Effect of aquifer storage and recovery (ASR) on recovered stormwater quality variability.

Aquifer Storage and Recovery (ASR) is increasingly being considered as a means of reusing urban stormwater to supplement available urban water resources. Storage of stormwater in an aquifer has been shown to affect water quality but it has also been claimed that storage will also decrease the stormwater quality variability making for improved predictability and management. This study is the first to document the changes in stormwater quality variability as a result of subsurface storage at four full scale ASR sites using advanced statistical techniques. New methods to examine water quality are required as data is often highly left censored and so traditional measures of variability such as the coefficient of variation are inappropriate. It was observed that for some water quality parameters (most notably E. coli) there was a marked improvement of water quality and a significant decrease in variability at all sites. This means that aquifer storage prior to engineered treatment systems may be advantageous in terms of system design to avoid over engineering. For other parameters such as metal(loids)s and nutrients the trend was less clear due to the numerous processes occurring during storage leading to an increase in variability, especially for geogenic metals and metalloids such as iron and arsenic. Depending upon the specific water quality parameters and end use, use of ASR may not have a dampening effect on stormwater quality variability.

Application of a risk management framework to a drinking water supply augmented by stormwater recharge.

The Blue Lake is an important water resource for the city of Mount Gambier and the surrounding region, primarily as the drinking water supply source, but also as a tourist attraction. Mount Gambier's stormwater is discharged directly via drainage wells into the unconfined, karstic Gambier Limestone aquifer, which in turn provides the majority of recharge to Blue Lake. Discharge of urban runoff to the aquifer commenced in the 1800s as a means of stormwater management, but is now recognised as contributing to the drinking water supply in Blue Lake. Recently, guidelines for managing the risks associated with water recycling and augmenting drinking water supplies have been developed. This paper examines the organic chemical hazards associated with a stormwater to potable recycling scheme as an example of the current risk management framework.

Factors affecting the performance and risks to human health of on-site wastewater treatment systems.

Aerobic wastewater treatment systems (aerobic systems) are the preferred choice in a region overlying a karstic aquifer used for drinking water supplies, as they are thought to provide better protection to groundwater and human health than standard septic systems. However, aerobic systems in operation do not always perform to design standard; while this is often blamed on lack of maintenance, few studies have investigated the link directly. This study investigates the performance of domestic on-site wastewater treatment systems in South Australia, and compares effluent quality to maintenance records. Effluent from 29 septic tanks and 31 aerobic systems was analysed for nutrients, physico-chemical parameters and microbiological indicators. Aerobic systems generally provided greater treatment than septic tanks, yet most aerobic systems did not meet regulatory guidelines with high levels of indicator bacteria in 71% of samples. The effect of system size, number of household occupants and maintenance on aerobic system treatment performance was analysed: chlorine levels were positively correlated with time of last service, and nutrient concentrations were positively correlated with the number of occupants. A microbial risk assessment revealed the observed irrigation practices to be high risk; and sufficient residence time in the aquifer cannot be guaranteed for protection of groundwater used for drinking. Additional preventive measures such as irrigation management or post treatment of drinking water supply (such as UV disinfection) are required to meet public health targets.

Effect of alum treatment on the trihalomethane formation and bacterial regrowth potential of natural and synthetic waters.

Waters from five reservoirs and "synthetic waters", prepared using terrestrially derived dissolved organic matter (DOM) extracted from vegetation and reservoir catchment soils, were studied for their treatability with alum using a jar test procedure. DOM in drinking water is a precursor for the formation of trihalomethanes (THM) following chlorine disinfection and can also be a substrate for microbial growth in the drinking water distribution system. The trihalomethane formation potential (THMFP) represents an upper concentration limit on THMs formed by chlorination, while bacterial regrowth potential (BRP) is an indicator of the bioavailability of DOM. BRP and THMFP were measured before and after alum treatment and the results were related to the source of the DOM. It was found that freshly derived terrestrial DOM in synthetic water resulted in higher THMFP and BRP than DOM in reservoir waters. For the samples investigated, conventional alum treatment did not always reduce the THM precursor levels formed in laboratory tests below the NH&MRC (1996) guideline level of 250 microg/L nor produce microbially stable waters.

Variability of the obturator vessels.

The obturator artery and vein are usually described as branches or tributaries of the internal iliac vessels although variations with connections to the external iliac or inferior epigastric vessels have been reported. Because these anomalous vessels are at risk in groin or pelvic surgeries that require dissection or suturing along the pelvic rim, we measured the frequency of these variations in 105 pelvic walls (45 in the United States and 60 in China). Our data show that 70-82% of pelvic halves and 83-90% of whole pelves had an artery, vein, or both in the variant position. Arteries were most often found in the normal position only but normal and anomalous veins were most frequently found together. These data show that it is far more common to find a vessel coursing over the pelvic rim at this site than not and have implications for both pelvic surgeons and anatomists.

The clinical anatomy of laparoscopic inguinal hernia repair.

Laparoscopic approaches for abdominal surgery are being used with increasing frequency. Their advantages are sometimes negated by the disturbing incidence of postoperative sequelae. In the case of inguinal hernia repair, these are often the result of failing to understand that the anatomy of the anterior approach to the abdominal wall cannot necessarily be directly applied to laparoscopy. The inguinal ligament, easily identified in an anterior approach, is only seen laparoscopically after removal of the iliopubic tract, a key structure which lies in the plane of the original defect of most groin hernias. Thus, an understanding of the incompletely trilaminar anterior abdominal wall, including the iliopubic tract, is the foundation for effective inguinal hernia repair using any approach (anterior or posterior) or technique (sutures, mesh or staples). Laparoscopic inguinal hernia repair has produced an increase in the frequency of debilitating neuropathies, most notably of the lateral femoral cutaneous nerve (LFCN). This is directly related to the variable intrapelvic course of this nerve or its branches. In more than 13% of the 114 pelves we examined, the LFCN was within 0.5 cm of the iliopubic tract or in the vertical plane of the anterior superior iliac spine, key lateral landmarks and anchoring sites for mesh in laparoscopic hernia repairs. Medial landmarks also have variable features. These data indicate that the identity of anatomical landmarks and the variability of other structures will continue to be important in the successful development of new laparoscopic techniques.

Variations in the inferior pelvic pathway of the lateral femoral cutaneous nerve: implications for laparoscopic hernia repair.

Laparoscopic repair of inguinal hernias is gaining acceptance in the repertoire of the general surgeon. However, nerve entrapment sequelae have been reported and appear to be higher with the laparoscopic approach. Contributing factors include pelvic variations in nerve pathways and the use of staples. We examined the pelvic relations of the lateral femoral cutaneous nerve (LFCN) to the anterior superior iliac spine (ASIS) and the iliopubic tract (IPT) because of the high morbidity of entrapment of this nerve, despite its low incidence. The LFCN, ASIS, and IPT were identified and their relationships measured in 48 male and 24 female cadavers ranging in age from 61 to 96 yr. The LFCN was located 1.7 (+/- 1.2) cm medial to the ASIS along the IPT and 1.4 (+/- 0.7) cm posterior (deep) to the IPT at this point, with no significant sex differences. The intrapelvic pathway of the LFCN, including its branches, varied widely so that in 18% of these specimens the LFCN was in either the vertical plane of the ASIS (13%) or in the plane of the IPT (5%). In 11% this nerve was within 1 cm of the ASIS. These data indicate that exclusive use of the ASIS as a guide for staple placement may result in entrapment of this nerve or its branches.

Correlation between mammography and the pathology of nonpalpable breast lesions.

One hundred consecutive needle localization biopsies were performed for nonpalpable breast lesions discovered on low-dose mammography of asymptomatic women between June, 1984, and August, 1986. Malignant disease was found on 21 biopsies. Four were carcinoma in situ, and 17 were infiltrating carcinomas. Only three of the infiltrating carcinomas had metastasized to regional nodes, as confirmed by subsequent axillary dissection. Two of these metastatic tumors involved two nodes and the third only one. The findings on the remaining 79 biopsies were benign. Forty-eight mammograms were read as "benign"; all (100%) were benign pathologically. Thirty-one mammograms were considered "malignant"; 19 (61%) were malignant pathologically. Only two of the 21 mammograms given "suspicious" interpretations were malignant. Microcalcifications correlated with malignancy only 30% of the time (12/42).

Intestinal anastomosis after preoperative radiation therapy for carcinoma of the rectum.

A retrospective review was conducted on 133 patients who underwent anterior resection and primary intestinal anastomosis for adenocarcinoma of the rectum from 1973 to 1983 at the Baystate Medical Center. Forty patients received a moderate dose, 4,500 rads, of radiation therapy preoperatively. Twenty-six of these patients (65 per cent) underwent protective colostomy at operation. An additional 93 patients underwent an operation without radiation and 38 of these (42 per cent) had a colostomy. We found no significant difference between patients who did or did not undergo radiation therapy in the over-all rate of complications (25 per cent for those who underwent radiation and 29 per cent for those who did not). Furthermore, there was no significant difference in anastomotic leak rates between the two groups (10 and 7 per cent respectively), even after controlling for the presence of a protective colostomy. We did find that leak rates for both groups were markedly higher for patients with a colostomy (14 per cent) than for patients without (1 per cent) (p less than 0.005). We conclude that a moderate dose of radiation therapy preoperatively does not increase the risk of anastomotic leakage or other operative complications with anterior resection. Colorectal intestinal anastomosis may be safely performed without routine colostomy after planned preoperative adjuvant radiation therapy if the anastomosis is technically satisfactory.

Apathetic thyrotoxicosis presenting as an abdominal emergency: a diagnostic pitfall.

Thyrotoxicosis may present with a hyperkinetic clinical picture typically associated with Graves' or Plummer's disease, or in an apathetic form characterized by lethargy, weakness, and withdrawal. Both the hyperkinetic and apathetic forms of thyrotoxicosis may be associated with or masked by predominantly extrathyroidal manifestations, occasionally referable primarily to the abdomen. We present two cases of apathetic thyrotoxicosis that suggested the need for urgent surgical intervention, and review the literature on apathetic thyrotoxicosis as an abdominal emergency, as well as laboratory studies and possible etiology.