What is "Inflow" & "Infiltration" or I/I

For over 20 years, Rowland, Inc. has been effectively assisting Florida municipalities correct their infiltration issues as the state's leading applicator of the structural, cementitious product, SewperCoat®.  Now, with our newest product, InflowShield®, we are able to dramatically reduce inflow.  Combating sewer system infiltration and inflow (I/I) has become our company mission.

Inflow is stormwater entering the sewer system, such as through improper connections, manhole lids and chimneys and missing cleanout covers, to name a few; generally water entering from above ground.

Infiltration is groundwater entering the sewer system via cracks/leaks in pipes, mains, laterals and manhole and wet well walls; generally entering from below ground.

Why consider an Inflow and infiltration (I/I) abatement project?

There are many direct environmental considerations when looking at your I/I problems.  Where you have infiltration, you most likely have exfiltration, meaning that the ground and possibly ground water surrounding the leaking infrastructure can become contaminated.  Additionally, living in a state where we rely on healthy aquifer water, we need to recognize that when ground and storm water are diverted to our wastewater plants they cannot filter down to and replenish our drinking water source.  Another very serious environmental concern is sanitary sewer overflows (SSOs).  SSOs occur most frequently in systems that are overburdened with storm and groundwater I/I, and are a source of contamination, consent orders, fines and public scorn.

What does I/I cost?

The cost is tremendous.  Just in real dollars, all flow must be processed, and conservative estimates place treatment cost at $1-$3 per gallon. If you consider that as much as 12,000 gallons or more, PER DAY, can enter the system during a severe storm event IN ONE MANHOLE, the numbers become daunting.

Add to direct treatment cost, the indirect costs, such as reduced lifespan of the system pumps and other equipment, SSO cleanup, litigation and liability costs, reduced system capacity, meaning a moratorium on future expansion, and potentially lower housing values. 

What causes corrosion in our sewer system?

Deterioration of the interior of manholes and wet wells is caused by the microbial induced corrosion process (MIC).  First, H2S builds in areas of laminar flow (inside the collection system mains), it is then ejected into the manholes or wet wells, the ejection rate increases in turbulent flow, the H2S gas then dissolves into moisture on the structure’s surface, oxidation then creates elemental sulfur, which is a food source for the bacteria in the sewage.  Sulfuric acid is the byproduct of the digestion process of the bacteria.  It is the sulfuric acid that is corrosive, not the H2S gas itself!

What to do? Rehab or replace?

It is far more cost effective to implement a pro-active rehab approach rather than a re-active replacement approach.  In fact, to replace a six foot deep manhole, taking it off-line, repairing the road and other infrastructure, can cost $10,000-$20,000/ea or more, but to rehabilitate that same size structure with a structural,  100% pure fused calcium aluminate solution can cost as little as $1,000-$2,000/ea.

Rehabilitation products offered by Rowland

Rowland, Inc. has been a statewide leading applicator of 100% pure fused calcium aluminate since 1992.  To date, we have rehabilitated over 145,000 vertical feet of manholes, nearly 27.5 miles!  Currently we offer customers two choices of 100% pure fused calcium aluminate, SewperCoat® and Strong HP®.  We also offer a calcium aluminate blend, Strong MS.  In addition to our structural, cementitious manhole and wet well rehabilitation, we also now offer InflowShield®, a stainless steel inflow dish inserted onto the rim of the manhole, under the lid.  The InflowShield® captures inflow and fills to capacity, preventing additional stormwater, sand, grit and foreign objects from entering the collection system. During a severe storm event, up to 12,000 gallons of storm water can enter a single manhole in one day.  And, being constructed of stainless steel, InflowShield® can be used with confidence throughout a system without fear that the dish will fall into the manhole due to fracturing and wear around the rim, which is a common concern with plastic dishes.

100% pure fused calcium aluminate VS blended calcium aluminate products

Only 100% pure fused calcium aluminate (CA) can offer full, long term protection in a sewer environment.  When a 100% pure fused calcium aluminate product was compared to blends in the independent Hamburg study, the 100% CA had only a .003% surface loss after a year in highly aggressive wastewater chamber, and the blend had a 10% surface loss.  The main difference between 100% CA and blended CA is the neutralization capacity of 100% CA. In 100% CA products, like SewperCoat® , hydrogen ions are consumed by the alumina gel, resulting in a raised PH, therefore a reduction in corrosion and abrasion.  “CA mortars were shown to resist MIC significantly better than portland and blended portland cement mortars.  Pure 100% CA exhibited the best performance”
That being said, 100% pure fused calcium aluminate products are, initially, more costly than blends, but if long term costs are considered, 100% CA becomes more cost effective.  We suggest that blends may have a place in some gravity systems where the acid numbers and structural integrity indicate extremely low levels of corrosion. Blends can be structural and economical, but only offer short term acid neutralization, as compared to 100% CA.