Ronald D. Neufeld

Temperature, cyanide and phenolic nitrification inhibition

Abstract Laboratory evaluations were conducted of the rate of ammonia biooxidation to nitrite by an autotrophic culture of nitrifiers. Ammonia oxidation biokinetics were found to follow Michaelis-Menten-type relationships. Alterations in Michaelis-Menten kinetics were quantified with elevated temperatures and selected trace organics typical of steel industry type wastewaters. Based on data obtained, the toxic inhibition to biological nitrification decreased in the order of free cyanide, coal tar acid phenolics (derived from a coke plant), phenol, 2,3,6-trimethylphenol, 2-ethylpyridine, 2,4,6-trimethylphenol, complexed cyanides and thiocyanate. All substances except free cyanide appear to follow a “shoulder effect” where low levels of inhibitor had no influence on rates of biological nitrification while higher levels had profound effects. Upper temperature limits for stable optimum nitrification is about 30°C with decreasing rates of nitrification on either side of this optimum. Nitrification rates approach zero as temperatures of wastewater approach 45°C.

Phenol and free ammonia inhibition to Nitrosomonas activity

Abstract Laboratory evaluations were conducted of the rate of ammonia bio-oxidation to nitrite by an autotrophic culture of strict nitrifiers. Ammonia oxidation biokinetics was found to follow Michaelis-Menten type relationships. Experiments were conducted to quantify the influence of phenol, and the influence of un-ionized (free) ammonia on biokinetic parameters. Results show that the Michaelis-Menten constant varies with the square root of ambient phenol concentration, and that the influence of un-ionized ammonia on ammonia oxidation may be best described by a “substrate-inhibition” model which follows from classical Monod kinetics. This model explains, to a large degree, observed differences in ammonia bio-oxidation rates as functions of pH. Conclusions based on engineering calculations are presented to illustrate design and operational considerations for the biological removal of wastewater ammonia.

PAH partitioning mechanisms with activated sludge

Abstract Research was conducted to study the accumulation of polycyclic aromatic hydrocarbons (PAH) in biological sludge produced from an activated sludge process. For the purpose of modeling PAH distribution, the activated sludge process was viewed as a two phase chemical system in which PAH molecules partition between the wastewater and the lipid fraction of the biological sludge. PAH distribution between the two phases was quantitatively represented by an equilibrium distribution coefficient. An equation was developed from thermodynamic principals to estimate lipid-wastewater distribution coefficients for PAH. Solving this equation required the use of the UNIFAC method for calculating activity coefficients. PAH sludge sorption isotherms were experimentally determined for both a relatively clean “control” wastewater and a fixed bed coal gasification wastewater. Measured PAH distribution coefficients compared well to estimated distribution coefficients. The model indicates that PAH partitioning may be represented by an equilibrium distribution coefficient which relates the solubility of the PAH in the sludge lipid fraction to the solubility of PAH in the wastewater.

Sedimentation basin performance at highway construction sites

Sedimentation basins (SBs) are commonly used during highway construction for erosion and sedimentation pollution control as well as for attenuation of overland storm waters. In order to evaluate the sediment removal capacity of these SBs, four basins were selected for monitoring from a new highway construction that extends I-99 to I-80, in Pennsylvania. Between September 2004 and August 2005, ten sampling trips were conducted during which basin inlet and outlet water samples were obtained. The SB samples were analyzed for pH, color, turbidity, total suspended solids (TSS), volatile suspended solids (VSS), total and dissolved iron, magnesium, manganese, aluminum, calcium, sulfate and phosphate. The data showed peaks in concentrations of TSS, total aluminum, total manganese, total iron and total phosphate that closely correlated to localized rainfall peaks. For certain samples, the concentration of TSS in the outlet was higher than the TSS concentration at the basin inlet, suggesting sediment re-suspension. In general SBs managed high flows during wet weather events, but were not effective in capturing particulates. This paper discusses the need for Best Management Practices (BMPs) for the design of SBs that reflect contemporary concerns for management of particle removal and to control the release of particulate-bound metals. This paper also evaluates the water quality impacts of naturally occurring acidic drainages into SBs, as several acidic seeps with pH in the range of 5-6 and having high dissolved concentrations of metals (Fe, Mn, Mg and Ca), sulfate and phosphate were observed draining into the SBs.

Stabilization of Heavy Metal Containing Hazardous Wastes with Byproducts from Advanced Clean Coal Technology Systems

The purpose of this investigation was to evaluate the success of residues from advanced Clean Coal Technology (CCT) systems as stabilization agents for heavy metal containing hazardous wastes. In the context examined here, stabilization refers to techniques that reduce the toxicity of a waste by converting the hazardous constituents to a less soluble, mobile, or toxic form.1 Three advanced CCT byproducts were used: coal waste-fired circulating fluidized bed combustor residue, pressurized fluidized bed combustor residue, and spray drier residue. Seven metal-laden hazardous wastes were treated: three contaminated soils, two air pollution control dusts, wastewater treatment plant sludge, and sandblast waste. Each of the seven hazardous wastes was treated with each of the three CCT byproducts at dosages of 10, 30, and 50% by weight (byproduct:waste). The treatment effectiveness of each mixture was evaluated by the Toxicity Characteristic Leaching Procedure. Of the 63 mixtures evaluated, 21 produced non-hazardous residues. Treatment effectiveness can likely be attributed to mechanisms such as precipitation and encapsulation due to the formation of hydrated calcium silicates and calcium sulfo-alu-minates. Results indicate that these residues have potential beneficial uses to the hazardous waste treatment community, possibly substituting for costly treatment chemicals.

Kinetics of chemoheterotrophic microbially mediated reduction of ferric EDTA and the nitrosyl adduct of ferrous EDTA for the treatment and regeneration of spent nitric oxide scrubber liquor.

Biomass from a prototype reactor was used to investigate the kinetics of chemoheterotrophic reduction of solutions of ferric ethylenediaminetetraacetic acid (EDTA) and solutions containing the nitrosyl adduct of ferrous EDTA using ethanol as the primary electron donor and carbon source. A series of batch experiments were conducted using biomass extracted from the scrubber solution treatment and regeneration stage of a prototype iron EDTA-based unit process for the absorption of nitric oxide with subsequent biological treatment. Using a linear-sweep voltammetric method for analysis of the ferric EDTA concentration, iron-reducing bacteria were found to behave according to the Monod kinetic model, at initial concentrations up to 2.16 g chemical oxygen demand (COD) as ethanol per liter, with a half-velocity constant of 0.532 g COD as ethanol/L and a maximum specific utilization rate of 0.127 mol/L of ferric ethylenediamine-tetraacetic acid [Fe(III)EDTA]*(g volatile suspended solids [VSS]/L)d(-1). Based on batch analyses, biomass yield and endogenous decay values of iron-reducing bacteria were estimated to be 0.055 g VSS/g COD and 0.017 L/d, respectively. An average of 1.64 times the theoretical (stoichiometric) demand of ethanol was used to complete reduction reactions. Kinetics of the reduction of the nitrosyl adduct of ferrous EDTA are summarized by the following kinetic constants: half-velocity constant (Ks) of 0.39 g COD/L, maximum specific utilization rate (k) of 0.2 mol/L [NO x Fe(II)EDTA(2-)](g VSS/L)d(-1), and inhibition constant (K(I)) of 0.33 g COD/L, as applied to the modified Monod kinetic expression described herein. Based on batch analyses, the biomass yield of nitrosyl-adduct-reducing bacteria was estimated to be 0.259 g VSS/g COD, endogenous decay was experimentally determined to be 0.0569 L/d, and an average of 1.26 times the stoichiometric demand of ethanol was used to complete reduction reactions.