. The award was officially received October 20, 1997 at the EPA Wastewater Management Excellence Ceremony in Chicago by the Superintendent of the Billerica Wastewater Treatment Facility, Arthur Malcuit.

Contact Information

Billerica Wastewater Treatment Plant
70 Letchworth Ave.
No. Billerica, MA 01862

Tel. 1-978-671-0956
Email Bilwwtp@aol.com

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