APPENDIX N Wastewater Treatment Strategy Concept Paper

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1 OMNICANE ETHANOL PRODUCTION LTD Installation and Operation of a Distillery and Concentrated Molasses Solids (CMS) Fertilizer Blending Plant at Omnicane Sugar Cluster - La Baraque Environmental Impact Assessment APPENDIX N Wastewater Treatment Strategy Concept Paper

2 OMNICANE MILLING OPERATIONS (LA BARAQUE) LTD Factory Effluent Management Strategy and Action Plan 1. Centralisation of Activities on La Baraque One of the major components of the Multi Annual Adaptation Strategy (MAAS ) is the centralization of milling activities and the production of refined sugar so as to reduce the cost of production and at the same time generate value added products respectively. In this context, the La Baraque sugar factory has undergone major changes as enumerated below as from a) The cane crushing capacity at La Baraque has increased from 135 ton/hr in 2006 to 350 ton/hr in 2007 as a result of the centralization of the milling activities in the southern part of Mauritius b) As from 2007, there was to be no bagasse combustion at La Baraque sugar factory and hence no ash treatment since the bagasse would henceforth be used at the adjacent thermal power plant (Omnicane Thermal Energy Operations Ltd Ex- CTSAV) c) In 2007, the traditional mills used for juice extraction were replaced by the first diffuser to be installed in a sugar factory in Mauritius d) As from 2007, the pan boiling process for sugar crystallisation was transformed from a batch process into a continuous process e) In 2008, the sulphitation process was implemented to reduce the colour in the raw sugar before it could be further refined f) As from the start of crop 2009, Union St Aubin factory stopped producing sugar and instead it started producing 65,000 tons of syrup which is sent to La Baraque factory for further processing g) In 2009, the La Baraque sugar refinery was constructed and became operational towards the end of the year With regard to f), as from crop 2011, with the closure of Union St Aubin factory it is expected that 300,000 tons of cane from the Union St Aubin catchment area will be processed at La Baraque, hence point f) will will be superseded. Page 1 of 8

3 2. La Baraque Factory Effluents With all these changes brought about by the centralization of milling operation, it became obvious that the effluent characteristics obtained until the end of crop 2006 would be significantly different from the new set up at la Baraque factory as from The implementation of a pollution abatement programme for the effluents from the sugar milling operation requires inter alia: Wastewater characteristics and its variability; Different wastewater flows, their pattern and varability.. It is in this context that a thorough effluent characterization programme was initiated in 2007 with the support of the MSIRI. 2.1 Effluent characterization The aims and objectives of the effluent characterization study conducted between 2007 and 2009 were to: Identify and characterize all effluent streams in terms of quantity and quality Identify and implement measures to minimize the effluent generation from each stream Predict the long term effluent characteristics expected from La Baraque sugar factory The characterization study carried out so far over crop 2007, 2008 and 2009 has shown considerable improvements in the quality of effluents from La Baraque sugar processing activities. After each time period, once measures were identified to reduce effluent generation, they were implemented and subsequently their impacts on the pollutants load were assessed. Observations made on the pollutant reduction measures have shown that not only significant pollutant load reduction (for example COD load)was achieved but also reduction of their variability over time. Such improvements have been possible with optimized process parameters, implementation of good Page 2 of 8

4 housekeeping, minimization of water consumption, and implementation of recycling/recovery options wherever possible. FINAL EFFLUENT COD IN COD (mg/l) Page 3 of 8

5 700 FINAL EFFLUENT COD IN COD (mg/l) /2/ /4/ /6/ /8/ /10/ /12/ /14/ /16/ /18/ /20/ /22/ /24/ /26/ /28/ /30/ /2/ /4/ /6/ /8/ /10/ /12/ /14/ /16/ /18/2009 From the above two graphs it is observed that there has been a significant improvement in the quality of the final effluent from La Baraque from 2007 to It is worth noting that this improvement has been possible through considerable improvements being brought about within the factory with the support of each department. Furthermore, it must be said that the factory operations has stabilized after teething problems encountered during the first crop of 2007 following expansion and centralization. 2.2 Refinery Effluents as from December 2009 The only component of the La Baraque factory complex whose effluents still needed to be characterized by end of 2009 was the newly constructed sugar refinery. In fact the refinery came into operation only as from November 2009 and is still adjusting to some teething problems related to the start up. Since the refinery would operate year round during both crop and off crop season, it was vital to monitor the refinery effluents over both periods to be able to predict the long term effluent characteristics Refinery Scum The characterization study has shown that the liquid scum resulting from syrup clarification in the refinery represents the major source of sugar Page 4 of 8

6 entrainment with an associated COD.. During crop this scum is recirculated into the diffuser while during intercrop its disposal was a major issue. After several trials using different dewatering techniques it was concluded that the belt filter provided the best alternative. Hence, in December 2010, a belt filter has been installed at the refinery to dewater the sludge such that the permeate can be recycled while the solid residue can be returned back to the fields. 2.3 Characterization in 2010 The characterization study in 2010 was conducted with the support of MSIRI and lasted from October to November The drawing below shows the different water streams that have been sampled for both flow and quality. Page 5 of 8

7 Catchment area of waste water streams at Omnicane Milling/Refinery Raw Water Input CTSAV Overflow Weir H FINAL EFFLUENT DRAIN MILLING Steam REFINERY Cameco + Pre-ext mill Mill Drain Scums Barometric Condenser Washings : Centrifugals, Xtallisers, & Bagasse Conveyors Mill Bearings Cooling Tower 2 Refinery Effluents: Condenser overflow, Chemical cleaning, & Overflow industrial & Process water Refinery Effluents: Washing, Backwash of IER and DBF, and Melter Oil & grease trap CV P E 6 Outlet Oil &Grease trap Condenser drain (+ overflow basin) Process drain 1 7 Cooling Tower 1 A F Overflow 5 D 2 B I 8 3 G 9 C 4 Sampling points Flow measurement The study identified a number of areas where improvements can be brought during intercrop namely to: 1. Minimise sugar loss 2. Further reduce the pollution load being generated from the refinery and raw house 3. Avoid contamination of condensed water streams 4. Further reduce the volume of water to be treated by promoting segregation of clean water streams 3. Actions for Intercrop 2011 A summary of actions to be implemented during intercrop is listed hereunder. Placing of nets above the diffuser in feed carrier to avoid bagasse spillage. This will avoid contamination of the mill drain Placing of nets around second dewatering mill to avoid bagasse spillage. Reduce contamination of process drain Improve bagasse chute to CTSAV belt. This will avoid comtamination of process drain caused by bagasse spillage Page 6 of 8

8 Installation of nozzles for Sunday cleaning of evaporators. This will minimize the volume of Sunday washings generated Modifications to provide condensate from Evaporator K2 to Steam Transformer during crop. This will avoid contamination of condenser drain Modifications to melters and recovery syrup scale to reduce contamination of refinery effluents The investment cost of the above works is estimated to be around Rs 2.5M. 4. Implementation of the treatment phase I: Our consultant is presently working on the design of Phase 1 of the project which is expected to be implemented by end of September Phase 1 will comprise of: Segregation and separate channeling of the clean water streams and polluted streams. The clean water streams targeted are: a. condenser drain (caters for overflow from cooling tower, barometric condenser, and overflow of raw water from bassin usine) Estimated volume 100 m3/hr b. mill bearing drain which mainly collects water from cane yard and groundwater ingress into cane feed table Estimated volume 40 m3/hr c. CVP cooling tower overflow Estimated volume 60 m3/hr The volume of clean water to be collected separately from the polluted effluents is expected to be around 200 m3/hr. This water will bypass the treatment plant and will be sent directly to the irrigation network Construction of a Sunday washings collection tank This tank will collect the Sunday washings characterized by high sugar and ph. The tank s design is being worked out but it is expected to be around 1,500 m3 capacity with an aeration system to keep the effluent in aerobic conditions. Construction of a homogenization and pretreatment unit This tank will receive 100 m3/hr of effluents from the process and refinery drains. It will also receive over week days the effluent from the Sunday washings collection tank at the rate of m3/hr. Page 7 of 8

9 This unit will be designed for an average flow of 150 m3/hr to cater for the acid condensate of the distillery plant which is expected to be generated at the rate of m3/hr. 5. Location of the Treatment Plant The treatment plant will be located next to the cooling tower located on Souffleur road on land belonging to Savannah SE. An area of 1.5 Ha presently under cane cultivation will need to be acquired/leased from Savannah SE to build the treatment plant. 6. Post Phase I Actions Characterization of effluents : This stage will be crucial in assessing: 1. The impacts of the cleaner production measures implemented 2. The effluents characteristics both in terms of quality and quantity 3. The level of pollution abatement being achieved Implementation of the phase II The results of the characterization study for will allow the determination of the feasibility of various options for the pollution abatement and the establishment of the water quality of the treated effluent in conformity with the local regulations. Depending on the characteristics of the wastewater and their associated pollutant loads (COD, BOD5, etc.), two main options will be investigated: Anaerobic digestion with the possibility of production of renewable energy from biogas generation; Aerobic polishing of the effluents so that the treated effluent conforms to its reuse for irrigation. Hence based on the characterization study of , implementation of phase II will follow. Page 8 of 8