« Potential of bio diesel production from scraped coconut refuse for agricultural tractors | Home | Present status of the tsunami affected home gardens: A case study at Madiha in Matara District, Southern Sri Lanka »
Characterization and removal of pollutants in soak water resulting from parboiling of paddy.
By Admin | July 11, 2009
Parboiling is a process used to improve the milling characteristics of paddy. Various parboiling methods are practiced in Sri Lanka. Depending on the parboiling method, paddy is soaked for different periods. A significant amount of water is consumed for this soaking process. The two main methods of soaking are hot soaking and cold soaking.
Hot soaking method is adopted by most rice mill owners in Sri Lanka. These mills generate wastewater which has adverse environmental impacts. This paper presents characteristics of wastewater generated from hot soaking and cold soaking operations of two varieties of paddy namely red rice (LD 356) and white rice (BG 300). These varieties are commonly available in Sri Lanka. The possibility of removing pollutants from the parboil wastewater was also investigated.
Depending on the soaking method effluent characteristics vary. Important characteristics of the effluent such as Chemical Oxygen Demand, Biological Oxygen Demand, Total Suspended Solids, Total Microbial Count, Total Phosphorous and pH were determined. pH values of wastewater samples generated from hot soaking of paddy are slightly acidic and showed values close to neutral value. Soak water from cold soaking method exhibited pH values around 5.5, slightly acidic than hot soaking water. The results showed that COD and BOD values in soak water resulting from both soaking methods were higher than the discharge standards. Soak water from both hot soaking and cold soaking of red rice variety showed relatively higher COD and BOD values compared to soak water from white rice. In cold soaking, red rice soak water had COD in the range 6000 8000 mg/l while white rice soak water had COD between 4000 5000 mg/l. BOD of soak water varied between 900 and 2080 mg/. Suspended solids in soak water were volatile at 550OC. Microbial population was higher in cold soaking than in hot soaking from both varieties of rice.
COD of soak water resulting from hot soaking of red rice was reduced to half of its initial value by micro organisms present in soak water after 2 days aerating at C:N:P ratio of 100:5:1. Cultures prepared using rice straw and cow dung as microbial sources, were able to remove 75 % of COD in 3 days. Rice straw and cow dung showed approximately same removal rate of COD.
Key words: wastewater, paddy parboiling, pollutant removal, hot soaking
Gayanee Karunaratne, Manisha Gunasekera
Department of Chemical and Process Engineering, University of Moratuwa, Sri Lanka.
Topics: symposium2008 | 1 Comment »
March 13th, 2010 at 7:56 pm
What are the prctical applications for this problem? Because we have to implement cheap and easy method to treat the water before disposal or further use.
Further more the environment effects should explain better than marginalize the outcomes. As a fact need further research on what kind of soaking and boiling techniques been use(tank,boiling barrels,steamers) also the ways the water being disposed to get the bigger picture to implement the realistic practical solution for the problem