Water and air quality measuring system

#include<LiquidCrystal.h> 
LiquidCrystal lcd(2, 3, 4, 5, 6, 7);

#define samp_siz 4
#define rise_threshold 4
#define sensor_pin A0
int sensorPin = 9; 
int sensorValue;
int read_ADC;
int ntu;

// make some custom characters:
byte heart[8] = {
  0b00000,
  0b01010,
  0b11111,
  0b11111,
  0b11111,
  0b01110,
  0b00100,
  0b00000
};

byte smiley[8] = {
  0b00000,
  0b00000,
  0b01010,
  0b00000,
  0b00000,
  0b10001,
  0b01110,
  0b00000
};

byte frownie[8] = {
  0b00000,
  0b00000,
  0b01010,
  0b00000,
  0b00000,
  0b00000,
  0b01110,
  0b10001
};

byte armsDown[8] = {
  0b00100,
  0b01010,
  0b00100,
  0b00100,
  0b01110,
  0b10101,
  0b00100,
  0b01010
};

byte armsUp[8] = {
  0b00100,
  0b01010,
  0b00100,
  0b10101,
  0b01110,
  0b00100,
  0b00100,
  0b01010
};
 
void setup(){// put your setup code here, to run once 
pinMode(sensor_pin, INPUT);

lcd.begin(20, 4); // Configura lcd numero columnas y filas
lcd.clear();
lcd.setCursor (4,0);
lcd.print("!!Welcome!!");
lcd.setCursor (2,1);
lcd.print(" T.AQI Project"); 
lcd.setCursor (0,2);
lcd.print(" Made By Thashwanth"); 
lcd.setCursor (6,3);
lcd.print("Arumugam"); 
delay(7000);
lcd.clear();
  // create a new character
  lcd.createChar(0, heart);
  // create a new character
  lcd.createChar(1, smiley);
  // create a new character
  lcd.createChar(2, frownie);
  // create a new character
  lcd.createChar(3, armsDown);
  // create a new character
  lcd.createChar(4, armsUp);

  // set the cursor to the top left
  lcd.setCursor(6, 3);
  delay(2000);
  // Print a message to the lcd.
  lcd.print("Welcome!");
  lcd.write((byte)1);
  delay(2000);
}
 
void loop(){
  
read_ADC = analogRead(sensor_pin);
if(read_ADC>208)read_ADC=208;

ntu = map(read_ADC, 0, 208, 300, 0); 
 
lcd.setCursor(0,0);
lcd.print("Turbidity: ");
lcd.print(ntu);
lcd.print("  ");
lcd.setCursor(4,3);
lcd.write((byte)4);
lcd.print("!Welcome!");
lcd.write((byte)1);

lcd.setCursor(0,1);//set cursor (colum by row) indexing from 0
if(ntu<20)            lcd.print("Water Very Clean");
if(ntu>=20 && ntu<50) lcd.print("Water Norm Clean");
if(ntu>=50)           lcd.print("Water Very Dirty");

delay(2000);

  sensorValue = analogRead(A1); // read analog input pin 0
  lcd.clear();
  lcd.setCursor(0,2);
  lcd.print("Air Quality:");
//  lcd.setCursor(0,8);
  lcd.print(sensorValue);
  Serial.print(sensorValue);
  if (sensorValue <= 100)
  { 
    lcd.setCursor(15,2);
    lcd.print("Good");
  }
  else if (sensorValue >= 100 && sensorValue < 150){
    lcd.setCursor(15,2);
    lcd.print("Poor");
  }
  else {
    lcd.setCursor(15,2);
    lcd.print("Toxic"); 
  }
}