5. Monitoring ZWD system

Monitoring is to evaluate the performance of ZWD system. Some parameters in the ZWD system that must be monitored are water quality and the growth performance of shrimp or prawn.

#### 5.1. Water quality parameter

Maintaining water quality is important in aquaculture system because water is habitat of aquatic animal so it should be monitored periodically. Factors that affect water quality are temperature, dissolved oxygen, pH, and inorganic nitrogen concentrations. Water quality parameters are divided into two groups: psychochemical and microbiological parameters.

#### 5.1.1. Psychochemical parameters

#### 5.1.1.1. Temperature

The optimum range of water temperature allows aquatic organisms to perform metabolism and growth. Temperature is an important water quality parameter, because it can affect the amount of dissolved oxygen budget in water and increase the rate of chemical reaction. If temperature value exceeds the tolerance limit of the cultures animal, then it leads the animal die. A good temperature range for aquaculture is 25–32C for the tropics [70]. The critical temperature for living water organisms ranges from 35 to 40C. Various regions in Indonesia have average air temperature during the day between 12.8–38C, and the difference depends on the elevation above sea level.

5.1.2. Microbiological parameter

Aquatic microbes have an important role in aquatic ecosystems. These microbes can affect the health of aquatic animals and occupy key positions in the food chain by providing edible nutrient for the next higher trophic level of aquatic life. In addition, the microbes assist the biochemical reactions that recycle most of the elements in the aquatic environment as well as in the soil. The amount of microbes in the water depends on the amount of organic compounds present in water body that usually interprets in biological oxygen demand (BOD) and chemical oxygen demand (COD) index. Higher organic matter causes dissolved oxygen content to be

Closed Aquaculture System: Zero Water Discharge for Shrimp and Prawn Farming in Indonesia

Production performance is also evaluated by a number of biological parameters. However, the list describes only for most priority parameters; there are survival rate (SR), average daily growth (ADG), total biomass (Wt), and food conversion ratio (FCR). Here are the formulas to

a. Survival rate is a survival index of cultured animals in a cultivation process from the beginning of the animal stocked until the animal harvested. Survival was calculated using

Where, SR = survival rate (%), No = initial shrimp number (ind), Nt = final shrimp number

b. Average body weight represents the average of individual weight for the entire shrimp population, it can be done by measuring individual shrimp weight that the numbers

> P<sup>n</sup> <sup>i</sup>¼<sup>1</sup> Wi

Where, ABW = average body weight (gr), Wi = body weight of the i-th shrimp (gr),

c. Average daily growth is average weight gained each day. ADG was calculated as follow:

ADG <sup>¼</sup> Wt � Wo

d. Total biomass is total weight of cultured animals at harvest. The total biomass was

Where, ADG = average daily growth (gr/day), Wt = total biomass at harvest (gr), Wo = total

� 100% (2)

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<sup>n</sup> (3)

<sup>t</sup> (4)

SR <sup>¼</sup> Nt No

ABW ¼

smaller because microbes use oxygen to oxidize organic matter.

calculate important biological parameters.

(ind), t = culture period (day).

calculated as follows:

equation:

5.2. Growth performance of shrimp or prawn: biological parameters

follow statistical rule (n). ABW was calculated as follow:

n = number of shrimp or prawn measured (ind)

initial biomass at stocking (gr), t = culture period (day).

#### 5.1.1.2. Dissolved oxygen (DO)

Dissolved oxygen is one of limiting factor for aquatic animals. Changes in oxygen concentration can have a direct effect to their respiration, if the oxygen is insufficient, the animal will be death. The number of organic compounds present in water body influences the amount of dissolved oxygen content. Organic compound is produced by microorganisms, consequently increasing biological oxygen demand (BOD), so that oxygen concentration is reduced in water body [71]. The minimum DO value that can be tolerated by crustacean is 4 mg/L, if less than that number, the shrimp will die. The recommended DO range for cultivation is 4–6 mg/L [44].

#### 5.1.1.3. pH

pH is a value for expressing the concentration of hydrogen ions (H+ ) in water. Water with a pH less than 4 and higher than 9.5 can cause death to living creatures and reduce aquatic productivity [71]. Water pH fluctuates with dissolved CO2 and has an inverse relationship pattern; the higher the CO2 content of the water, the pH will decrease and vice versa. This fluctuation will decrease when water contains CaCO3 salt. The tolerance for aquatic life to pH depends on many factors including temperature, dissolved oxygen concentration, variations of differentiated anions and cations, species, and biota life cycle. The nonoptimal pH of water affects the growth and reproduction [72].

#### 5.1.1.4. Inorganic nitrogen compounds

Inorganic nitrogen compounds are often found in water body in the form of ammonia, ammonium, nitrite, and nitrate. These compounds are strongly influenced by the oxygen content in water, when oxygen decreases, the ammonia formation increases. Naturally, the ammonia present in water is the result of animal metabolism and the decomposition of organic matter by bacteria. Ammonium tolerance for shrimp does not exceed from 3.95 ppm [9].

Another nitrogen form is nitrites. Naturally, such compounds are usually found in very little amount in water, because nitrite is unstable when there is oxygen. Other compounds are nitrate, which is the main nitrogen form in natural waters. Nitrate is one of the important compounds in the process of protein synthesis in animals and plants. The concentrations of nitrite and nitrate suggested in aquaculture were less than 25.7 ppm [73] and 200 ppm [22], respectively.

#### 5.1.2. Microbiological parameter

amount of dissolved oxygen budget in water and increase the rate of chemical reaction. If temperature value exceeds the tolerance limit of the cultures animal, then it leads the animal die. A good temperature range for aquaculture is 25–32C for the tropics [70]. The critical temperature for living water organisms ranges from 35 to 40C. Various regions in Indonesia have average air temperature during the day between 12.8–38C, and the difference depends

Dissolved oxygen is one of limiting factor for aquatic animals. Changes in oxygen concentration can have a direct effect to their respiration, if the oxygen is insufficient, the animal will be death. The number of organic compounds present in water body influences the amount of dissolved oxygen content. Organic compound is produced by microorganisms, consequently increasing biological oxygen demand (BOD), so that oxygen concentration is reduced in water body [71]. The minimum DO value that can be tolerated by crustacean is 4 mg/L, if less than that number, the shrimp will die. The recommended DO range for

less than 4 and higher than 9.5 can cause death to living creatures and reduce aquatic productivity [71]. Water pH fluctuates with dissolved CO2 and has an inverse relationship pattern; the higher the CO2 content of the water, the pH will decrease and vice versa. This fluctuation will decrease when water contains CaCO3 salt. The tolerance for aquatic life to pH depends on many factors including temperature, dissolved oxygen concentration, variations of differentiated anions and cations, species, and biota life cycle. The nonoptimal pH of water affects the

Inorganic nitrogen compounds are often found in water body in the form of ammonia, ammonium, nitrite, and nitrate. These compounds are strongly influenced by the oxygen content in water, when oxygen decreases, the ammonia formation increases. Naturally, the ammonia present in water is the result of animal metabolism and the decomposition of organic matter

Another nitrogen form is nitrites. Naturally, such compounds are usually found in very little amount in water, because nitrite is unstable when there is oxygen. Other compounds are nitrate, which is the main nitrogen form in natural waters. Nitrate is one of the important compounds in the process of protein synthesis in animals and plants. The concentrations of nitrite and nitrate suggested in aquaculture were less than 25.7 ppm [73] and 200 ppm [22],

by bacteria. Ammonium tolerance for shrimp does not exceed from 3.95 ppm [9].

) in water. Water with a pH

pH is a value for expressing the concentration of hydrogen ions (H+

on the elevation above sea level.

310 Biological Resources of Water

5.1.1.2. Dissolved oxygen (DO)

cultivation is 4–6 mg/L [44].

growth and reproduction [72].

5.1.1.4. Inorganic nitrogen compounds

5.1.1.3. pH

respectively.

Aquatic microbes have an important role in aquatic ecosystems. These microbes can affect the health of aquatic animals and occupy key positions in the food chain by providing edible nutrient for the next higher trophic level of aquatic life. In addition, the microbes assist the biochemical reactions that recycle most of the elements in the aquatic environment as well as in the soil. The amount of microbes in the water depends on the amount of organic compounds present in water body that usually interprets in biological oxygen demand (BOD) and chemical oxygen demand (COD) index. Higher organic matter causes dissolved oxygen content to be smaller because microbes use oxygen to oxidize organic matter.

#### 5.2. Growth performance of shrimp or prawn: biological parameters

Production performance is also evaluated by a number of biological parameters. However, the list describes only for most priority parameters; there are survival rate (SR), average daily growth (ADG), total biomass (Wt), and food conversion ratio (FCR). Here are the formulas to calculate important biological parameters.

a. Survival rate is a survival index of cultured animals in a cultivation process from the beginning of the animal stocked until the animal harvested. Survival was calculated using equation:

$$SR = \frac{Nt}{No} \times 100\% \tag{2}$$

Where, SR = survival rate (%), No = initial shrimp number (ind), Nt = final shrimp number (ind), t = culture period (day).

b. Average body weight represents the average of individual weight for the entire shrimp population, it can be done by measuring individual shrimp weight that the numbers follow statistical rule (n). ABW was calculated as follow:

$$ABW = \frac{\sum\_{i=1}^{n} W i}{n} \tag{3}$$

Where, ABW = average body weight (gr), Wi = body weight of the i-th shrimp (gr), n = number of shrimp or prawn measured (ind)

c. Average daily growth is average weight gained each day. ADG was calculated as follow:

$$ADG = \frac{Wt - WO}{t} \tag{4}$$

Where, ADG = average daily growth (gr/day), Wt = total biomass at harvest (gr), Wo = total initial biomass at stocking (gr), t = culture period (day).

d. Total biomass is total weight of cultured animals at harvest. The total biomass was calculated as follows:

$$\mathcal{W}t = \sum\_{i=1}^{n} \mathcal{W}\ddot{\imath} \tag{5}$$

Water quality during 90-day cultivation period was still in tolerance levels for white shrimp in both systems, as seen in Table 5. As a concern, threshold value of ammonium in ZWD systems was higher than batch system, it was 0.69 ppm compared to 0.59 ppm, but it was not significantly different (p > 0.05). High ammonium level was caused by higher feed input in the ZWD system, it was about 44% compared to the batch system. A large feed input would affect the increment of ammonium level in culture, but ZWD system has rapid ammonium breakdown capacity that was accomplished through microbial manipulation. Moreover, nitrite level also did not differ significantly in both systems. These levels suggested that the ammonium and nitrite breakdown capacity of ZWD systems are higher than batch system. In addition, better ammonium and nitrite breakdown capacity were shown through nitrate level that was higher in ZWD system after 90-day culture period. The nitrate level in ZWD system reached 42.9 mg/L,

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Besides the benefits of nitrifying bacteria and microalgae in maintaining water quality, they also indirectly inhibit pathogenic bacteria Vibrio spp. growth. Microbiological assessment shown that excessive organic matter did not increase the number of Vibrio spp. Previous research reported that marine diatom, such as C. calcitrans, has the ability to secrete fatty acids and esters, antibacterial compounds which inhibit several heterotrophic bacteria growth, such as Vibrio spp. [74]. Another analysis of predominant bacteria found in shrimp cultivation using ZWD system reported that the water contained following species, based on the most dominant bacteria found B. flexus, Geobacillus stearothermophilus, five species of Bacillus sp., Pseudomonas oleovorans, Pseudomonas peli, and Xenorhabdus nematophilus [66]. Bacillus sp. known as probiotic bacteria suggested that ZWD system not only achieved acceptable psychochemical parameters, but also microbiological parameters support

Research conducted for grow out white shrimp cultivation using ZWD system at industrial scale has been applied in UD. Populer, Gresik, East Java [50]. The research used PL-17 white shrimp as cultured animal at low salinity water (5 ppt) in ZWD system. Culture period was 70 days for three different stocking densities; there were 200, 300, and 400 ind/m<sup>3</sup> further

Parameter Batch ZWD Tolerance range

<sup>4</sup> (mg/L) 0.20–0.59 0.07–0.69 < 3.95 mg/L [9]

<sup>2</sup> (mg/L) 0–3.20 0–3.15 < 25.7 mg/L [73]

<sup>3</sup> (mg/L) 1.38–14.17 1.04–42.9 < 200 mg/L [22]

pH 7.63–8.80 4–9.5 [71] DO (mg/L) 7.42 � 0.52 6.81 � 0.5 > 4 mg/L [44]

Table 5. Water quality measurement during 70-day culture period [13].

Temperature (�C) 25.96–30.63 25–32�C for tropic area [70]

while in batch system, it was 14.17 mg/L.

shrimp growth as well.

referred as SD200, SD300, and SD400.

6.1.2. Industrial scale

NH<sup>þ</sup>

NO�

NO�

Where, Wt = total biomass (gr), Wi = body weight of the i-th shrimp (gr)

e. Food conversion ratio (FCR) indicates a ratio of efficiency of feed, which is converted into animal body mass. FCR was calculated as follow:

$$FCR = \frac{\text{Total feed given during culture period (kg)}}{\text{Total biomass (kg)}} \tag{6}$$
