Aluminum production wastes (APW) are produced during the recycling of aluminum scrap and dross. They are frequently disposed in dry form at Subtitle D nonhazardous waste landfills, where they may react adversely with liquids. Depending on the APW composition and landfill environment, the exothermic reaction can cause sustained temperature increases that inhibit normal anaerobic biodegradation. A constant pressure calorimeter test was developed to simulate the APW reaction in a basic environment and quantify the reactivity. APW reactivity was investigated under varying strengths of sodium hydroxide and particle size. Bench-scale calorimeter experiments show that concentrations greater than 4M NaOH oxidize metallic aluminum and increase temperatures rapidly to 100°C. Lower NaOH concentrations, such as 1M NaOH, are recommended to quantify the APW reaction in a constant pressure calorimeter. APW in neutral solutions was found to be stable, but reducing APW particles through ball-milling exacerbated reactivity.
Activated sludge that had been grown on a completely soluble wastewater in a pilot plant was subjected to aerobic digestion in batch, lab-scale reactors. During the course of digestion, destruction of nonvolatile solids occured so that is was preferable to express the kinetics of digestion upon the loss of total suspended solids rather than volatile suspended solids. The first-order rate constant for the destruction of degradable suspended solids was found to be unaffected by the solids retention time (SRT) at which the activated sludge had been grown, whereas the nondegradable fraction of the activated sludge was found to increase as the SRT increased.
The Federal Water Pollution Control Act Amendments of 1972 (PL 92-500) defined sec ondary wastewater treatment as that resulting in effluent concentrations of less than 30 mg/1 for 5-day biochemical oxygen demand (BOD5) and total suspended solids (tss) and a min imum of 85 percent removal for both param eters based on the plant's influent concentra tions. In spite of the relatively lenient nature of this standard, only 54 percent of the acti vated sludge plants surveyed by Environmen tal Protection Agency in 1975 were meeting it.1 One reason cited for this failure was in adequate operation. This is not to imply that the fault lies entirely with the plant operators. Instead this is an indication of the lack of interest which engineers have shown in the operation of the plants which they have de signed. It is the responsibility of engineers to develop theoretically sound yet easily applied operational techniques, so that they may be tried in the field. Then, if necessary, the re sults of their application can be used to modify the procedures, leading eventually to more effective ones. The purpose of this paper is to present a technique for operating the activated sludge process, which has resulted from 5 years of work using both computer simulation and pilot-plant testing. Although it has worked well in a 5.45 m3/d (1 gpm) pilot plant, it has not yet been tried in full scale. Thus, it is hoped that this report will lead to full-scale testing under a variety of situations so that the practical utility of the procedure may be eval uated. This paper will present the technique as a series of graphs and will emphasize their use for a number of purposes. Other papers develop the theory 2'3 and report how to gen erate the graphs for a particular installation.3 Two types of control can be applied to an activated sludge plant?short-term and long term. Short-term control seeks to smooth per formance by measuring changes in the influent as they occur and then adjusting an opera tional variable in response to those changes. To be effective, such techniques require auto matic monitoring and control, generally with the aid of an on-line computer. Although such control strategies are currently the sub ject of much research in large-scale plants, it will be some time before they are economically available to medium and small plants. In the meantime, many benefits can be achieved by long-term control, which is usually done man ually. Although adjustments of control var iables may be made within the plant on a daily or even hourly basis, the objective of long-term control is to hold a primary opera tional variable constant over long periods of time. The operational control procedure out lined herein is for long-term control. One of the most effective techniques for long-term control of an activated sludge plant is the maintenance of a constant solids reten tion time (srt).4'5 The srt is defined as the mass of mixed liquor suspended solids (mlss) maintained within the system divided by the mass lost from the system per unit time. The usual units for it are days. Because the srt is the reciprocal of the net growth rate of the organisms within an activated sludge system, maintenance of a relatively constant value will minimize changes in the efficiency of substrate removal and in the settleability of the solids in the final settler. Control of the srt requires
Municipal wastewater treatment plant operational data from ten secondary and nine advanced treatment facilities were analyzed to develop percentile-mean relations that summarize effluent BOD5 and suspended solids variability. Separate relations for daily, weekly, monthly, and 30-day running average effluent data are developed and plotted so that design effluent requirements can be easily estimated regardless of the particular type of BOD5 or suspended solids effluent limitation imposed.
La correlation des donnees de test de sedimentation avec l'indice de volume de boue permet d'appliquer la theorie de l'ecoulement de sedimentation a la conception et au fonctionnement de l'installation
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