Many shops wash engine compartments or entire vehicles as part of their business. The runoff from engine compartment washing often contains oil and grease that are a threat to aquatic life and drinking water supplies. The detergents used in both types of washing can also be a threat to aquatic life and drinking water supplies. If washing is done outside without the proper containment and sewer hookup, the wash water eventually reaches a storm drain or septic drain field. Water from engine and vehicle washing is process wastewater, and should never be allowed to flow into storm drains or septic drain fields.
The
runoff from shop floor washing often contains metals, oil, and grease that are a
threat to aquatic life and drinking water supplies. It is for this reason that
many local governments require that wash water be routed to a sanitary sewer for
treatment in the local waterworks, rather than allowing it to run into storm
sewers which ultimately drain into creeks, streams, and lakes. In addition, many
local governments require that shop floor drains be routed to a passive
oil/water separator before being discharged to the sanitary sewer. The sludge
that gathers at the bottom of such separators may be a hazardous waste; testing
is required to establish the nature of the sludge. Some shops reduce the amount
of sludge that collects by utilizing an active oil/water separation system to
skim oily wastes. The concentrated oily waste is retained by the system and
collected periodically for recycling.
The sludge that gathers in your sump or oil/water separator can be a
hazardous waste. You will need to have the sludge tested by a laboratory to
determine if it is hazardous.
Wastewater ends up in one of three places.
Oil/water separators (OWS) can be costly to maintain, and if not properly
managed, can pollute surface and ground water, and lead to costly violations.
Have you taken steps to minimize the effects of your OWS on your budget and the
environment?
Unless the material being cleaned up has toxic properties, there is little concern to workers doing the clean up. Risk of slipping always exists with wet floors so OSHA requires clearly marking the wet areas.
The Clean Water Act makes it illegal to
discharge pollutants to surface waters; violators can face imprisonment and
fines of up to $25,000 per day! Storm drain connections to indoor drains or
sinks are prohibited in most areas. Storm
drains are usually located outside a shop.
If you are unsure about the nature of your shop drains, ask the building
manager or local sewer authority whether any of the drains are connected to
storm water sewers.
Keep a dry shop.
The history of wastewater regulations is clear:
discharge limits will continue to become more stringent.
Minimize the impact of these regulations on your shop by adopting a dry
shop goal. A dry shop is a shop
that has sealed all of its floor drains. Although
a 100% “dry shop” may not be feasible in your area due to melting snow and
ice, the methods and equipment presented in this fact sheet will help you reduce
floor wash water volume and contamination.
This, in turn, reduces your liabilities, protects the environment and
community, and even saves you time and money spent cleaning floors.
The
least expensive approach to dealing with floor wash water is to avoid producing
it if at all possible. Leak prevention practices such as using drip pans to
prevent fluid leaks from reaching the floor and using funnels to avoid spillage
can help minimize the need to wash down oily spots. Dry cleaning methods such as
using a push broom and dustpan to get up debris and dust also help avoid the
need to wash the shop floor.
·
Eliminate contaminants:
Don't rely on the OWS to handle wash water from fuel, coolant, solvent, oil, or
paint spills. Instead, clean up spills when and where they occur with dry
methods (see the Floor Cleanup fact sheet).
·
Wash without detergents:
Emulsifying cleaning compounds disperse oil in wash water and make OWSs
ineffective—oil passes right through to the sewer. High-pressure water or
non-emulsifying cleaners are sufficient for most cleaning applications.
·
Minimize loading:
Minimize the amount of solids and oils that enter your OWS. The less solids and
oils that reach the OWS, the less frequently sludge and floating oil must be
removed from the OWS and the better it will work. Also, minimize the amount of
wash water reaching the OWS. Excessive water flow can flood an OWS, forcing
wastewater through it too fast to allow separation; the result: oil and other
contaminants pass right through to the sewer. OWSs should not be used to treat
storm water runoff.
OWSs treat vehicle and floor wash water by allowing substances lighter than water to float and substances heavier than water to sink. Many OWSs also have baffles, coalescers, and oil skimmers to speed-up or enhance separation of these substances.
Filter, filter, filter. The best way to reduce OWS sludge is to keep solids out of vehicle and floor wash water. Install progressively finer grates and screens over the drains to the OWS inlet in order to maximize solids separation:
· Begin with steel bars spaced 3/4 to 1-inch apart at the OWS drain inlet
· Add sequentially finer grates and screens (3/4 and 1/4-inch screens or 1/4-inch expanded steel mesh)
· Finish with reusable absorbent material to remove very small particles.
In some older OWSs, it is not easy to collect and remove separated oil.
If your OWS does not have an oil trough or other oil collection device,
you can use reusable absorbent pads that absorb only oil and grease. Put these
pads on the water surface to collect floating oil. Once saturated, squeeze the
oil from the pads; this oil can then be managed with your used oil, if the
squeezed oil is not contaminated with hazardous waste (get data on your wash
water quality or analyze a sample at least yearly to verify). The squeezed
absorbent pads can be reused.
Bioremediation is a proven technique to minimize the oil content in OWS
effluent and sludge and to reduce OWS cleanout frequency. Microbes added to an
OWS break down petroleum products suspended or dissolved in the wastewater,
floating oil, or sludge. Facilities using bioremediation have eliminated
wastewater violations and have reported reducing their sludge petroleum content
by more than 80 percent. Such reductions can lower the regulatory status of OWS
sludge, which will affect the required disposal method and disposal costs.
Bioremediation is typically performed under a vendor service contract. Microbes
are added to an OWS or interceptor lines on a regular basis to replenish microbe
populations. Microbes are nontoxic
and completely safe; the main by-products of bioremediation are water and carbon
dioxide. Vendor service contracts
usually cover all materials and labor; monthly costs range from $75 to $130,
depending on the size and contaminant loading of the OWS.
Using simple methods can minimize engine and vehicle cleaning wastewater.
Attaching spring-loaded nozzles to hoses used for washing will prevent the hoses
from being left running when not in use. High-pressure spray units can also be
used; they use about half as much water as a garden hose and provide better
cleaning. Wash water should be disposed of in a municipal sewer system. If a
facility is not connected to a sewer system, wash water can be collected and
recycled. Water recycling systems are becoming more popular; facilities ranging
from small self-serve carwashes to large fleet operations have installed
recycling systems.
DO
DO NOT
Car Repair and Car Wash
Bioremediation Benefits:
Limitations of Bioremediation:
Salem Boys Auto of Tempe, Arizona used sloping pavement, grates, and
screens to minimize OWS loading. These
controls, together with bioremediation, decreased the sludge cleanout frequency
and cost by 75%.
U.S. Postal Service Fleet Maintenance Facility, Huntington Beach,
California facility used bioremediation to reduce OWS effluent hydrocarbon
concentration by more than 80%.