B3 - Test run

B3 - Test run
Batch digestion tests with controlled input
Calibration of COWS subsystem
Incremental optimisation of the full process
Test of operational limits
M - Validation of full scale COWS process
D5 - COWS performance report

---

Description and methods employed (what, how, where and when)

The main purpose of this test run action is to get:

• optimal processing through the COWS pre-treatment prototype subsystem;
• optimal overall performance of the plant

In order to achieve this goal adjustment and balancing of process parameters are to be done.

Adjustments of COWS pre-treatment prototype subsystem depend on the technology adopted; they are anyway similar in both cases of screw-press and piston-press (the most probable technologies). It would be different for hydro-mechanical separation.

We take as reference the extrusion process.

In order to evalute the performance of pre-treatment unit (COWS prototype) the presence of contaminants will be consider the principal factor. Tests include both chemical, physical, and ingredient analyses. The following contaminants/contrary materials are measured (relative to the organic fraction)

• Putrescible
• Plastics
• Metals
• Glass
• Textiles
• Wood
• Paper
• Inerts

Adjustments should consider the performance of each stage and the effects on subsequent steps. Characterization will be made at each step on residuals and in-flow materials, starting from influent OFMSW characterisation. Following steps are:

• after pre-treatment, out of the press/screw system;
• mixer content (floating, pulp precipitate, pulp outflow);
• digester (fermentation values and digestate)
• supernatants

Main process data monitored are:

• Chemical composition of OFMSW and WAS influent (average monthly)
  • TS, g/kg
  • TVS, %TS
  • TCOD, mgO2/l
  • TKN, mgN/l
  • Ptot, mgP/kgTS
  • Alkalinity, mgCaCO3/l
  • pH
• Operational conditions in the reactor
  • Feed caracteristics
    • Material
    • TS feed, %
    • TVS feed, %TS
  • Operational conditions
    • OLR (kgTVS/m3reactor day)
    • HRT (days)
    • Digester temperature, °C
  • Process parameters
    • pH
    • Alkalinity (@pH 6), gCaCO3/l
    • Alkalinity (@pH 4), gCaCO3/l
    • Volatile fatty acids, mgCOD/l
    • TS reactor, %
    • TVS reactor, %TS
  • Yields
    • GP, m3biogas/twaste
    • GPR, m3biogas/m3reactor day
    • SGP, m3CH4/kgTVSfeed
    • SGPsludge, m3CH4/kgTVSfeed
    • SGPofmsw, m3CH4/kgTVSfeed
    • CH4, %
    • TVS removal, %

Foreseen adjustment of the prototype considering the case of extruder technology can be done acting mainly on the following:

• extruder piston pressure (or cochlea speed);
• distance between piston (or cochlea) and the head of extrusion chamber;
• screen patterns (hole diameter and distribution).

While pressure regulation and feeding can be done continuously, changes in distance between piston and cylinder and subtitution of screens must be off-line, with mechanical operations.

Adjustments on mixer are about the height of suction pump require interventions, while calibration on rotation speed can be done online.

On digester there are mainly calibrations to be done (regulation of input flow, humidity and features and gas abstraction).

Optimisation of digestate dewatering require adjustment of polyelectrolyte processing.

Routine analyses of supernatants (PS DVS COD NH3 TKN Ptot) gives information about the need of ammonia stripping.

Constraints and assumptions

• Constraints
  • Test, measurement, characterization and calibration methods must comply with national and community rules
  • Adjustment, balancing and calibration must be completed on schedule in order to leave significant time for running the demonstration action.
• Assumptions
  • No disrupting change will occur in inflows (OFMSW and sludges) during test and adjusting
  • The internal laboratory is sufficient for most on-the-fly analyses
  • Turnover of key project resources is low.

Finally cogeneration will be activated with:

• adjustment of heating flow control;
• test and activation of electric power upload to the grid

Beneficiary responsible for implementation

P1 - SEARIS

Expected results

Main results of this action are

• overall environmental goal achieved as result of COWS full scale commissioning;
• sending of OFMSW to composting halted;
• energy needs internally satisfied (heating and power);
• production of surplus energy started
• COWS process validated, including
  • pre-treatmmet prototype optimal regime;
  • full COWS process running at full sludge and OFMSW inflow capacity

Deliverable D5 - COWS performance report will document the achievements.

Where and when

This action will take place at plant site in Viareggio.

Action start: 16/01/2015

Action end: 27/08/2015

Indicators of progress

• Schedule and effort variance;
  • actual vs. planned start/duration of tasks (if buffer time reserved for contingencies is to be used then remediation actions must be triggered);
  • actual vs. planned resource use (15% work overload and 5% budget variance are thresholds for triggering remediation actions)
• Performance (quality of delivered outputs based on lab analysis report)
  • environmental impact reduced as foreseen;
  • pre-treatment (COWS prototype) calibrated;
  • digester feeding calibrated;
  • OFMSW residual (post-separation) landfilling is at minimum.

Notes and References

<references />