Sculpting Wastewater Treatment
A clay-based technology molded for small quantity wastewater generators
- By Richard Brown
- Sep 01, 2002
Virtually all industrial activities generate some amount of wastewater. Disposal of this water in an environmentally responsible way has been a legal requirement since the passage of the Clean Water Act in 1972. The initial targets of the U.S. Environmental Protection Agency (EPA) for enforcing this and other water laws were the large sources of water pollution, namely the corporations with big manufacturing facilities that generate large volumes of industrial wastewater. These "large quantity" generators are now mainly in compliance. As a result, EPA's focus has turned to "small quantity" wastewater generators.
Despite the length of time that water pollution laws have been in force, many, and perhaps most, small quantity generators still don't fully understand that these laws also pertain to them. As a result, small quantity generators have become one of the principal sources of water pollution in the United States today. Examples of a few of the many types of small quantity wastewater generators include:
- Metal Working Plants
- Metal Finishing Plants
- Metal Plating Plants
- Die casting Plants
- Plumbing Supplies Mfg.
- Power Transformer Mfg.
- Battery Manufacturers
- Wastewater Haulers
- Trucking Companies
- U.S. Military
- Auto Part Remanufacturers
- Radiator Repair Companies
- Tire Manufacturers
- Car and Truck Washes
- Aircraft Manufacturers
- Animal Feedlots
- Furniture Manufacturers
- Cutlery Manufacturers
- Oil Re-refiners
- Paint Manufacturers
- Painting Companies
- Printing Companies
- Glass Washing, Grinding and Polishing Companies
- Textile Manufacturers
- Cloth Dying Companies
- Liquor Distilleries
- Sugar Processors
- Citrus Growers / Processors
- Meat & Poultry Processors
For the purpose of this discussion, large quantity generators may be characterized as producing wastewater volumes over 100,000 gallons/day, using conventional, fixed, multi-step treatment systems, having a high degree of technological sophistication and relatively high budgets for wastewater treatment. In contrast, small quantity generators are characterized by much smaller wastewater volumes, little or no existing infrastructure for wastewater treatment and little space in which to put a treatment facility, very little knowledge of wastewater treatment and a minimal or nonexistent wastewater treatment budget. This combination of factors makes it extremely difficult and expensive for most small quantity generators to be able to come into regulatory compliance.
A Sodium Bentonite Solution
A simple, easy-to-use, cost effective, clay-based technology has been developed to provide a solution for the dilemma faced by small quantity generators. In contrast to the large, expensive, multi-step, space intensive and often technically challenging treatment systems typically used by the large quantity generators, this technology can be used by minimally trained personnel and can work in most applications in one step in a single tank.
This is due to the large surface area and high ionic exchange capacity of sodium bentonite clay used in this technology. The bentonite provides a substrate for attracting and binding dissolved contaminants in industrially generated wastewater. Additionally, the broad, sheet-like clay particles in sodium bentonite can be aggregated together to form tight "floc" structures that will capture and remove suspended contaminants in wastewater. When combined with appropriate pH control agents, emulsion breakers, oxidizers, selective coagulants and selective flocculants, the sodium bentonite removes both dissolved and suspended contaminants, encapsulating them in a sturdy clay floc structure that rapidly settles to the bottom of the treatment tank.
"One-size-fits-all" approaches don't work for industrial wastewater treatment because each wastewater stream is chemically unique. For this reason, different formulations of clay-based products have been developed to target different types of wastewater. These are available in both powder and granular forms to fit different types of use requirements.
In a typical application, wastewater is pumped into a mixing tank and mixed with the clay-based product using a low speed, high turbulence paddle mixer. The amount of clay-based product required is usually about 0.5 percent to 1.5 percent of the weight of the water to be treated. After the required amount of product for the particular application has been added, the mixing is continued until substantial clay flocs are formed. This normally takes from 3 minutes to 5 minutes. The mixer is then turned off to allow the flocs containing the trapped contaminants to settle to the bottom of the tank. This takes from 1 minute to 3 minutes depending on the depth of the mixing tank and will result in a layer of clay flocs on the bottom of the tank with clear water on top. Clear water may then be drained from the tank and sewered or reused as process water. Sludge, which contains about 70 percent to 90 percent water, can then be drained from the tank and processed to further dry it in preparation for disposal. The entire treatment process typically takes less than 10 minutes per batch. Sludge produced by this process may be easily dehydrated for disposal air drying, using filter belts or filter presses, or by thermal drying depending on the rate and volume of sludge generation. The dried sludge typically will pass TCLP test criteria for solid waste disposal so it can be taken to a municipal landfill for cost effective disposal.
Using this technology, very small quantity generators can actually process their wastewater in a 55-gallon barrel fitted with a small mixer. For generators of larger volumes of wastewater, a wide variety of more sophisticated processing equipment is also available that will automatically fill the mixing tank with water, add and mix the product, drain the cleared water and filter the sludge. The equipment can be sized to fit the volume requirements of any application.
Simplicity of use, speed of processing and assurance of the ability to properly dispose of process water and sludge in an environmentally sound manner makes the use of clay-based wastewater treatment technology an extremely cost effective choice for small quantity industrial wastewater generators.
Case Study: Glass Grinding Wastewater
A wastewater treatment system made by Hydro-Tech Environmental Systems Inc. (HTES) was installed in June 1993 at the largest supplier of specialized glass products for the U.S. Department of Defense (DOD), the National Aeronautics and Space Administration (NASA) and the telecommunications industry. The HTES Water REATM system uses Wyo-Ben Inc.'s Cleartreat® 2000 Reactant product line for clarification, separation and encapsulation of the contaminants. Economics of installing the system and using the Reactant pointed to a capital cost return of 11 months.
Prior to choosing this solution, the manufacturer was having their wastewater from this process hauled. The cost was $.50 per gallon. At that time, their requirements for hauling were minimal due to the small volume of water being created from the process. However, the process being used was due to quadruple that year, making hauling prohibitively expensive. A committee was formed to evaluate available technologies. Three were found to be capable of treating the waste stream--a membrane system, a traditional polymer system and the HTES Water REATM system.
After trial runs, the HTES system was found to be the most reliable, forgiving of changes in the waste stream, requiring the least maintenance and operational time by personnel, produced a non-hazardous sludge and was the most cost effective. All cost estimates were obtained by the client while evaluating the different technologies. The HTES treatment cost per gallon is representative of today's newer system and programmable logic control (PLC) technology.
Wastewater enters the treatment system from five different sumps into equilibration tank #1. Acid is added into this tank to drop the pH to the preset level entered into the PLC via the touchscreen. When this pH level has been attained and the level of wastewater in the tank is correct (the conditions are entered into the PLC via a touchscreen) then the wastewater is transferred to equilibration tank #2 for "fine tuning" of the pH. The pH level and tank level for transfer to the HTES Water REATM; are also entered into the MMI (Man-Machine Interface). In addition, alarm parameters for pH and tank levels are entered into the MMI.
Once this pH level has been attained and the level of wastewater in the tank is correct, wastewater is transferred to the HTES Water REATM; Processor for final separation. It is in the processor that the Wyo-Ben Cleartreat® 2000 Reactant is added. The processor has four mix tanks, a reactant feeder, a filter bed, and a recovery tank to store the processed water. In addition, there is a bulk reactant feeder that holds 2210 pounds of reactant. The bulk reactant feeder provides reactant to the processor. All control and alarm parameters and motor speeds are entered into the system via the MMI display / touchscreen.
The introduction of this technology made it possible for the client to double their production output while reducing labor costs, down time and quantity of consumables used. With the recycling of their sludge into construction materials, they have also eliminated their "cradle to grave liability". Additionally, they were able to comply with their international corporate-wide waste reduction program by having the sludge used in a sustainable process that reduces the use of landfills and the consumption of natural resources for construction materials.
In 2000, after the client's company was purchased by an international telecommunications firm, the volume of the waste stream increased three-fold while the concentration of one of the contaminants went up ten-fold.
After researching available technologies and their associated costs, the client again chose the HTES system using Wyo-Ben's Cleartreat® 2000 Reactant for treatment of their wastewater.
This article originally appeared in the 09/01/2002 issue of Environmental Protection.
Richard K. Brown is vice president, resources of Wyo-Ben Inc.,Billings, Mont. He has more than 24 years of experience developing clay-based products for environmental applications including wastewater treatment.