PHaSe I

Atlantic Treatment Plant Expansion
Detailed Information
Phase I
Average Day
44 MGD
Maximum Month
54 MGD
Peak Process
108 MGD
Peak Hydraulic
135 MGD
Future Maximum Month
72 MGD
Future Peak Process
144 MGD
Future Peak Hydraulic
180 MGD
MGD
Design Flows
BOD (Maximum Month)
286 mg/l
TSS (Maximum Month)
162 mg/l
TKN (Maximum Month)
44 mg/l
Future Peak Hydraulic
Peak Hydraulic
Design Influent Concentrations
Future Peak Process
Peak Process
Future Max. Month
Maximum Month
Average Day
200
175
150
125
100
75
50
25
0
Key Statistics
Design Capacity >> 54 MGD, with provisions for a future expansion to 72 MGD. Increased from 36 MGD.
Construction Cost >> $164 million
Construction Duration >> March 2006 - August 2011
Design Effluent Limits
Monthly Average
(1)
Weekly Average
Min.
Max.
20,280
--
--
45
20,280
--
--
--
4.0
--
1.0/0.1
--
200
--
--
--
--
--
Enterococci (N/CML)
35
--
--
--
--
--
pH
--
--
--
--
6.0
9.0
MG/L
LB/D
MG/L
LB/D
BOD
30
13,520
45
TSS
30
13,520
Total Residual Chlorine
2.5
Fecal Coliform (N/CML)
(1)
36 exceptions per month/0 exceptions per month
Key Design Features
Secondary Treatment >> Replaced high purity oxygen system with new diffused aeration tanks that use a hybrid blower system.
The high-efficiency, single-stage blower reduces life cycle costs.
Solids Processing >> A two-phase, acid-gas digestion process to stabilize biosolids, reduce biosolids, reduce pathogens, and
generate usable biogas for energy.
Solids Handling System >> New gravity belt thickeners. Centrifuges relocated to a new building adjacent to the cake storage
pad, eliminating cake hauling operations.
Reuse System >> The Dam Neck Naval Facility uses plant effluent as a heat sink for building heating and cooling.
Primary and Secondary Clarifiers >> New collector mechanisms and coatings.
Key Project Benefits
Optimizing Operations >> Expanded plant without increasing staff.
Hampton Roads Sanitation District
08/2013
www.hrsd.com
Construction Cost Savings >> Soil pre-consolidation using on-site material saved over $23 million in construction costs
compared to deep pile foundations.
Consumer Cost Savings >> Residential ratepayers will continue to enjoy an advanced wastewater treatment system that
protects public health and the local waters for less than a dollar a day.
Additional Capacity to Handle Flows for the Next 20 Years.
Solids Processing
Wastewater Treatment
1. Preliminary Treatment Facilty
Force Mains
from Virginia
Beach and
Chesapeake
Screens
2. Primary Clarifiers
8. Gravity Belt
Thickeners
9. Two-Phase Digestion
Waste
Activated
Solids
Grit Collectors
Screenings & Grit to Landfill
Primary Solids
Acid
Phase
10. Digested Solids
Storage
Biogas
Converted to
Plant Heat &
Electricity
Gas Phase
Blowers
7.Effluent
Reuse
3. Aeration Tanks
Waste
Activated
Solids
4. Secondary Clarifiers
1. At the Preliminary Treatment Facility, wastewater
passes through screens to remove solid debris
and floating material, such as rags, paper, plastics,
and metals that could cause problems later in the
treatment process. Most of the removed materials
are sent to a landfill. Next, grit removal facilities
eliminate sand, gravel, and other solid materials that
are heavier than the organic biodegradable solids in
the wastewater.
2. Next, wastewater flows to the Primary Clarifiers.
These rectangular tanks reduce the flow velocity and
allow suspended material to settle to the bottom.
Scraper blades called “flights” simultaneously scrape
the primary (untreated) solids from the bottom and
skim the grease from the top. The solids receive
further treatment in the solids handling facilities.
3. At the Aeration Tanks primary effluent flows into
these aerobic treatment basins where bacteria break
down contaminants even further. Blowers located in
the Blower and Electrical Building provide air to the
microorganisms.
Non-Potable
Water for
Plant Use
5.Chlorine
Contact
Tanks
6.Effluent
Pumps
Atlantic
Ocean
4. The microorganisms are separated and
returned back to the Aeration Tanks in the
Secondary Clarifiers. Revolving “arms”
simultaneously withdraw the concentrated
microorganisms from the bottom and skim the foam
from the top. The solids receive further treatment in
the solids handling facilities.
5. Clear effluent from these circular tanks, is
called secondary effluent, and flows to the
Chlorine Contact Tanks. Here chlorine is added to
kill disease-causing organisms before the water is
released back into the environment.
Centrifuges
11. Dewatering
12. Cake Storage
8. Waste activated solids collected from the Secondary
Clarifiers are processed through Gravity Belt
Thickeners to remove excess water.
9. In the solids handling facilities,
Acid-Gas Phase Digesters process
the solids. Within the heated tanks,
microscopic bacteria digest the sludge
and break it down into stable organic matter, which is
used in agricultural application.
10.Digested Solids are temporarily stored in a holding
tank prior to dewatering. This storage allows the
13. Land Application
dewatering system to be operated during off-peak
hours, reducing energy costs.
11.The digested solids are Dewatered in centrifuges
to further remove excess water and achieve a solids
concentration of 18 to 20 percent.
12.The dewatered Cake is stored on one of two pads for
up to three months prior to land application.
13.When weather conditions are suitable, the dewatered
cake is hauled to local farms for Application as a soil
conditioner and fertilizer.
6. The final Effluent is pumped through an outfall pipe
and discharged into the Atlantic Ocean 1½ miles
offshore through a diffuser pipe to ensure thorough
mixing.
7. A portion of the final effluent is Routed through heat
exchangers at the Dam Neck Naval Facility to provide
energy-efficient building heating and cooling.
At la nt ic Tre at m e nt P la nt Ex pa ns ion Phas e I
13
Things You Ought to Know
HRSD At la nt i c Treat ment Pl ant (AT P ) Co m b i n e d H e at an d Powe r System
1. HRSD’s first combined heat and power (CHP)
project.
2. Uses anaerobic digester gas produced in the ATP
treatment process, which is similar to natural gas, to
generate renewable power and heat.
3. Allows 100% beneficial use of ATP digester gas;
previously, more than half the gas was wasted.
4. The CHP system includes digester gas treatment
and two clean-burning, 1.1 megawatt (MW)
engine generators.
5. Robust digester gas treatment reduces wear and
tear and maintenance on the engine generators.
6. An innovative biological treatment process for
removing corrosive hydrogen sulfide, one of the
largest of its kind in the US, reduces the cost of gas
treatment.
7. Heat from the engine cooling system and exhaust
is captured for digester and building heating.
8. Will produce almost 15 million kilowatt hours
per year of renewable power.
9. Power is used on-site to meet almost 50% of the
ATP’s electricity demand and shave almost $650,000
from the annual electric bill.
1 0. Electricity produced is enough to power over
1,200 average homes.
1 1. Reduces the ATP’s “carbon footprint” for
purchased power by almost 9,000 tons of carbon
dioxide each year.
1 2. Project was awarded a $3 million, low interest
construction loan with $1.2 million principle
forgiveness from the Virginia Clean Water Revolving
Loan.
1 3. CHP supports HRSD’s 2020 Vision and Strategic
Plan environmental objectives for alternative energy,
energy efficiency, and conservation and recycling.
HRSD Atlantic Treatment Plant (ATP)
Combined Heat and Power System
Background
The Hampton Roads Sanitation District (HRSD) recently completed an upgrade to the Atlantic Treatment
Plant (ATP), where the plant capacity was increased from 36 million-gallons per day (MGD) to 54 MGD.
As part of the expansion, the solids digestion processes were reconfigured which resulted in excess
digested gas production. As part of HRSD’s mission to become more sustainable, HRSD evaluated
alternatives for the increased use of digester gas and other potential renewable energy sources at the
ATP. HRSD decided to install a combined heat and power (CHP) system comprised of a gas cleaning
system and two engine generators for power production and heat recovery.
Challenge
The digested gas is very corrosive due to high concentrations of hydrogen sulfide (H2S) ranging
above 2,000 parts per million and siloxane concentrations at 30 mg/m3. As a result, the gas must be
cleaned prior to running the engine generators. Also, robust digester gas generators are necessary for
continuous and reliable operation for producing power. Since the CHP system parallels utility power, a
significant effort is required to integrate the CHP engine generators with the standby diesel generators.
Lastly, the heat recovery system provides another layer of complexity where the exhaust and jacket
water heat is recovered from the engine generators. This heat is then used for digester hot water boilers
and building heat.
Solution
Robinson Group’s gas treatment system was selected since the manufacturer had significant experience
with treating digester gas. In addition, a biological H2S removal system manufactured by Biogasclean
was selected to reduce the high levels of H2S concentrations, thus lowering the operational costs of
the gas treatment system. Two 1100 kW Cummins Engine Generators with a heat recovery system were
selected to produce nearly half of the plants power consumption and recover approximately 4 million
BTU/h of heat. Cummins engine generators were selected due to their robust design, HRSD’s thorough
experience with Cummins standby diesel generators and ease of system integration with the plant’s
existing Cummins diesel generators.