Impacts of Aquaculture and Domestic Wastewater on the Water Quality of Santubong River, Malaysia

Developments along the Santubong River basin may have an impact on the aquatic ecosystem. To determine the impacts of activities on the water quality, ten stations were selected for water quality study over 9 months. Results show that salinity increases from 14.0 PSU upstream to 30.4 PSU downstream. Lowest DO range was 2.3-4.1 mg/L. TSS ranged was 20-135 mg/L and the highest was observed near construction and residential areas, the second and third highest near shrimp culture discharge areas. BOD5 was the highest near construction and residential areas. BOD5 of a station near shrimp culture was not significantly different from the residential areas. Two stations near shrimp culture site also recorded the highest Chl-a. The highest ammonia-nitrogen, nitrite-nitrogen and reactive phosphorus were observed at stations near shrimp farm sites whereas nitrate-nitrogen was the highest near construction and residential areas. Cage culture site showed the highest phosphorus and second highest nitrite-nitrogen and ammonia-nitrogen. This study showed that TSS and BOD5 were elevated near residential and construction areas and nutrients were elevated near shrimp farm sites resulting in algal bloom. Therefore, it is recommended that residential and shrimp farm discharge be treated to acceptable quality before discharge to protect the aquatic resources.

Water Quality and Loading of Pollutants from Shrimp Ponds during Harvesting

Shrimp aquaculture is an important source of revenue for the state of Sarawak, Malaysia. However, there were concerns on the impact of shrimp farming on the mangrove ecosystem due to the discharge of shrimp pond water to the surrounding environment and potential self-pollution through the intake of surrounding water for the shrimp ponds. Therefore, the objectives of this study were to determine the water quality of the harvesting pond water and quantify the pollutants loadings. Samplings were conducted in three ponds and three channels near the pond outflow in a commercial shrimp farm during complete draining of water at harvest. Results indicated that TSS and Chl-a were high in both the ponds and channels. Total ammonia-nitrogen was the predominant form of the inorganic nitrogen and the mean values in both the ponds and channels were more than 1 mg/L which exceeded the maximum recommended for fish. Therefore, the water quality of the ponds and channel indicate that pond effluent should not be discharged directly into the surrounding environment but treated and nutrients recovered. Loads of total suspended solids, BODs, inorganic nitrogen, ammonia nitrogen, soluble reactive phosphorus and Chl-a of the effluent were quantified.