Timothy G. Ellis

Activated Sludge and other Aerobic Suspended Culture Processes.

This is a literature review for the year 2014 and contains information specifically associated with suspended growth processes including activated sludge and sequencing batch reactors. This review is a subsection of the treatment systems section of the annual literature review. The review encompasses modeling and kinetics, nutrient removal, system design and operation. Compared to past reviews, many topics show increase in activity in 2014. These include, nitrogen and phosphorus control, fate and effect of xenobiotics, industrial wastes treatment, and some new method for the determination of activated sludge. These topics are referred to the degradation of constituents in activated sludge. Other sections include population dynamics, process microbiology of activated sludge, modeling and kinetics. Many of the subsections in the industrial wastes: converting sewage sludge into fuel gases, thermos-alkali hydrolysis of Waste Activated Sludge (WAS), sludge used as H2 S adsorbents were also mentioned in this review.

The mechanism of hydrogen sulfide adsorption on fine rubber particle media (FRPM).

A commercial rubber waste product, fine rubber particle media (FRPM), was found to adsorb hydrogen sulfide (H₂S) at 0.12 mg H₂S/g FRPM of adsorption capacity. Since FRPM seems to be an attractive alternative to treat H₂S owing to its economic advantages as well as its physicochemical characteristics, several analyses were conducted to investigate fundamental information, surface properties, and breakthrough characteristics of FRPM as adsorbent. The physical properties of FRPM including composition and surface chemistry were investigated to compare its performance with commonly available commercial H₂S adsorbents such as activated carbon and assess the possible adsorption mechanism. The specific surface area of FRPM was less than 1% of activated carbon. FRPM does not have enough surface area supporting a pure physical adsorption of H₂S because it is particulate in nature with limited porosity. The adsorption of FRPM to remove H₂S was complex mechanism and involved a combination of zinc compounds and carbon black.

Experimental validation of the static granular bed reactor for industrial waste anaerobic treatment.

The static granular bed reactor (SGBR) is a unique high-rate anaerobic reactor designed to operate in a simple downflow manner, offering high chemical oxygen demand (COD) removal efficiencies (greater than 90%) resulting from high biomass retention in the system. A study was performed to evaluate the SGBR versus a control system, the upflow anaerobic sludge blanket (UASB) reactor, and to evaluate performance idiosyncrasies of the SGBR and the control. The two reactors were operated at three different hydraulic retention times (HRTs): 8, 16, and 24 h. The reactors treated synthetic wastewater, intended to simulate food industry waste, composed of sucrose and nonfat dry milk. Overall, COD removal was higher for the SGBR than for the UASB reactor. In particular, at a HRT of 8 h, the SGBR achieved a COD removal of 90.7% and the UASB reactor reduced the COD concentration by 77.5%. The UASB reactor’s specific COD loading factor proved rate limiting with values ranging from 0.19 to 0.94 gCOD/ ( gVS⋅d ) versus 0....

Septic wastewater treatment using recycled rubber particles as biofiltration media

Performance of the laboratory-scale recycled rubber particles (RRP) biofilter was compared to a conventional gravel system and a peat biofilter for treatment of septic tank effluent. During the study, the RRP biofilter provided similar or better performance than other systems in terms of organic removal and hydraulic capacity. After the start-up period, RRP biofilter achieved removal efficiencies for BOD5, total suspended solids (TSS), ammonia nitrogen of 96%, 93%, and 90%, respectively, over the range of hydraulic loading rates of 57–204 L/m2/d. On the other hand, the peat biofilter failed hydraulically and the gravel system showed high TSS concentrations in the effluent. RRP provided high surface area and sufficient time for biological treatment. In addition, RRP was observed to provide ammonia adsorption capacity. The results showed that RRP has the potential to be used as substitutes for natural aggregate such as gravel in septic system drainfields. The RRP biofilter can be used as alternative septic systems for the sites where an existing septic system has failed or site conditions, such as high groundwater table or small lot size, are not suitable for the installation of conventional septic systems.

Oxygen leakage during respirometric measurements: A caution on the use of PTFE tape

Abstract Oxygen leakage occurred during studies using respirometers that were supposed to be sealed. The leakage occurred around rubber stoppers inserted through the wall of the respirometric vessel and was caused by PTFE tape that was wrapped around the stoppers. Rewrapping the stoppers so that the tape did not extend between the stopper and the glass of the vessel eliminated the problem.

Research Digest: Field Validation of Biokinetic Coefficients for Predicting Degradation of Organic Compounds

This research was the first significant demonstration of an extant respirometric test to determine the biodegradation rate parameters (biokinetics) of select individual organic compounds at full scale wastewater treatment plants. Extant kinetics were measured at five different municipal and industrial activated sludge systems. The respirograms were well correlated with actual analytical measurements of compound disappearance for ethylene glycol and acetone. Furfural respirograms revealed differential rates of oxygen consumption, indicative of the formation of an intermediate compound which was identified as furoic acid in subsequent analysis. A calibration procedure was developed to assess the competent biomass concentration, since the COD fraction tended to underestimate the degrading fraction for two of the four test compounds. Acetone, for instance, had a measured influent COD fraction of 0.08%, and the actual competent fraction was estimated to be 2.3% based on the model calibration. Once the competent biomass concentration was determined, extant kinetic parameters were subsequently used to predict activated sludge system performance. Predicted effluent concentrations were within 2, 5, and 16% of the average measured concentrations for acetone, linear alkyl benzene sulfonate, and furfural, respectively. Day to day predictions for these compounds were less accurate, possibly due to the non-steady state nature of the activated sludge systems studied. Alkyl sulfate (AS) was not predicted well with respect to the percentage difference between predicted and measured concentrations. However, the overall mass difference was small (4.2 μgCOD/L predicted versus 0.82 μgCOD/L measured). The sub part per billion measured concentrations for AS were at least a magnitude of order lower than any of the other target compound concentrations. One of the surprising findings of the study was that the variability in kinetic parameter values was no more than typically observed in laboratory activated sludge reactors operated at steady-state. The dynamic operating nature and varying influent concentrations resulted in the maximum standard deviations for furfural at the Cedar Rapids Water Pollution Control Facility (standard deviations were 54 and 79% of the average values of and KS, respectively). From these results, a sampling and testing period of 8 to 10 tests over a three month period is recommended to accurately characterize the biodegradation performance of an activated sludge system with respect to specific organic compounds in the influent. This title belongs to WERF Research Report Series ISBN: 9781843396307 (eBook)

Characterization of recycled rubber media for hydrogen sulphide (H2S) control.

Hydrogen sulphide (H2S) adsorption capacities on recycled rubber media, tyre-derived rubber particle (TDRP™), and other rubber material (ORM™) have been evaluated. As part of the research, densities, moisture contents, and surface properties of TDRP™ and ORM™ have been determined. The research team findings show that TDRP™ and ORM™ are more particulate in nature and not highly porous-like activated carbon. The characteristics of surface area, pore size, and moisture content support chemisorption on the macrosurface rather than physical adsorption in micropores. For example, moisture content is essential for H2S adsorption on ORM™, and an increase in moisture content results in an increase in adsorption capacity.

Feasibility of Cooperative Development of Wetland Mitigation Projects in Iowa

The Iowa Department of Transportation (Iowa DOT) currently performs wetland mitigation on a project-by-project basis. At the same time, other agencies like the Iowa Department of Natural Resources and Natural Resource Conservation Service are performing wetland restoration projects, and counties and cities may be mitigating wetland losses as well. This project examined the feasibility of developing cooperative wetland mitigation projects in order to utilize state and local resources more efficiently to benefit both Iowa and local communities. The project accomplished the following objectives: (1) Identified and characterized cooperative wetland mitigation programs nationwide; (2) Developed a needs assessment through a survey of state, county, and large city agencies in Iowa to describe wetland mitigation programs and determine challenges with mitigation and program improvements, including long-term risks associated with maintenance and monitoring programs; (3) Surveyed state, county, and city agencies and organizations to identify resources available for developing cooperative mitigation projects and procedures; (4) Developed a conceptual framework for cooperative wetland mitigation.