By Ray Dougherty
A Mississippi environmental contractor and oil recycler has refined its process into a national model for efficient aerobic biological treatment of petroleums-laden wastewater. Working in concert with the Environmental Protection Agency (EPA), the state and its local wastewater authority, the plant successfully cleans up millions of gallons of oily waters. Treated effluent meets compliance for discharge directly into a POTW (publicly-owned treatment works) sewer utility.
Waste Oil Collectors, Inc. (WOCI) of Gautier, MS, is a regional environmental contractor recycling oil and treating a wide variety of wastewaters along the industrial Gulf Coast.
Using its innovative methods of aerobic treatment and bioaugmentation, WOCI degrades petroleum hydrocarbons in its waste stream to near non-detectable levels, reducing COD levels to within discharge compliance limits. The operators of WOCI are now nationally recognized experts, sought after for consultancy by other petroleum wastewater treaters who share the unique challenges of balancing environmental and business considerations in a traditionally rough and dirty industry. They are all faced with increasingly stringent regulation and scrutiny.
WOCI continues to refine its methods to maximize treatment efficiencies. These include advancements in aeration and oxygenation, as well as a bioaugmentation system that through lab research — and experience in field applications — has identified the most beneficial strains of microbes, inoculated with the correct dosage and timing. WOCI has also embraced the latest high-tech respirometry research available, revealing new and exciting data about oxygen uptake — the rate of oxidation necessary to naturally degrade petroleums and other stubborn organics.
Know The Enemy
The outstanding treatment success — and compliance record — at WOCI begins with awareness and control of the types of waste accepted.
"We closely watch what we take in," plant operator John Cambre said. "Our upper limit for COD levels of inbound materials is 50,000 (ppm). The acceptable pH range for our plant input is 5 to 9."
Cambre said these levels are checked daily, on every batch of inbound product: "It's vital. Because of the wide range of source material we treat, we must remain sensitive to the contents."
About 80% of WOCI's treatment volume originates in some form from the marine industry across the Gulf Coast. WOCI collects and treats loads from Mobile to New Orleans, but "marine-related" can encompass everything from machine shops' oils and hydraulics, to storage tanks and oil rigs, to bilge waste and ship yards' contained runoff.
The total petroleum hydrocarbons (TPH) levels can vary significantly from load to load, necessitating strict monitoring of inbound volume and dictating treatment methods load-by-load, batch-by-batch. Those inbound loads can range from 70% to 80% water, to just 5% water in a single tank load, Cambre said.
The remaining 20% of WOCI's inbound volume comes from factory or maintenance shop sumps, tank washes, underground storage tanks and other "industrial-environmental" sources — even stormwater and contained runoffs. WOCI accepts no kitchen wastes (food grease) or septic (domestic waste), characterized as non-petroleum in nature.
"We could double our wastewater intake, without being so very selective," Cambre said.
Yet even with this rigid selectivity to inbound content, WOCI treated some 4.2 million gallons of wastewater in 2003, the facility's largest annual treatment volume to date.
WOCI operates its own fleet of seven tanker trucks for oil and wastewater collection and it accepts loads from other licensed contractors. When WOCI collects at client locations, pH levels are checked directly in the field before loading. If those levels are too acidic or caustic to meet WOCI's acceptance limits, the load is rejected for pickup and alternative treatment arrangements are explored. Contract haulers' tanker loads likewise are monitored when they arrive at WOCI's treatment plant, for pH levels as well as total COD.
Full Treatment
The treatment process at WOCI cleans oil, trace hydrocarbons and other organics including soaps. The plant meets EPA effluent limitations as required by 40 CFR, Parts 136 & 137. Ultimate discharge of WOCI's treated waters is directly to the local POTW, the Gulf Coast Regional Wastewater Authority. Environmental compliance is managed by Mississippi's Department of Environmental Quality (DEQ), which issues the plant's state permit. Analyticals from WOCI's extensive monitoring are provided to DEQ as part of the permit compliance.
Upon acceptance of oily wastewaters, the initial phases of treatment are gravity separation, along with heat and chemical treatment. Used oils are sold on the open market and are primarily used as boiler fuel. After primary separation, waters are diverted into one of ten 10,000 gallon aerobic treatment tanks for additional pH adjustment and bioaugmentation.
Typical treatment batches are conducted in only one of these tanks lasting three to five days. Ongoing aerobic biological treatment can last as long as 10 to 20 days for what Cambre characterizes as "aggressive waters". These batches routinely contain tougher-to-treat glycols, requiring longer periods of biological contact, prior to an additional treatment phase through bag filters (filtration to 5 microns).
Following pH adjustment, WOCI doses its biologicals. This bioaugmentation consists of introducing specialized microbes which possess natural metabolic pathways to degrade oil, grease, petroleum hydrocarbons, phenols, glycols and other organic contaminants. WOCI only uses Munox® microbial additives in its system.
The dosage combines 1,000 ppm of a petroleums-specific product series, with half that dosage amount of an additional Munox® series which targets and readily degrades phenols. This typical three- to five-day treatment process requires only a single dosage of those biologicals, which maintain their metabolism of wastes through closely monitored aeration.
"Besides these great bugs (microbes) we utilize, the key to our treatment is the aeration we employ," Cambre said. "We've refined our aerobic system through the years to where, today, we gain peak efficiencies in both oxygenation and treatment results. I could not total the hours we have spent tankside with our DO (dissolved oxygen) meters, tweaking our aeration systems."
In the case of aggressive wastewaters (treatments of more than five to seven days), WOCI may re-dose the biologicals, as well as a nitrate addition. In such cases, the "booster" dosage can be a concentrated Munox® Multiplier formulation, which oxidizes recalcitrants much more quickly.
The nitrate serves as a nutrient for the microbes. WOCI will use simple ammonia nitrate in a 1 to 3 ppm dosage. When nitrate levels drop below a couple parts per million in the system, the biological degradation of petroleums can slow or "stall", Cambre said.
Although optimized with proper nutrients in its liquid formulation, the Munox® microbes consume nitrogen in about a one to 10 ratio versus their metabolism of organic carbons.
Unlike domestic sewage, or a food processor's wastewater, WOCI's input is not overly nitrogeneous in nature. A total depletion of that nitrogen source in the treatment system will require replenishment, whereupon the microbes will again "take off" and complete their degradation of hydrocarbons to nearly undetectable levels.
Know Your Bugs
To gain further insight into the optimal timing and duration of its biological treatment processes, WOCI recently commissioned sophisticated respirometry analysis. The lab chosen for the study was RespirTek(SM) in nearby Biloxi, MS.
The data will assess organic loadings in the system (short-term BOD of two to 10 hours), determine fingerprints for waste degradation, and measure oxygen demand (optimum O2 uptake).
"Respirometry is a way of communication with microbial communities," said RespirTek President/CEO B.J. Hook. The technology measures the respiration of microorganisms. Media can vary from groundwater or soil, to a composting or sewage treatment system, to almost anything that contains or could contain living organisms. Changes in contaminant concentrations are directly related to changes in respiration during monitoring, and are the basis of respirometric results.
RespirTek conducted analysis based on samples taken from WOCI's actual treatment tanks at the plant, with the actual Munox® dosages used in treatment applications.
After slow and steady oxygen uptake over the initial 20 hours of contact (0.0 to 3.0 mg), RespirTek reported the microbes in the system exponentially increased their oxygen uptake over the next 40 hours (from 3 mg to 360 mg). The O2 uptake from that point continued more of a slow, steady climb, becoming endogenous at over 366 mg oxygen consumption at 72 hours. COD analyses starting and ending indicated a 53% drop in concentration over 40 hours.
"John Cambre and his team at WOCI have grasped the science behind their treatment methods," Hook said. "The more oxygen (aeration) provided to these microbes, the faster and more complete their metabolism (respiration) of contaminants. As an independent lab we were favorably impressed with the WOCI usage and degradation results of the Munox® product line in this study."
Three days (72 hours) was the total duration of data monitoring and recording for this study.
"After 3 days, (oxidation) activity decreases because that's generally all it takes to deplete the hydrocarbons present in that batch," Cambre said. "The data from this study definitely helped us with the timing of our treatment duration, and also with the timing of nitrate additions, if needed. The study data is very worthwhile, reinforcing our field experience.
"Recycling is the nature of our business. But we're not only recycling oils, we literally recycle water too. We feel our treatment methods are among the most efficient — and environmentally friendly — anywhere, for treatment of petroleums-laden waters. That equates to efficiencies for our customers, in lower costs than other treatment and disposal methods. We're also using far less energy, water and chemicals than many other traditional methods of treatment and filtration. We feel that's good for the environment, as well as good for business."
About the Author:
Ray Dougherty, is a bioremediation consultant with Industrial Environmental, of Sarasota, FL. He can be reached at 941-780-5023, or [email protected].
