1. Where are we?
Process water play a very important role within ceramic activities, being involved in a wide range of production’s steps. If one the one hand they are strictly necessary to the course of the work, they can lead on the other hand to problems when they do not fits the required production parameters.
It is not easy to fix on the map the very point at which issues emerge, since they are heterogeneous and non-standard. It is therefore established to conventionally identify their presence (on the our metro tube) in the production step where they appear first:
- MACRO-PHASE: STORAGE OF RAW MATERIALS
- PHASE: PROCESS WATER
2. Origin of the waters
As many know, we assume that ceramic production is a closed-cycled system within which process water mostly derive form in-house production activities.
It is therefore a question of WASTE WATER mainly deriving from the grinding department as well as from the post-firing activities, such as cut and polishing. This implicitly means that ceramic companies, as is well known, tend to recycle water both in order keep costs and to reduce environmental impact: a question, now more than ever, extremely relevant and unavoidable. Together with this recycle’s activity, it is also important to take into consideration all waters that do not derive from the company’s internal closed-cycle but that come directly from outside.
We are basically talking about:
- MAINS WATER (that is controlled and stable over time, mainly used in the glazes’ grinding department)
- WELLWATER (that instead needs more detailed inspections)
3. Water's features and critical issues
Process waters – i.e. all those waters that move to storage tanks from the glazing line, grinding mills or other process steps – are made of a very heterogeneous mix. For the purpose of our investigation about the issues that they may provide, we limit here a short list of the most important contents:
- Adhesive residues
- Glaze residues
- Raw materials residues
How do these elements affect the application?
How can they interact with processes?
The presence of ORGANIC MATTER within process water together with its environmental exposure means that waters can enrich themselves over time both of bacterial colonies and microorganisms leading to very rapid degradations.
Bacterial degradations may produce in turns an important increasing of WATER CONDUCTIVITY that, simplifying, we could define as the ability of a liquid to transmit electricity.
The conductivity value is directly affected by the water’s content of ions. We could generally say that the greater is the content of ions (or of the ionic charge) and the higher is the water conductivity.
Why is it important to constantly check the water conductivity’s values?
An high conductive water can be a troublemaker during application because it may affect, for example, the slurries or glazes’ viscosity. In some cases the conductivity reaches such high values that – to fit within the proper parameters and so to proceed with a proper application – more water must be added in the process, therefore affecting both the productivity as well as the environment.
- The increase of water content per kg obviously reduces the solid percentage within the suspension, leading to a lower hourly production of spray-dried product during atomization.
- The lower hourly production of atomized powder together with the higher amount of water produce in turns a more important energy cost, also influencing a higher production of C02(carbon dioxide): the more water has to evaporate the more quantity of emissions is produced
4. Conductivity & Groundwater
The critical issue promoted by waters’ conductivity (that chemically speaking is due to an excessive presence of multivalent cations such as calcium and magnesium) also and especially relates to groundwater that, coming from deep under the ground, is by its nature subject to variations depending on the season. Especially on our territory (Sassuolo district).
During summer, for example, the massive withdrawal of groundwater, together with the less frequent rains, lead to a dip in the waters level and therefore to an increase in the ionic concentration (and so in the conductivity). It’s not by chance that problems related to conductivity can much further emerge at the end of the summer months.
5. Actions & Solutions
Process waters often require different kinds of treatment in order to perform at the best and avoid production problems. These treatments can vary from company to company according with the specific production parameters.
- A. WATER CLARIFICATION
Water clarification process is certainly one of those.
It is developed through a flocculation and decantation process, followed by a filter-pressing process of the suspended particles inside the water.
- B. SANITIZATION
Beside the water clarification process, it would be important to proceed with a detailed study of the water cycle in order to take action with a SANITIZING and/or PRESERVATION process. The main target is obviously to break down microorganisms and bacteria by means of proper preservative and sanitizing agents. A grinding water containing bacteria may for example lead to a bacterial proliferation inside the slurry after the grinding process. The situation could get even worse thanks to the slurries organic content (of which bacteria feed).
- C. pH CONTROL
It is also very important to check the water basic parameters and especially its pH value. These controls should be used to make any preventive corrections in case of very non-standard parameters (in our case the ideal water’s pH value is about 8.5 / 9).
A too acid pH could for example worsen the slurry’s viscosity value as well as the slurry’s flow.
- D. EVALUATION OF WATER DERIVING FROM PURIFIERS & TANK STORAGE
Two last measures that could be useful to avoid problems.
- Carefully evaluate the water deriving from purifier: even if it has an harmless-looking, it could hide some traps (such as containing not negligible amount of flocculants residues)
- Stock water process inside big tanks in order to manage possible fluctuation at the best
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