Hong Kong wastewater - now and future

Hong Kong wastewater - now and futur

An optimization model - preliminary selection of appropriate technology in wastewater treatment alternatives

This research is concerned with the use of techniques of system analysis / operations research in the selection of the optimal - or most appropriate - wastewater treatment techniques in any given situation. An extensive investigation of existing treatment system optimization models, applying techniques of linear programming, dynamic programming and non-linear mathematical programming, has been carried out. None of these existing models deals with the socio-cultural and environmental conditions but merely with the economy of treatment. In this work the more subjective or intangible factors are included in the proposed optimization model in which twenty parameters are identified. These parameters are considered to be most important in the selection of appropriate alternatives for treating municipal wastewater. They include technical, economic, environmental and socio-cultural factors. The model was developed to rank a definite number (n) of wastewater treatment alternatives (decision variables) by the evaluation of the twenty parameters [...continues]

Strategic sewage disposal in Hong Kong

In my previous paper presented in the 21st WEDC Conference (Tang, 1995), the overall strategy used to tackle wastewater produced in the whole territory of Hong Kong was described. Also briefly mentioned in that paper was a mega scale project named “Strategic Sewage Disposal Scheme” which is being undertaken in Hong Kong. The scheme is not a solution to the water pollution problems in the whole territory but is only for solving the problems at the most densely populated urban areas, viz, Kowloon Peninsula, northern part of Hong Kong Island, and the harbour (named Victoria Harbour) separating Kowloon Peninsula and Hong Kong Island (see the rectangular frame in Figure 1). The current paper is to give a detail discussion on the strategic sewage disposal scheme (SSDS)

Treatment of mixed (fresh and salt) wastewater

Hong Kong has the geographical advantage of being situated on the coast and therefore it is possible to use dual water supply systems (fresh + sea water systems in two separate distribution networks) for potable and non-potable uses. From the sea water supply system, about three quarters of the population in Hong Kong is supplied with salt water for toilet flushing. The seawater is extracted from the sea directly and pumped by pumping stations located near the shore and supplied to the households. The used toilet flushing water (saline wastewater) is discharged into the sewerage system which conducts the mixed (fresh + salt) wastewater into the STW (sewage treatment works). The salt concentration of the mixed wastewater is between 5,000 mg/l to 6,000 mg/l, about one-fifth of seawater salt concentration, in Hong Kong

Economy of dual water supply systems

Hong Kong is one of the very few coastal cities in the world which utilize “dual water supply systems”. The dual water supply involves two distribution systems, one fresh water distribution system for potable use and another seawater system for toilet flushing and fire fighting purposes. The details of such dual water supply systems have been given in a paper (Tang, 2000) published in the Proceedings of the 26th WEDC Conference. The objective of this paper is not to repeat what has been described in said paper but to report a comparison of the economy of (1) a single distribution system (fresh water supply only) and (2) the dual water supply systems. In other words, the question addressed in this paper is: would it be more economical for Hong Kong to use a single distribution system instead of the existing dual systems

Predictors of short-term clinical response to cardiac resynchronization therapy

Aims: Cardiac resynchronization therapy (CRT) reduces morbidity and mortality in patients with symptomatic heart failure and QRS prolongation but there is uncertainty about which patient characteristics predict short-term clinical response. Methods and results: In an individual patient meta-analysis of three double-blind, randomized trials, clinical composite score (CCS) at 6 months was compared in patients assigned to CRT programmed on or off. Treatment–covariate interactions were assessed to measure likelihood of improved CCS at 6 months. MIRACLE, MIRACLE ICD, and REVERSE trials contributed data for this analysis (n = 1591). Multivariable modelling identified QRS duration and left ventricular ejection fraction (LVEF) as predictors of CRT clinical response (P < 0.05). The odds ratio for a better CCS at 6 months increased by 3.7% for every 1% decrease in LVEF for patients assigned to CRT-on compared to CRT-off, and was greatest when QRS duration was between 160 and 180 ms. Conclusions: In symptomatic chronic heart failure patients (NYHA class II–IV), longer QRS duration and lower LVEF independently predict early clinical response to CRT

Endolymphatic sac tumour

We present a case of a papillary tumour at the cerebellopontine angle in a 41-year-old man. He presented with left-sided facial and ear pain associated with dizziness, nystagmus and hearing loss. CT scan of the temporal bone showed a destructive tumour at the left cerebellopontine angle. Surgical excision was performed and the diagnosis of the endolymphatic sac tumour was made. Endolymphatic tumour is a low grade adenocarcinoma that originates from the endolymphatic sac. The defi nitive diagnosis requires a combination of clinical features, radiological finding and pathological correlation

Ventricular defibrillation using biphasic waveforms: The importance of phasic duration

AbstractBiphasic waveforms can be used to defibrillate the heart with less energy than that used by monophasic waveforms. In 14 anesthetized open chest dogs with large contoured defibrillation electrodes, the effect on defibrillation efficacy of varying the duration of the two phases of biphasic waveforms was studied. All combinations of 0, 1, 3.5, 6 and 8.5 ms duration were used for both the first and the second phase except for the meaningless case in which both durations were 0 ms. The 3.5-2 waveform (3.5 ms first phase and 2 ms second phase) was also tested.All the hearts were defibrillated with ⪯5 joules using any of the 25 waveforms. However, biphasic waveforms with the second phase shorter than or equal to the first had significantly lower defibrillation thresholds than did those with the second phase longer than the first or than did monophasic waveforms of approximately the same total duration. A plot of defibrillation threshold current strength versus second phase duration for all biphasic waveforms with a 3.5 ms first phase did not produce a hyperbolic strength-duration curve as seen with monophasic waveforms. To verify these findings, defibrillation dose-response curves were obtained for the 3.5-2, 6-6 and 3.5–8.5 biphasic waveforms in another six dogs. The 50 and 80% successful voltage doses of the 3.5–8.5 waveforms were significantly higher than those of the other two waveforms, which were not different from one another.In conclusion: 1) phasic durations of biphasic waveforms are important determinants of defibrillation efficacy and biphasic waveforms with the second phase shorter than the first are more effective than are those with the reverse sequence; 2) the strength-duration relation for the defibrillation threshold is different for biphasic and monophasic waveforms; 3) defibrillation of the canine heart can be achieved with low energy with use of large contoured pericardial electrodes and suitable biphasic waveforms

FISH karyotype of 85 common wheat cultivars/lines displayed by ND-FISH using oligonucleotide probes

Fluorescence in situ hybridization (FISH) can reveal minor structural differences of chromosomes. The karyotype of common wheat (Triticum aestivum L.) based on FISH pattern is seldom reported. In this study, non-denaturing FISH (ND-FISH) using Oligo-pSc119.2-1, Oligo-pTa535-1 and (AAG)6 as probes was used to investigate the chromosomal structure of 85 common wheat including 83 wheat-rye 1RS.1BL translocation cultivars/lines, a wheatrye 1RS.1AL translocation cultivar Amigo and Chinese Spring (CS). Two, three, two, three, six, three and four structural types respectively for 1A, 2A, 3A, 4A, 5A, 6A and 7A chromosomes were observed. Two, eight, two, two, four and six types of chromosome for 2B, 3B, 4B, 5B, 6B and 7B were respectively detected. The structure of 1B chromosomes in Amigo and CS is different. Five, two, two and two types of chromosomal structure respectively for 1D, 2D, 3D and 5D were distinguished. Polymorphisms of 1RS.1BL, 4D, 6D and 7D chromosomes were not detected. Chromosomes 1AI, 2AI, 3AI, 4AI, 5AIII, 6AI, 7AIII, 2BI, 3BV, 4BI, 5BII, 6BIII, 7BI, 1DIV, 2DI, 3DI and 5DII appeared in these 85 wheat cultivars/lines at high frequency. Each of the 85 wheat cultivars/lines has a unique karyotype. Amigo is a complex translocation cultivar. The FISH karyotype of wheat chromosomes built in this study provide a reference for the future analyzing wheat genetic stocks and help to learn structural variations of wheat chromosomes. In addition, the results in this study indicate that oligonucleotide probes and ND-FISH technology can be used to identify individual wheat cultivar