A mathematical technique for the design of near-zero-effluent batch processes

Wastewater minimisation in chemical processes has always been the privilege of continuous rather than batch plants. However, this situation is steadily changing, since batch plants have a tendency to generate much more toxic effluent compared to their continuous counterparts which are usually encountered in bulk manufacturing. Past methodologies for wastewater minimisation in batch processes have focused on operations based on mass transfer. They do not take into consideration the reuse of wastewater as part of product formulation. Reusing wastewater in product formulation has the major advantage of negating much of the effluent produced, thereby enabling a process to operate in an almost zero-effluent manner. Presented in this paper is a mathematical technique for the simultaneous design and scheduling of batch operations operating in a near-zero-effluent manner. The technique determines the number and size of the processing vessels, while ensuring maximum water reuse in product. The technique was applied to an illustrative example, and an 80% savings in wastewater was achieved, with a corresponding plant design that achieves the required production.Keywords: zero-effluent, batch process, wastewater minimisatio

Patterns of disease on admission to children’s wards and changes during a COVID-19 outbreak in KwaZulu-Natal Province, South Africa

Background. Major causes of under-5 child deaths in South Africa (SA) are well recognised, and child mortality rates are falling. The focus of child health is therefore shifting from survival to disease prevention and thriving, but local data on the non-fatal disease burden are limited. Furthermore, COVID-19 has affected children’s health and wellbeing, both directly and indirectly.Objectives. To describe the pattern of disease on admission of children at different levels of care, and assess whether this has been affected by COVID-19.Methods. Retrospective reviews of children’s admission and discharge registers were conducted for all general hospitals in iLembe and uMgungundlovu districts in KwaZulu-Natal Province, SA, from January 2018 to September 2020. The Global Burden of Disease framework was adapted to create a data capture sheet with four broad diagnostic categories and 37 specific cause categories. Monthly admission numbers were recorded per cause category, and basic descriptive analysis was completed in Microsoft Excel.Results. Overall, 36 288 admissions were recorded across 18 hospital wards, 32.0% at district, 49.8% at regional and 18.2% at tertiary level. Communicable diseases, perinatal conditions and nutritional deficiencies (CPNs) accounted for 37.4% of admissions, non-communicable diseases (NCDs) for 43.5% and injuries for 17.1%. The distribution of broad diagnostic categories varied across levels of care, with CPNs being more common at district level and NCDs more common at regional and tertiary levels. Unintentional injuries represented the most common cause category (16.6%), ahead of lower respiratory tract infections (16.1%), neurological conditions (13.6%) and diarrhoeal disease (8.4%). The start of the local COVID-19 outbreak coincided with a 43.1% decline in the mean number of monthly admissions. Admissions due to neonatal conditions and intentional injuries remained constant during the COVID-19 outbreak, while those due to other disease groups (particularly respiratory infections) declined.Conclusions. Our study confirms previous concerns around a high burden of childhood injuries in our context. Continued efforts are needed to prevent and treat traditional neonatal and childhood illnesses. Concurrently, the management of NCDs should be prioritised, and evidence-based strategies are sorely needed to address the high injury burden in SA

Efficacy of Chemical Oxidation and Coagulation for COD and Color Reduction from Pulp Mill Effluent

In a pulp and paper mill, the highly colored wastewater generated from the pulping process requires pretreatment before the biological purification process because of the presence of recalcitrant lingo-cellulosic compounds. For the present study, the black liquor was prepared in the laboratory by digesting the sugarcane baggase using the soda process, which was further diluted before use in the experimental study. The wastewater [pH = 13.0, chemical oxygen demand (COD) = 5, 120 mg/L] was treated by two processes: wet oxidation (WO) (both noncatalytic and catalytic) and coagulation. Catalytic WO (CWO) experiments were conducted in the presence of 60% CuO/40% CeO2 at temperatures ranging from 130 to 170 degrees C and total pressures of 0.95 MPa. During the CWO process, the maximum COD and color removals were found to be approximately 51 and 71%, respectively. Coagulation followed by noncatalytic WO exhibited the best performance with overall COD and color reductions of approximately 77.5 and 87%, respectively. The biodegradability of the wastewater was increased to 0.60 and 0.96 after CWO and combined treatment, respectively, from an initial value of 0.22. DOI: 10.1061/(ASCE)EE.1943-7870.0000611. (C) 2012 American Society of Civil Engineers

Optimum Design of Waste Water Treatment Network

Various environmental regulations imply that it is important to minimize the cost associated with treatment of different industrial wastes prior to its discharge to the environment. In this paper, an algebraic methodology, based on the principles of process integration, is proposed to target the minimum waste treatment flow rate to satisfy an environmentally acceptable discharge limit. In the proposed methodology, treatment units with fixed outlet concentrations are considered. It is observed that it is not necessary to maximize the usage of the treatment unit with the minimum specific cost. Hence, a prioritized cost for each treatment unit is devised to select appropriate treatment units that minimize the overall operating cost. Applicability of the proposed methodology is demonstrated through examples

Industrial heat utilisation through water management

The focus of this article is on the dependence between water and energy in industry and the way these resources can be managed in an integrated and more sustainable manner. The fundamental methodology supporting the concept of simultaneous management of water and energy is the process systems approach guided by deep understanding of the simultaneous mass and heat transfer, considering phase and pressure changes. Special attention in this case is paid to the utilization of the latent heat of water evaporation and condensation (allowing for water and heat recycling). The article takes a new view of water solutions management, especially when processes experience difficulties for direct heat recovery. The article also highlights the links between water management, heat recovery, process efficiency improvement, and capacity de-bottlenecking, which bring additional positive impact of proposed methodologies. The advantages of efficiency improvement, water saving, and improved environmental impact of proposed solutions are analyzed and demonstrated for an industrial case