new york state department of environmental...

Environmental Excellence Awards

New York State Department

of Environmental Conservation

NYSDEC - Env Excel Award Submission Cover (PWWPCD).indd (05/16/12 - 3:46 PM)

Award Submission for

Known as Dvirka and Bartilucci Consulting Engineers

D&B Engineers

Architects, P.C.and

D&B Engineers and Architects, P.C.Submitted by

Port Washington Water Pollution Control District (PWWPCD)

May 2012

- 1 -NYSDEC - Env Excel Award Submission (PWWPCD).indd (05/17/12 - 12:10 PM)


D&B Engineers

Architects, P.C.and

Environmental Excellence AwardsPort Washington Water Pollution Control District (PWWPCD)

Project Summary

The Port Washington Water Pollution Control District (PWWPCD) owned and operated a wastewater treatment plant originally constructed in 1951 utilizing the Trickling Filter biological treatment process with a design flow of 4 MGD. Treated effluent is discharged into Manhasset Bay. The plant was last upgraded in 1987-1989 to achieve secondary treatment levels. As a result of effluent nitrogen restrictions imposed by NYSDEC from the Long Island Sound Study (LISS), the plant was again required to upgrade/modify their treatment system to comply with a strict compliance schedule.

As a result of this project the District improved and provided the following environmental benefits:

• Nitrogen discharge reduction of 68% in the treated effluent

• Elimination of sodium hypochlorite disinfection, therefore 100% reduction of residual chlorine in the treated effluent.

• CBOD

○ Previous performance of 15-20 mg.l (25 mg/l permit limit)

○ Current performance of 2 mg/l (25 mg/l permit limit)

○ 99% removal of influent CBOD

• Total Suspended Solids (TSS)

○ Previous performance of 20-30 mg/l (30 mg/l permit limit)

○ Current performance of 4mg/l (30 mg/l permit limit)

○ 98% removal of influent Total Suspended Solids (TSS)

• Decommission of the 3,000-gallon underground methanol storage tank and elimination of its use as an additional carbon source previously required for the process.

• 100% removal of odorous emissions from the open to the atmosphere distribution chamber, which directed flow to the Oxidation Ditch, by providing underground piping and at the Sludge Thickener Tank by providing a tank cover and odor control system.

• Reclaimed 1.5 acres within the plant grounds and restored the area.

• The project was completed ahead-of-schedule, below the original bid amount and satisfied all Consent Order requirements.

General Project Description

The Port Washington Water Pollution Control District located at 70 Harbor Road, Port Washington, New York is a Special District within the Town of North Hempstead. It is one of the oldest water pollution control districts in Long Island and serves over 28,000 residents and businesses. It has approx. 75 miles of gravity sewers and 17 sewage pump stations.



D&B Engineers

Architects, P.C.and


The bottom waters of the western part of Long Island Sound have, for decades, been deficient in dissolved oxygen at times during the year, resulting in the contravention of water quality standards. The USEPA with the cooperation of the NYSDEC and CTDEP initiated a study in the late 1980’s to identify water quality issues related to the Sound. This effort has come to be known as the Long Island Sound Study (LISS). The study determined that excessive nitrogen discharged from wastewater treatment plants and non-point sources contributed to hypoxic conditions (dissolved oxygen less than 3 mg/L) in sections of the Sound that threaten the aquatic life supported by the Sound. This condition has been the driving force for the nitrogen removal requirements for the North Shore plants. The LISS findings lead to a TMDL (total maximum daily load) reduction of 58.5% for nitrogen for all the WWTPs discharging to the Long Island Sound over a 15 year period, with incremental improvements along the way, ending in 2014. The PWWPCD required SPDES compliance date to achieve this goal was Oct 4 2011.

In order to improve the dissolved oxygen conditions in the Sound, the total nitrogen loading to the Sound, contributed by wastewater treatment plants located on the North Shore of Long Island, the South Shore of Westchester and Connecticut and the Upper East River plants of New York City, must be reduced below a 1990 baseline nitrogen discharge level. As a consequence of this, the Port Washington WPCD new SPDES permit required that total nitrogen levels, (TN) in the plant discharge be reduced by 58.5% by 2013.

The challenge of achieving this goal was demonstrated by converting existing tankage at the plant as a Biological Nitrogen Removal (BNR) Demonstration Project for 1 mgd of flow, (approximately one-third of the plant flow), to provide the interim nitrogen removal and pilot test the use of activated sludge technology at the plant at the same time. This was instrumental in helping with the decision process. For the final full-scale upgrade the District and D&B evaluated seven alternative treatment options, four of which relied on maintaining the existing Trickling Filter technology, to provide the required nitrogen removal. Following a Feasibility Analysis the District ultimately selected the activated sludge oxidation ditch technology as the most cost-effective alternative to provide the necessary treatment. The BNR Demonstration Project, while providing the necessary nitrogen removal, also required a significant amount of methanol, (a 3,000-gallon underground tank was installed for this pilot) and aeration at a significant operating expense, however, the results of the BNR Demonstration Project concluded that the Oxidation Ditch was the best technology for this plant.

The Oxidation Ditch technology utilizes Activated Sludge for secondary treatment or nitrification and accomplishes total nitrogen removal by converting a portion of the front end of the aeration tank to an anoxic zone into which the nitrates produced in the aerobic portion of the tank are recycled. This allows the plant to accomplish total nitrogen removal by relying on the use of the BOD5 in the influent to be a carbon source for the denitrifying organisms in the anoxic zone. In addition to removing the nitrogen from the system by converting the nitrates to nitrogen gas, the denitrifying organisms oxidize the incoming BOD5, reducing the aeration requirement.

The treatment plant utilized sodium hypochlorite for disinfection in the two existing chlorine contact tanks. In addition to the TN requirements, the modified SPDES Permit included a maximum permit “limit” of 0.65 mg/l total residual chlorine for the plant effluent as compared to the previous permit “action level” of 2 mg/l. In order to comply with the new permit requirements, three disinfection alternatives were considered and evaluated. The alternative utilizing a new ultraviolet disinfection (UV) system to replace the sodium hypochlorite chemical addition disinfection was selected.



D&B Engineers

Architects, P.C.and


The construction included the following major components: Installation of new Biological Treatment System – Oxidation Ditch (197’L X 137’W) and appurtenances; Construction of new Final Settling Tank Distribution Chamber; Construction of one new 55-foot diameter 4th Final Settling Tank; Installation of Return Activated Sludge Pumping System and Controls; Installation of new Waste Activated Sludge Pumping System and Controls; replacement of Chlorine Contact Tanks with an Ultraviolet Disinfection System; Modifications to Existing Distribution Chambers; Modifications to the three existing Final Settling Tanks; Installation of new process piping systems; Installation of new Final Settling Tank Mechanisms; Installation of New Emergency Generator; and installation of new Mechanical Bar Screens for influent screening at the Headworks Building , along with other miscellaneous rehabilitation. See attached aerials of the TF plant – Figure 1 and the Upgraded BNR plant – Figure 2.

A summary of the timeline of the project is shown on Figure 3. Beginning with the BNR demonstration project, followed by the engineering study which evaluated all the components and ending with the design phase, approximately one year, which finalized the design process of the full scale BNR based on the pilot, all the regulatory approvals, and lastly, bidding and construction. The construction schedule for this project consisted of 3 years and 3 months for completion. The schedule included milestones for the major components of the project: the Oxidation Ditch and the UV System.

A good track record and construction methods established during the project encouraged D&B and the District to petition the NYSDEC for the early removal of the BNR demonstration project (which was in operation for the nitrogen removal of one third of the plant flow) and one of the Final Settling Tanks. The State accepted the request and permitted interim limits for TN during this phase of the construction. This would shorten the completion of the project by 6 months at a minimum. The State required that Total Suspended Solids (TSS) would not violate the SPDES and the UV system would have an accelerated schedule. During this construction interim period the TSS or TN limits were both in compliance with the required limits, Refer to Figures 2 and 3. This permitted an early project completion along with the environmental benefits. The construction was successfully completed due to the partnering approach between the Engineer, Owner and Contractor used during construction allowing the project to be completed 10 months ahead of schedule, (and within budget). The Construction of the Oxidation Ditch was completed over one year ahead of schedule and the UV system 9 months ahead of schedule, please reference Figure 4.

The design basis for the treatment plant is shown in Figure 5. The design was based on a TN effluent limit of 7.1 mg/l in accordance with the SPDES permit requirements. Historical average Influent and Effluent TN for years 2003-2008 are shown in Table 1 below. Based on the obtained data, the average effluent TN for years 2003-2008 was 20 mg/l. The current average effluent TN with the Oxidation Ditch in operation is 6.5 mg/l, as shown on Figure 6. This results in a successful TN reduction of 68%!

The UV system has performed effectively in the disinfection of the treated effluent surpassing the results of the sodium hypochlorite disinfection. The UV system performance results are shown in Figure 7.

A summary of the outstanding results of the BNR upgrade vs the Trickling Filter Plant for the treated effluent at the PWPCD is shown below:



D&B Engineers

Architects, P.C.and


Parameter Existing Trickling Filter Plant 2003-2008

New Oxidation Ditch Plant

CBOD5 14.9 mg/l 2 mg/lTSS 18 mg/l 4 mg/l

Chlorine Residual 1.5-2.0 mg/l 0 mg/lTN 20 mg/l 6.5 mg/l

Furthermore, the addition of methanol as a carbon source needed for an enhanced performance of the BNR demonstration project was eliminated. Once the performance testing was completed and the obtained results of the Oxidation Ditch were acceptable the introduction of primary sludge was performed. This primary sludge addition as a carbon source proved to be effective and enhanced the results previously obtained. The addition of mechanical bar screens to the process train was also performed during this project. The elimination of the methanol along with the potential hazards associated with handling, storing and dispensing of the chemical is an added environmental benefit as well as a safer work environment for the employees.

In efforts to educate the community, D&B and the District held meetings to provide an understanding and education on the factors that affect the Sound. Although the LISS identified the treatments plants as the major culprit of the nitrogen loading to Manhasset Bay, other contributors also play a role such as non-point sources of pollution. While providing the information to the public about the project, these meetings also assisted in educating the public that we all have to work together to protect our water quality.

Innovation, Sustainability and/or Partnerships

As a result of the change in technology at the treatment plant from the Trickling Filter System to the Activated Sludge Oxidation Ditch technology the plant did not rely or require the use of the existing Trickling Filter system. The Trickling Filters (TFs), therefore, were no longer required and were to be abandoned under this project

The wastewater treatment facility used to operate a biosolids incinerator and a 55-foot diameter by 20 + feet deep Ash Storage Tank, which received biosolids incinerator ash from the fluidized bed biosolids incinerator. When the quantity of ash stored in the tank neared or reached the tank’s capacity it required removal. At the time of the BNR upgrade construction the tank was nearing its capacity and required removal and disposal of the inert ash. D&B and the District requested permission to the NYSDEC involving the use of a waste treatment byproduct, inert ash, in a beneficial way, as fill. The proposed locations for utilization of the inert ash for backfill where around the perimeter of Final Settling Tank #4 and TF #3. The NYSDEC granted the petition, (NYSDEC BUD 933-1-30). Approximately 1000 CY of inert ash were used as backfill at these locations, reference attached 2009 and 2010 Annual Reports. The inert ash was utilized in accordance with the permit requirements. Two of the three TFs where demolished and TF #3 walls were demolished to 1 foot below grade and backfilled with the inert ash per permit requirements. Approximately 1.5 acres of real state within the plant grounds were recovered. The area where the TFs were located was regraded, restored with top soil and seeded with wildflowers. See attached Figure 8.



D&B Engineers

Architects, P.C.and


The positive benefits from the use of the inert ash as backfill translated in terms of cost savings to approximately $200,000 and the elimination of the need to landfill this product or obtain the required fill from another potentially non-renewable source and recover the land within the plant: priceless.

The Oxidation Ditch technology selected to achieve the required goal successfully reduced the amount of total nitrogen (TN) by 68% and chlorine residual (TRC) by 100% in the plant effluent of the PWWPCD. The partnership approach utilized during the construction of this project allowed it to be completed earlier than projected. The early completion provided an earlier environmental benefit to the Long Island Sound.

Superior Practices

The PWWPCD BNR Upgrade project was unique in the way the construction was handled. The participants of the project worked in partnership to achieve the goals of the project. The project schedule was very critical due to this project having a NYSDEC consent order. As usual, in construction there are always challenges, however due to the commitment of the participants of this project, the schedule requirements were met, ahead of schedule providing early benefits to the Long Island Sound… and more as explained below.

In order to ensure the schedules where met additional effort to finding feasible solutions to the challenges of the project were required. As an example, the existing Final Settling Tanks required modification due to the upgrade. The Final Settling Tanks did not comply with “Ten State Standards” for activated sludge systems and needed to be modified to increase the depth from 9-feet to 14-feet side water depth, (5-foot wall height increase). FRP reinforcing was investigated and incorporated into the design to provide the additional required structural support for the existing FST walls which were not adequate for the additional water height – additional hydrostatic pressure. This technology provided time savings as opposed to demolishing and reconstructing the tanks. The addition of this technology as well as the partnering approach utilized through the construction phase allowed the project to be completed ahead of schedule and the benefit of an even earlier cleaner treated effluent to Manhasset Bay!

The project still provided added environmental benefits beyond those imposed by the SPDES permit. The project incorporated under its scope modifications to the process in efforts to counteract odorous emissions to the atmosphere. An existing open to the atmosphere distribution chamber, which received flow from the Primary Settling Tanks and directed the flow to the Oxidation Ditch via a 36” diameter pipe was removed for the process train. The chamber was bypassed by connecting the existing 36” influent pipe from the primary tanks, installing approximately 90 linear feet of buried piping parallel to the chamber and connecting to the existing 36” pipe to the Oxidation Ditch. In addition, included under this project was the installation of a tank cover and odor control system for an existing Sludge Thickening Tank. Both of these additions to the BNR upgrade achieved environmental benefits exceeding the regulatory requirements.

Measurable Environmental Benefits

Ten years ago D&B and the Port Washington Water Pollution Control District started the efforts to reduce the environmental impact from the nitrogen concentrations found in treated wastewater treatment effluent. The journey embarked from a plant that was not designed for nitrogen removal and utilized the typical sodium hypochlorite for disinfection into a construction project to produce a facility which reduces the



D&B Engineers

Architects, P.C.and


amount of nitrogen and residual chlorine in the treated effluent discharged to Manhasset Bay/Long Island Sound. The Long Island Sound Study, (LISS) identified nitrogen discharges from various sources to be the major culprit of low dissolved oxygen levels in the Sound – stress and death of aquatic organisms.

Almost overwhelming at the start of this journey, now better prepared to meet the challenges and continue the improvements for a better environmental performance.

As a result of this project the District improved and provided the following environmental benefits:

• Nitrogen discharge reduction of 68% in the treated effluent – cleaner waters!

• Elimination of sodium hypochlorite disinfection, therefore 100% reduction of residual chlorine in the treated effluent.

• CBOD

○ Previous performance of 15-20 mg.l (25 mg/l permit limit)

○ Current performance of 2 mg/l (25 mg/l permit limit)

○ 99% removal of influent CBOD

• Total Suspended Solids (TSS)

○ Previous performance of 20-30 mg/l (30 mg/l permit limit)

○ Current performance of 4mg/l (30 mg/l permit limit)

○ 98% removal of influent Total Suspended Solids (TSS)

• Decommission of the 3,000-gallon underground methanol storage tank and elimination of its use as an additional carbon source previously required for the process.

• 100% removal of odorous emissions from the Oxidation Ditch distribution chamber (open-to-the-atmosphere), which directed flow to the Oxidation Ditch, by providing buried piping, which eliminated the distribution chamber and also provided a tank cover and odor control system at the Sludge Thickener Tank.

• Reclaimed 1.5 acres within the plant grounds and restored the area.

The District is located in a residential area; this project ensured and provided added benefits to the surrounding community.

Commitment and Leadership of Environmental Excellence

The BNR upgrade project is an example of commitment and leadership in the wastewater industry. The project not only provided the required compliance with the State’s mandates but incorporated a committed effort to improve other practices in order to protect the environment. The project provided cleaner waters and cleaner air. The commitment from D&B and the District propagated through all the phases of the work including the contractor, which provided the tool for an early completion: a partnership



D&B Engineers

Architects, P.C.and


approach. This consisted of meetings and continuous availability from all the partners in order to allow the project to proceed without delay. The construction management for this project provided an outstanding performance in always maintaining one step ahead of the work and in a synchronized fashion, and maintaining communication lines open at all times.

The results were reflected in the early completion, start-up and testing with excellent results. The nitrogen removal and chlorine residual previously discharged into the Sound were reduced and eliminated respectively, odorous emissions were reduced for cleaner air to the surrounding community and the carbon source potentially associated with the operation of the Oxidation Ditch, consisting of methanol, eliminated utilizing primary sludge in its place to further provide benefits to the environment and the PWWPCD’s employees.

Transferability to Other Users

The BNR upgrade was a successful construction project and exemplary for its construction practices. Other similar projects currently under construction are striving to produce similar results as those obtained in this project. As an example, a similar design has been provided for the Great Neck Water Pollution which would expect similar results and benefits.

Funding Sources

The project was bonded for $32,000,000 and fund sources for the project included $11,008,000 from NYS Clean Water/Air Bond Act Grant and a NYSEFC SRF Loan of $15,574,000. The bid contract amount was $23,000,000. The project was completed within budget.

Other Details

In comparison to other processes that achieve similar results in terms of nitrogen removal, the oxidation ditch requires little maintenance. The Oxidation Ditch performance is consistent even with a limited operation and maintenance.

Supporting Information (following this page)

Figure 1 - Plant OriginalFigure 2 - Upgraded BNR PlantFigure 3 - Project TimelineFigure 4 - Actual Construction CompletionFigure 5 - Design BasisFigure 6 - Effluent Nitrogen (TN) ResultsFigure 7 - Fecal Coliform ResultsFigure 8 - Reclaimed Land From Trickling Filters

Figu

re 1

POR

TW

ASH

ING

TON

, NY

POR

TW

ASH

ING

TON

WAT

ERPO

LLU

TIO

NC

ON

TRO

LD

ISTR

ICT

PLAN

TO

RIG

INAL

Figu

re 2

POR

TW

ASH

ING

TON

, NY

POR

TW

ASH

ING

TON

WAT

ERPO

LLU

TIO

NC

ON

TRO

LD

ISTR

ICT

UPG

RAD

EDB

NR

PLA

NT

Figu

re 3

POR

TW

ASH

ING

TON

, NY

POR

TW

ASH

ING

TON

WAT

ERPO

LLU

TIO

NC

ON

TRO

LD

ISTR

ICT

PRO

JEC

TTI

MEL

INE

Figu

re 4

POR

TW

ASH

ING

TON

, NY

POR

TW

ASH

ING

TON

WAT

ERPO

LLU

TIO

NC

ON

TRO

LD

ISTR

ICT

ACTU

ALC

ON

STR

UC

TIO

NC

OM

PLET

ION

Figu

re 5

POR

TW

ASH

ING

TON

, NY

POR

TW

ASH

ING

TON

WAT

ERPO

LLU

TIO

NC

ON

TRO

LD

ISTR

ICT

DES

IGN

BAS

IS

* Req

uire

d to

Com

ply

with

SPD

ES P

erm

it Li

mita

tion

of 2

37 lb

s/d

Figu

re 6

POR

TW

ASH

ING

TON

, NY

POR

TW

ASH

ING

TON

WAT

ERPO

LLU

TIO

NC

ON

TRO

LD

ISTR

ICT

EFFL

UEN

TN

ITR

OG

EN(T

N) R

ESU

LTS

Figu

re 7

POR

TW

ASH

ING

TON

, NY

POR

TW

ASH

ING

TON

WAT

ERPO

LLU

TIO

NC

ON

TRO

LD

ISTR

ICT

FEC

ALC

OLI

FOR

MR

ESU

LTS

Figu

re 8

POR

TW

ASH

ING

TON

, NY

POR

TW

ASH

ING

TON

WAT

ERPO

LLU

TIO

NC

ON

TRO

LD

ISTR

ICT

REC

LAIM

EDLA

ND

FRO

MTR

ICK

LIN

GFI

LTER

S

new york state department of environmental...

Documents