Monday 12 August 2013

Green waste disposal & power generation for large-scale medical facilities!

The Dutch company Pharmafilter has developed a waste disposal model for large-scale medical facilities which combines wastewater treatment with waste disposal and biogasbased power generation. The Siemens Industry Automation Division supplied automation technology, process instrumentation, measuring and analyzing systems as well as the metrological concept for initial installation of the model in the Reinier-de-Graaf hospital in Delft (NL). The project has resulted in reduced waste, contaminantfree wastewater, improved hygiene and simplified logistical processes.

The process technology implemented by Pharmafilter for the green solution trialed in the Reinier-de-Graaf hospital in Delft can be adapted and scaled up as required. The underlying concept entails the convergence of solid waste and wastewater flows, their combined treatment and the use of biodegradable disposables. From the extensive Siemens process analytics and instrumentation portfolio, Sitrans measuring instruments and Ultramat gas analysers support the safe generation of biogas by supplying a continuous stream of precise information about temperature, flow rate, level or pressure. Siwarex load cells are used for determining the precise weight of the substrate used in the fermenter.

The waste disposal model used in Delft is based on the principle of recycling in preference to multiple use. In conventional hospitals, cutlery and medical utensils such as bedpans are gathered, cleaned, and transported to another location for repeated use. In Delft, these utensils are made of biodegradable materials: renewable raw materials based on starches and sugars. Biopolymers demonstrate the same properties as conventional plastics but are not based on mineral oils and can be fully biologically degraded. Instead of sending utensils or bedpans along the laborious journey needed before they can be re-used, everything is fed directly into special shredders without the need to be emptied, cleaned or handled in any other way. The shredders mill the waste and forward it via the hospital’s existing water/wastewater system to the on-site sewage plant.
The treatment of hospital wastewater poses a major challenge: Municipal sewage facilities are primarily designed for the elimination of biologically degradable materials and the removal of nutrients such as phosphorous and nitrogen compounds. Even the most up-to-date treatment methods are not able to eliminate high concentrations of drug residues, x-ray contrast media or pathogens. Even though no direct hazard to human health has yet been proven to result from these waste products, there is no doubt about their impact on the aquatic habitat, for instance as a result of waterborne hormonally active substances. In order to put a stop to pollution of the aquatic system by this type of residue, the use of decentral water treatment plants directly on the hospital site approach. Delft Hospital’s sewage plant has an annual capacity of 60,000 cubic meters of wastewater and 200 tons of solid waste matter. The purification concept was additionally combined with a biogas generation process.

Waste containing fats and carbohydrates from the ward shredders, separated according to solids and fluids, is used as the substrate for anaerobic digestion in the fermenter. At just under 60 degrees Celsius, the biomass undergoes microbial transformation into substances including methane and carbon dioxide. The waste water flows through several purification stages, during which the
biomass is separated by membrane modules and all sludge structures as well as colloidal matter are removed by means of ultrafiltration. Ozone treatment eliminates pathogens and drug residues. The last purification stage involving active carbon removes any still remaining medicine residues and hormone disrupting trace elements. As the average purification rate is at least 98 percent, and consequently well above the statutory requirement, the purified product may be safely introduced into the surface water or used for irrigation.

The generation and subsequent conversion of biogas from organic waste almost completely meets the plant’s own energy supply requirement. To achieve this, the complex processes taking place in the fermenter require optimum environmental conditions. Continuous process control using tailor-made measuring and analyzing systems plays a decisive role in ensuring the system’s success. If key parameters such as acid content or temperature are incorrect, the balance of the anaerobic process is compromised, resulting in total failure of the plant.

The green solution has proven a resounding success from every point of view. The volume of waste has been ducts has improved hygiene standards and driven down logistical costs. The scheme has also meant improved patient safety, a reduced workload for nursing staff and environmental benefits resulting from water purification and the use of waste matter as a source of energy. reduced by more than half, and the wastewater is almost free of contaminants. The use of disposable pro presents itself as the most practical

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