Performance enhancement of large industrial wastewater stabilization ponds

A 6-month-long, bench-scale simulation of an industrial wastewater stabilization pond (WSP) system was conducted to evaluate responses to several potential performance-enhancing treatments. The industrial WSP system consists of an anaerobic primary (1ry) WSP treating high-strength wastewater, followed by facultative secondary (2ry) and aerobic tertiary (3ry) WSPs in series treating lower-strength wastewater. The 1ry WSP was simulated with four glass aquaria which were fed with wastewater from the actual WSP system. The treatments examined were phosphorus supplementation (PHOS), phosphorus supplementation with pH control (PHOS+ALK), and phosphorus supplementation with pH control and effluent recycle (PHOS+ALK+RCY). The supplementary phosphorus treatment alone did not yield any significant change versus the CONTROL 1ry model pond. The average carbon to phosphorus ratio of the feed wastewater received from the WSP system was already 100:0.019 (i.e., 2,100 mg/l: 0.4 mg/l). The pH-control treatments (PHOS+ALK and PHOS+ALK+RCY) produced significant results, with 9 to 12 percent more total organic carbon (TOC) removal, 43 percent more volatile organic acid (VOA) generation, 78 percent more 2-ethoxyethanol and 14 percent more bis(2-chloroethyl)ether removal, and from 100- to 10,000-fold increases in bacterial enzyme activity and heterotrophic bacterial numbers. Recycling a 10-percent portion of the effluent yielded less variability for certain physicochemical parameters in the PHOS+ALK+RCY 1ry model pond, but overall there was no statistically-detectable improvement in performance versus no recycle. The 2ry and 3ry WSPs were also simulated in the laboratory to monitor the effect and fate of increased phosphorus loadings, as might occur if supplemental phosphorus were added to the 1ry WSP. Noticeable increases in algal growth were observed at feed phosphorus concentrations of 0.5 mg/l; however, there were no significant changes in the monitored physicochemical parameters. The effluent phosphorus concentrations from both the 2ry and 3ry model ponds did increase notably when feed phosphorus concentrations were increased from 0.5 to 1.0 mg/l. ^

DISCHARGE PLANNING: A PROCESS MODEL

As the requirements for health care hospitalization have become more demanding, so has the discharge planning process become a more important part of the health services system. A thorough understanding of hospital discharge planning can, then, contribute to our understanding of the health services system. This study involved the development of a process model of discharge planning from hospitals. Model building involved the identification of factors used by discharge planners to develop aftercare plans, and the specification of the roles of these factors in the development of the discharge plan. The factors in the model were concatenated in 16 discrete decision sequences, each of which produced an aftercare plan.^ The sample for this study comprised 407 inpatients admitted to the M. D. Anderson Hospital and Tumor Institution at Houston, Texas, who were discharged to any site within Texas during a 15 day period. Allogeneic bone marrow donors were excluded from the sample. The factors considered in the development of discharge plans were recorded by discharge planners and were used to develop the model. Data analysis consisted of sorting the discharge plans using the plan development factors until for some combination and sequence of factors all patients were discharged to a single site. The arrangement of factors that led to that aftercare plan became a decision sequence in the model.^ The model constructs the same discharge plans as those developed by hospital staff for every patient in the study. Tests of the validity of the model should be extended to other patients at the MDAH, to other cancer hospitals, and to other inpatient services. Revisions of the model based on these tests should be of value in the management of discharge planning services and in the design and development of comprehensive community health services.^

Bench-scale evaluation of the activated sludge process for treatment of a high -strength chemical plant wastewater

A bench-scale treatability study was conducted on a high-strength wastewater from a chemical plant to develop an alternative for the existing waste stabilization pond treatment system. The objective of this study was to determine the treatability of the wastewater by the activated sludge process and, if treatable, to determine appropriate operating conditions, and to evaluate the degradability of bis(2-chloroethyl)ether (Chlorex) and benzene in the activated sludge system. Four 4-L Plexi-glass, complete mixing, continuous flow activated sludge reactors were operated in parallel under different operating conditions over a 6-month period. The operating conditions examined were hydraulic retention time (HRT), sludge retention time (SRT), nutrient supplement, and Chlorex/benzene spikes. Generally the activated sludge system treating high-strength wastewater was stable under large variations of organic loading and operating conditions. At an HRT of 2 days, more than 90% removal efficiency with good sludge settleability was achieved when the organic loading was less than 0.4 g BOD$\sb5$/g MLVSS/d or 0.8 g COD/g MLVSS/d. At least 20 days of SRT was required to maintain steady operation. Phosphorus addition enhanced the performance of the system especially during stressed operation. On the average, removals of benzene and Chlorex were 73-86% and 37-65%, respectively. In addition, the low-strength wastewater was treatable by activated sludge process, showing more than 90% BOD removal at a HRT of 0.5 days. In general, the sludge had poor settling characteristics. The aerated lagoon process treating high-strength wastewater also provided significant organic reduction, but did not produce an acceptable effluent concentration. ^