Water & Wastewater Asia Sep/Oct 2019

Water & Wastewater Asia • September / October 2019 24 | INSIGHT THE BEST SOLUTION – CONSIDER IT NOT ALWAYS BEING BEST FOR YOU In wastewater treatment, plants will most likely be challenged to find an efficient, reliable, and safe wastewater treatment solution that is also less costly to install, operate, and maintain, all while meeting the strictest local requirements. This challenge has not become easier, as dozens of suppliers are pushing various machines for thickening and dewatering, claiming that their technology is the best. Obviously, there is no ideal, universal solution because not every wastewater treatment process and its preconditions are the same, and every technology comes with process-related advantages and disadvantages alike. Even if only the economic arguments are considered, every project is specific, and nothing is set in stone. The variable elements could be the cost of sludge transport, the sludge’s final destination, the structure and quality in which it has to be transported, special treatment of Efficient sludge thickening and dewatering: How to find the right parameters for choosing the ideal solution By Christian Dousset, Process Technology Manager, ANDRITZ Sludge thickening and dewatering are key process stepswhen treatingwastewater. Numerous suppliers provide dozens of different machines to make this process easier – all claiming that their solution is the best, but often not taking account of the fact that several given parameters in a plant determine the success of the equipment chosen and consequently, the efficiency and profitability of operations. With no one-size-fit-all solution, how do plants find the one to fit their specific requirements? sludges in a wastewater treatment plant requiring dedicated equipment, the plant’s geographical location, whether or not a building already exists, specific constraints such as noise or odour, energy costs, availability of special reagents like powder and emulsion polymer, as well as qualitative discharge constraints like granulation or storage capabilities. SIZE DOES MATTER – CONSIDER YOUR SURROUNDINGS The required footprint of a machine is an essential factor in wastewater treatment plants, both those in planning and also those that are already up and running. When space is limited, a decanter centrifuge presents itself as a potential solution: Not only is the space required to install these machines smaller than for all other dewatering and/ or thickening units (which has an impact on the civil engineering costs), this technology also features an excellent capacity/size ratio. Its versatility in the treatment of various types of sludge, combined with this advantage, make it a popular solution – also for mobile dewatering units. But if conditions like a municipality’s population and the wastewater it produces are likely to change in the future, a gravity belt table seems to be a good thickening solution thanks to its high hydraulic capacity. Another thing to consider when checking whether a machine fits into a plant is the surroundings. Depending on the location and the neighbouring buildings, the noise from the machine as well as the ability to reduce the often-terrible odour coming from the treated sludge should not be left unconsidered when choosing the right technology. When noise and especially odour are of concern, it is better to choose a closed system instead of an open one – the reasoning behind this is simple: Foul odours and distractive sounds are contained if the system is enclosed. A common closed system for thickening with verified benefits in clean rooms and odour prevention is the drum thickener – which is also very compact in terms of capacity. When searching for a closed system for dewatering, a screw