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Water Quality#

Overview#

pysimdeum treats water quality calculations as a post-processing step after simulation. Simulated wastewater profiles in the form of a discharge object are the assumed input for both nutrient and temperature calculations.

Info

Note that water quality calculations are applied outside the simulation stage and will not be generated when simulating discharge patterns.

Nutrient Concentrations#

Methodology#

The nutrient concentration calculations in pysimdeum are performed using a series of steps that process simulated discharge profiles and enrich it with nutrient concentrations based on input statistics from a wastewater nutrient config. These calculations inclusde steps to manipulate data from xarray.Dataset and xarray.DataArray objects, converting them to pandas.DataFrame objects for easier manipulation and calculation.

  1. Data extraction and enrichment

    • Discharge data is extracted from discharge object (xarray.Dataset) and converted to a pandas.DataFrame. This DataFrame is then enriched with metadata, including usage and event_label columns, based on the discharge event metadata provided in the dataset.

  2. Nutrient sampling

    • Nutrient concentrations (g/use) are sampled from a truncated normal distribution. The mean values for the distribution are read from a TOML config file, which contains statistics for enduse and usage type level, i.e. difference nutrient concentrations for urine and faeces use of a Wc enduse.

  3. Nutrient concentration

    • The nutrient concentration for each discharge event is calculated by dividing the sampled nutrient value by the total flow for the discharge event, resulting in a concentration in grams per liter (g/L).

  4. Temporal aggregation

    • The user can input the period of time aggregation that the output is required in. This can be in seconds, minutes, 15 minutes, 30 minutes, or hourly periods. Defaults to hourly.

Info

Note that the period of temporal aggregation selected will affect runtime. Only aggregate in seconds if necessary, as this will significantly increase runtime especially when simulating multiple houses.

Temperature#

Methodology#

The discharge temperature calculation in pysimdeum is performed using a series of steps that process simulated discharge profiles and enriches it with end use discharge temperature based on values provided in the end use config files. For the Dishwasher and WashingMachine enduses, a discharge temperature is sampled for each cycle from a range defined in the config files. Similarly to the nutrient concentrations, the calculations inclusde steps to manipulate data from xarray.Dataset and xarray.DataArray objects, converting them to pandas.DataFrame objects for easier manipulation and calculation

  1. Data extraction and enrichment

    • As above in the nutrient concentrations, data is extracted from discharge object, converted to a pandas.DataFrame and enriched with metadata.

  2. Proportional Temperature Calculation

    • The discharge temperature is calculated by computing a weighted average temperature at each event, this outputs a discharge temperature proportional to the end use discharge flow.

  3. Temporal aggregation

    • The user can input the period of time aggregation that the output is required in. This can be in seconds, minutes, 15 minutes, 30 minutes, or hourly periods. Defaults to hourly.

Info

Note that this is calculating the discharge temperature at the point when it leaves the end use. In reality temperature changes over time so this figure may not represent the exact temperatures.