Proceedings of the 19th IAHR-APD Congress 2014, Hanoi, Vietnam ISBN 978604821338-1 INTEGRATED WASTEWATER TREATMENT: NUTRIENT STRIPPING RATE OF SEEWEED,GracilariaVerrucosaFROM INTENSIVE SHRIMP FARMING WASTEWATER NGUYEN QUANG LICH(1), MARTIN KUMAR(2), BALAJI SESHADRI(3,4), NANTHI BOLAN(3) (1) Department of Agricultural Engineering, Hue University of Agriculture and Forestry, Hue city, Vietnam quanglichckcn@huaf.edu.vn (2) (3) School of Biology, Flinders University, Adelaide, South Australia, Australia martin.kumar@senet.au.com Centre for Environmental Risk Assessment and Remediation, University of South Australia, South Australia, Australia nanthi.bolan@unisa.edu.au (4) Cooperative Research Centre for Contamination Assessment and Remediation of the Environment, South Australia, Australia balaji.seshadri@unisa.edu.au ABSTRACT This study explored the potential of Gracilaria verrucosa, one of the most common seaweed species in Tam Gang lagoon in order to determinethe nutrient removal efficiency over eight days of treatment of wastewater in an intensive shrimp farm 1000 liters of wastewater from intensive shrimp farming after enhancing dissolved oxygen (DO) level and removing ammonia (NH 3) toxicity by splash board treatment over three hours was transferred into the treatment tank The tank was stocked with 500 g of Mugil cephalus and 200 g of Cerithidea obtuse for biodegradation of organic matter After 84 hours of biodegradation of organic matter, the wastewater was moved into four different treatment tanks (250 L) that were stocked with three different levels of G verrucosa biomass: 300 g/m3 (G-300), 400 g/m3 (G-400) and 500 g/m3 (G-500) and a control (CT) The removal efficiency of total ammonium nitrogen (TAN) increased with increasing seaweed biomass and ranged from 300-500 g/m The final TAN removal rates were 89%, 95.6% and 98.1% in treatment G-300, G-400 and G-500, respectively The removal of total nitrogen (TN) increased from 40.3% to 64.1% with increasing G verrucosa biomass from 300 - 500 g/m3 The PO4-P decreased from 0.91 mg/L to < 0.42 mg/L in all G verrucosa biomass treatments The highest total phosphorus (TP) stripping was achieved in treatment G-500 (72.5%), followed by treatment G-400 (66.5%) and G-300 (59.8 %) The study demonstrated that the seaweed, G verrucosa treatment significantly reduced both N and P concentration in shrimp wastewater and the nutrient removal efficiency increased with increasing seaweed biomass level Keywords:shrimp effluent, wastewater treatment, nutrient, seaweed 1 INTRODUCTION The rapid development of intensive shrimp farming has had an adverse impact on the environment, through the conversion of large mangrove areas into shrimp ponds In the last decade, several studies found that only 20% of nutrients added through feed were converted to harvesting shrimp, while more than 50% was discharged into the environment (Briggs & Funge-Smith 1994; Funge-Smith, 1998; Jackson, 2003; Long & Toan, 2008) Therefore, improvement in the pond’s processing of nutrients and improved design and management of effluent treatment systems has been developed during this period An integrated biological treatment system approach offers an environmentally friendly solution to manage nutrient waste from intensive aquaculture farming In recent years, many researchers focused on using aquatic plants such as seaweed for the removal of nutrients in recirculating aquaculture systems A review of publications over the past 30 years decade suggested that seaweed could be used to reduce the nutrient (N and P) content of wastewater They can concentrate nutrients by a factor of up to 105 over seawater levels (Beardall, 1997; Lobban, 1994) and also respond to increased nutrient availability by augmenting internal stores Many kinds of seaweeds cannot only take up NH 4-N in the form of N for their growth, but also have the ability to take up more P than they require for maximum growth in most wastewater (Baruah, Norouzitallab, & Sorgeloos, 2007) Buschmann et al (1996) used Gracilaria chilensis for removing dissolved nutrients from outdoor intensive salmon tank cultures (8 m tank for salmon) and noticed that the production of this seaweed species was 48.9 kg/m2.year and also removed 50% of dissolved nutrients in winter, increasing to 90 − 95% in spring season Jones et al (2002) very successfully used Gracilaria edulis for treatment of wastewater from shrimp farming The concentration of TN and TP were reduced 41% and 52%, respectively (over 90% removal of NH 4N, NO2-N, NO3-N and PO4-P) MarinhoSoriano et al (2009b) examined another type of Gracilaria species (Gracilaria birdiae) for production of useful algal biomass and removal of nutrients from shrimp pond effluent in Brazil The results obtained showed a gradual increase in biomass and relative growth rate over the experimental period The concentration of NH4+ decreased by 34%, NO3-Nby 100% and PO4-P by 93.5% in four weeks (Marinho Soriano, Nunes, Carneiro, & Pereira, 2009) These studies suggest that it is possible to economically cultivate valuable seaweed using aquaculture wastewater and at the same time successfully remove nutrients Shrimp farming is the most economically successful enterprise in Tam Giang lagoon zone However, this activity has caused major environmental pollution by discharging large amount of nutrients and sediment in the lagoon during the production cycle Biological treatment method involving aquatic animals and plants as natural biofilters in order to remove the nutrients from intensive shrimp farm wastewater is environment friendly and cost-effective approach It is widely recognized that development of sustainable shrimp farming practices would produce significant economic benefit for any developing country such as Vietnam There are many important species of algae with potential that can be used for aquaculture The seaweeds include red, brown and green algae Briggs et al (1993) and Zhou et al (2006) reported that Gracilaria is the most effective seaweed species for recovering nutrients from aquaculture water The species not only has high ability for reducing nutrient levels in aquaculture effluents, but also has a high value for agar production and high nutritional value for humans, animals or plants (Briggs et al., 1993) Gracilaria verrucosa (G verrucosa) is the most common species of the Gracilaria family in the Tam Giang lagoon system (Tra, 1989) Dawes et al (1984) and Tra(1989) reported that G verrucosa is able to adapt to a wide range of ecological conditions (5-380C for temperature, 3-35‰ for salinity and pH from 7.4-8.5), with fast growth rate, long annual culture time (2-3 months), high production rates, good gel quality and capacity for harvesting several times a year G verrucosa can live in mud or silt bottom with light intensity ranging from 50-30,000 lux and showed high capacity for reducing nutrient levels from shrimp farm effluent (Huo et al., 2011; Izzati, 2012) In addition, G verrucosa is also a genus of red algae notable for its economic importance as an agarphyte as well as a food for humans and various species of shellfish The objective of this study was to determine the nutrient stripping efficiency of G verrucosa from intensive shrimp farming wastewater MATERIALS AND METHODS The experiment was conducted to optimize the density of seaweed biomass for maximizing nutrient removal from shrimp effluent Seaweed was tested at three biomass values 300 (GV-300), 400 (GV-400) and 500 (GV-500) g/m3 and control (CT) (0 g/m3) The experiment was conducted over eight days and replicated three times from 2-30 May 2011 at Dien Mon enterprise shrimp farming, located in Quang Dien district, ThuaThien Hue province, Vietnam Wastewater from shrimp farms after enhancing DO and removing NH3toxicity by a splash board treatment over three hours was then pumped into tanks which were stocked with 500 g of Mugil cephalus and 200 g of Cerithidea obtuse for biodegradation of organic matter during an 84 hour period and finally moved into the batch exchange before being used for this experiment One m of wastewater was supplied into each treatment tank The oxygen level in the treatment tanks was maintained at > mg/L during the experimental process The effects of seaweed biomass on ammonia and nutrient removal (NO2-N, NO3-N, TN, PO4-P and TP) were investigated during the eight day treatment process Water samples were taken at 25 ̶ 30 cm in depth (from the water surface) at five different positions inside the tank including the four corners and the center The collected samples were homogeneously mixed together to make one litre of composite sample This sample stored in a L polyethylene amber bottles and various parameters were transported immediately in insulated coolers to be chemically analysed at a laboratory Water parameters including T, pH, DO, S, total ammonia nitrogen (TAN) and NO2-N were analyzed daily in the field while other parameters including NO 3-N, PO4-P, TN and TP were measured every two days of the treatment process in the laboratory while it increased by 20.62% in the control within days of experimentation To analyze the nutrient removal efficiency of different seaweed biomass, experiment was replicated three times to get reliable data Descriptive statistics of the effluent water quality indicators of three seaweed biomass are presented using the mean and the standard deviation (SD) values during the treatment period For optimizing seaweed biomass, one way ANOVA followed by Tukey post hoc test have been used for analysis as well as for finding the significant differences between the three densities for each species and among five treatment types including treatments and the control SPSS software Version 21 was used to analyze the data The values of significance for all comparisons of treatments used were p < 0.05 RESULTS The effects of G verrucosa biomass on the fluctuation of T, pH, S and DO are summarized in Table Table Mean (± SD) values of water T, pH, S and DO at three different G verrucosa biomass levels (300, 400 and 500 g/m3) and a control during days treatment Mean values within the same column with the same superscripts are not significantly different at p0.05) However, in the control, NO2-N did not change in the first two days of treatment, but after this period it significantly increased until the end of treatment The final concentration of NO2-N in the control was 5.25 mg/L, increasing by approximately 20.61% compared to initial value and significant differences were found between the treatments and the control (p