Waste Water

 

Engine & Vehicle Cleaning Wash Water

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.

 

Floor Cleaning Wash Water

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.

 

Sump Sludge

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.

 

Problems

 

Environmental Impact

Wastewater ends up in one of three places.

  1. Storm Drains.  Water flows untreated from storm drains directly to creeks, streams, lakes, bays, and oceans.  If this water is contaminated, it can harm aquatic life; even soapy water can upset aquatic ecosystems.  
  2. Septic Systems.  Discharges to septic systems can cause soil, groundwater and drinking water contamination, creating site cleanup liabilities.
  3. Sanitary Sewers.  Metals accumulate in sewage treatment sludge, preventing its beneficial use.  Some contaminants “pass through” and are discharged to lakes, rivers, bays, and oceans.

 

Why be Concerned About Oil/Water Separators?

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?

 

Worker Safety

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.

 

Regulations

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.

 

Solutions

 

Waste Reduction

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.

 

To make sure your Oil/Water Separators works properly, remember:

·         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.

 

Heavier or Lighter Than Water?

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.

 

How do I Keep Oil and Solids Out? 

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.

 

Recycling
Use oil-only absorbents to separate and recycle oil from your OWS.

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.

 

Use microbes to digest oil in your OWS.

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.

 

Waste Management

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

 

Case Studies: 

 

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%.