Changing the rules in the middle of the game: Philadelphia's green infrastructure

Changing the rules in the middle of the game: Philadelphia's green infrastructure

Category: Water
Posted on: January 18, 2012 4:14 PM, by
 Liz Borkowski

Philadelphia and Green Infrastructure

Aging US water infrastructure has meant more leaks, flooded basements, and massive sinkholes in cities across the US. Fixing the water and sewer systems in need of repair will take billions of dollars, and it's hard to find that kind of money in the budget these days.

 

Saqib Rahim reports for ClimateWire on Philadelphia's decision to use "green infrastructure" rather than building a larger pipe system to handle the water that's dumped on the city during severe storms. The combination of more intense storms and more paved area is a problem: Impervious surfaces like roads, sidewalks, and parking lots can't absorb rainfall, so it ends up in the city's stormwater collection system -- which, in many older cities, is combined with the sewage system. When these combined systems are overwhelmed by heavy rainfall, the result is often that a rainfall-and-sewage mixture gets discharged into a local waterway. (Read more about this problem here.) Rahim explains Philadelphia's solution to this problem:

Instead of building an even larger pipe system to address the issue, [Water Department Commissioner Howard] Neukrug pitched the most aggressive "green infrastructure" plan in the country. Through increased vegetation, rain barrels, sponge-like roads and other measures, the city would try to absorb more water where it fell. The ground would filter out pollutants, reduce strain on the pipelines and make the city a more attractive place.

Neukrug tells Rahim that the green infrastructure solution will cost Philadelphia $2 billion, compared to $8 billion to $10 billion for larger underground tunnels. But the part of the city's plan that's currently causing a controversy is what water customers will pay. They'll now be charged not just for the water they use, but for their contributions to stormwater problems -- that is, sites with a lot of impervious surfaces will pay more.

The average household will see an average bill rise from approximately $60 to around $63.50, Rahim reports. For some large businesses, though, costs could rise significantly over the next few years -- and 100 of these businesses have hired a lobbyist and met with the Water Department to oppose implementation of the new billing practices.

I can understand why these businesses are upset. When they invest and plan for their businesses' futures, they assume the rules will stay the same. Their extensive impervious surfaces are causing problems for public health, but they might not have realized that their decisions about what to pave were raising costs for the city's residents (and everyone else affected when its sewage ended up in local waterways).

Changing the rules isn't ideal, but it's the best solution if the current rules create incentives for behavior that harms public health. If this country had never changed the rules to make businesses start bearing more of the cost for problems they cause the general public (externalities, in economic language), we'd still have rivers so polluted that they catch fire. Governments can ease the pain by providing grants or low-interest loans to help businesses and individuals invest in greener setups -- and, Rahim reports, Philadelphia is offering loans to businesses that want to green their facilities. Increases in bills will also be capped at 10% or $100 per month.

Such an approach could also be used to address other public health issues like CO2 emissions -- but so far, opposition to a carbon tax has been stronger than support. In the meantime, I'll be watching Philadelphia's effort and hoping it succeeds with a green solution to water infrastructure challenges.

Source:  http://scienceblogs.com/thepumphandle/2012/01/changing_the_rules_in_the_midd.php#more

Example SWMM 5 Model for Activated Sludge

Note:   Example SWMM 5 Model for Activated Sludge

Here is one example of how to model an activated sludge tank.  The image is Wikipedia (http://en.wikipedia.org/wiki/Activated_sludge)  and is the watermark background in the SWMM 5 GUI.  There is 100 lps inflow, 20 percent recycle and 10 percent sludge drawoff.   You can adjust the amount of recycle and sludge altering the pump type 2 flows or if you want to increase the inflows – add more flow in the RawWater inflow node.

Three Flow Divider Link Example in SWMM 5

Subject:  Three Flow Divider Link Example in SWMM 5

You can have more than 2 downstream OUTLET Type links in the SWMM 5 dynamic wave solution.  Each link, Under5, Over5 and ReturnFlow is an OUTLET Link with a rating curve depth/flow table.  Depending on the depth in the storage node DIVIDER, the flow is computed from the table for links Under5, Over5 and ReturnFlow.

Output Statstics Manager to find negative flows in InfoSWMM

Subject:  Output Statstics Manager to find negative flows in InfoSWMM

Output Statstics Manager to find negative flows with these parameters:

1.       Pipe Features

2.       Use a Domain with your force mains

3.       Select Flow

4.       Event Dependent

5.       Total – NOT Mean or Peak to  find the negative and positive flows

6.       Large NEGATIVE Flow Threshold

7.       Large NEGATIVE Volume Threshold

8.       Zero for Interevent Time to pick up all values

9.       You will get a table that shows you the minimun flows, and a histogram of the flows

 

 

Flow Dividers in SWMM 5 Dynamic Routing

Note:  Flow Dividers in SWMM 5 Dynamic Routing

You can  have flow dividers in SWMM 5 dynamic routing by using Storage Nodes for the dividers, OUTLET links for the downstream links and minimizing downstream HGL effects. The needed components are:

1.   A Storage Node for the divider node as a OUTLET Link does not have a Surface Area,

2.   Two or More OUTLET Links as the downstream diversion and cutoff links,

3.   Two or More Rating Curves to divide the flow up based on either depth or head,

4.   Pumps, Outfalls or Steep Sloped Links Downstream of the diversion and cutoff links to minimize downstream HGL  effects